CHEMICAL NOTES: ORGANIC BY WILLIAM J. GIES NEW YORK 1904 CHEMICAL NOTES: ORGANIC BY WILLIAM J. GIES NEW YORK 1904 Copyright, 1904 By WILLIAM J. GIES Press or The New Era Printing Comraby, Lancaster, Pa PREFACE. This little volume of notes on the elements of organic chemistry has been prepared for the benefit of students who take the second half of the course in general chemistry at the College of Physicians and Surgeons. The contents of this volume supplement the author's lectures and the laboratory work in organic chemistry. The student is expected to take ample notes of the lectures, demon- strations and experiments of the course. He will recite twice a week on the personal instruction he has received in the lecture room and in the laboratory, and, also, on prescribed sections of these notes. William J. Gies. Laboratory of Physiological Chemistry, College of Physicians and Surgeons, Columbia University, December 10, 1904. III CONTENTS. INTRODUCTION ^7 CHAPTER I. General chemical constitution of organic SUBSTANCES 24 CHAPTER II. General physico-chemical properties of ORGANIC SUBSTANCES 44 CHAPTER III. The paraffins ....... 51 CHAPTER IV. Halogen derivatives of the paraffins . 68 CHAPTER V. Oxygen derivatives of the paraffins. I. Alcohols CHAPTER VI. Oxygen derivatives of the paraffins. II. ETHERS 88 CHAPTER VII. Oxygen derivatives of the paraffins. III. Aldehydes and ketones . . . .94 CHAPTER VIII. Oxygen derivatives of the paraffins. IV. Fatty acids 114 [First Part.] V INTRODUCTION COMPARATIVE ELEMENTARY COMPOSITION OF THE MINERAL AND BIOLOGICAL KINGDOMS. I. Oxygen. In our study of inorganic chemistry we learned that there are very conspicuous differences between the elementary composition of the mass of the mineral kingdom (the earth's crust, including air and water), on one side, and of the mass of the biological kingdom (plants and animals), on the other. This difference is indicated by the figures in the tables on page 9. The comparative percentage data in the tables on page 9 show that oxygen is by far the predominant element in each kingdom. They show also that there is no particular similarity between the proportions of any of the other elements composing the two kingdoms.* 2. Silicon and Carbon. The most conspicuous element next to oxygen in the mineral kingdom is silicon. The most abundant element next to oxygen in the biological kingdom is carbon. Both silicon and carbon unite readily with oxygen. The mineral king- dom consists in the main of compounds containing oxygen and silicon. The biological kingdom consists chiefly of compounds containing oxygen and carbon. Carbon and silicon are, in many respects, closely related elements. The form and nature of the compounds of carbon and silicon are very much alike.f Carbon and silicon do not, however, occur in * Calcium happens to be fifth in the order of quantity in each of the tables on page 9. This fact is without any particular significance, however. f Silicon hydrid, SiH4, like methane, CHt (60), doesnot manifest acid proper- ties, but silica, SiO2, like carbon dioxid, CO2, exerts feeble acid properties. These similarities are typical of the general agreement between the compounds of silicon and carbon. "In addition to this resemblance, silicon presents one exceedingly important distinction from carbon; namely, the nature of the higher degree of oxidation. That is, silica (silicon dioxid, or silicic anhydrid), SiO2, is a solid, non-volatile and exceedingly infusible substance, very unlike carbon dioxid (carbonic anhydrid), CO2, which is a gas. This expresses the essential pecu- liarity of silicon. The cause of this distinction may be most probably sought for in the polymeric composition of silica compared with carbon dioxid. The molecule of carbon dioxid contains one atom of carbon and two atoms of 7 8 Chemical Notes. great quantity in the presence of each other in either kingdom, as the figures in the tables on the opposite page suggest. Silicon can- not replace carbon in the compounds which, under ordinary condi- tions, are functionally important in organisms. It may replace carbon in other organic compounds, however, such as chloroform. (Footnote.) General Nature of Carbon-Containing Compounds. 3. Carbon occurs not only in abundance in organisms, but is an important constituent of nearly all the solid substances in organisms. Practically all the substances which, under natural conditions, occur only in organisms are carbon compounds. Facts of special importance relating to the carbon-containing sub- stances are : 1. The very great multitude in which they occur. 2. The comparative complexity of their structure. 3. The relatively large number of atoms in the molecules of many of the compounds. 4. The comparatively great number of compounds that may con- tain the same kinds of atoms. 5. The marked instability or changeableness they usually mani- fest both in organisms and in the laboratory, under various con- ditions. Most of the leading carbon-containing compounds in organisms consist of carbon, oxygen, hydrogen and nitrogen. So varied/numer- oxygen, CO2, as is seen from the density of this gas. The molecular weight and vapor density of silica, were it volatile, would probably correspond with the formula SiO2, but it might be imagined that it would correspond to a far higher atomic weight, equivalent to SinOzn, principally from the fact that SiH4 is a gas like CH„ and SiCl4 is a liquid and volatile, boiling at 57° C. -that is, even lower than CC14, which boils at 76° C. In general, analogous compounds of silicon and carbon have nearly the same boiling points, if they are liquid and volatile. [Chloroform, CHC1S, boils at 61° C., and silicon chloroform, SiHCls, at 34° C.; silicon ethyl, Si(C2H5)4 boils at about 150° C. and its corresponding carbon com- pound, C(C2H5)4, at about 120° C.] From this it might be expected that silica, SiO2y would be a gas like carbon dioxid, CO2, whilst in reality silica is a hard non- volatile substance (at ordinary temperatures) and therefore it may with great cer- tainty be considered that in this condition silica is polymeric with SiOs, as on poly- merization (25) . . . very frequently gaseous or volatile substances change into solid, non-volatile, and physically denser and more complex substances." (108) [Mendelejeff.] Introduction. 9 II. Estimated Elementary Composition of a Man. Height, 5 Ft. 8 In.; Weight, 148 Lbs. [Moss.] Lbs. Per Cent. 1. Oxygen 92.40 ...62.291 83 60 2. Carbon 31.60 ...21.31 J 3. Hydrogen 14.60 9.84) 12 95) ■ 99.40 4. Nitrogen 4.60 3.11 j 15 80 5. Calcium 2.80 1.901 9 1 6. Phosphorus 1.40 0.95 j Z. oO J 7. Potassium 0.34 0.23 8. Sulfur 0.24 0.16 9. Chlorin 0.12 0.08 10. Sodium 0.12 0.08 0.60 11. Magnesium 0.04 0.02 12. Iron 0.02 0.01 13. Silicon 0.02 0.01 14. Fluorin 0.02 0.01 15. lodin 16. Manganese u 148.32 100.00 Notes, a. Trifling quantities of aluminium, arsenic, bromin, copper, lead, zinc and a few other elements, occur naturally in some organisms. b. The elements indicated by italics occur in organisms in much larger relative quantities than they do in the inorganic world. I. Estimated Percentage Elementary Composition of the Earth's Crust Including Water and Air. [Clarke.] 1. Oxygen 2. Silicon 3. Aluminium 7.26 ) ....49.981 ....25.30 ...12.34 ■75.28'1 4. Iron 5. Calcium 5.08 j 3.511 .22.85 . 99.07 6. Magnesium 2.50 -...10.51 7. Sodium 2.28 8. Potassium 9. Hydrogen 2.22 J ...0.94 ■ 10. Titanium 0.30 11. Carbon 0.21 12. Chlorin 0.15 13. Phosphorus 0.09 14. Manganese 0.07 ...0.92 15. Sulfur 0.04 16. Barium 0.03 17. Nitrogen 0.02 18. Chromium 0.01 19. Fiuorin, iodin, lead, copper, zinc, tin, mercury, arsenic, silver, gold, platinum and all others (combined) 0.01 100.00 Note. The elements indicated by italics are either entirely miss- ing from organisms, or occur at most in only very minute amounts. 10 Chemical Notes. ous and important are the biological and laboratory combinations in which these four elements unite - together and also with various additional elements, such as sulfur and phosphorus-that the carbon- containing compounds, as a class, have long been special objects of extended chemical study. Our knowledge of the carbon-containing compounds comprises one of the main branches of chemistry, called organic chemistry. The Original Distinction Between Inorganic Chemistry and Organic Chemistry. 4. Substances are commonly regarded, in a general way, as either organic or inorganic. The original division of substances into these two general classes was based upon an erroneous deduction. The earlier chemists noted the fact that organisms consist very largely of carbon-containing compounds. It was found by them that these carbon-containing substances could be converted readily, by ordi- nary laboratory means, into mineral products such as carbon dioxidj water, nitrates, ammonia, phosphates, sulfates, etc. It was also observed that these simple decomposition products were the sub- stances which plants removed from the soil or the air during their growth, and which were used by plants for the formation of their carbon-containing constituents. Many attempts were made in the laboratory to construct, from the above or similar analytic products, typical carbon-containing compounds found in plants or animals. All such efforts, through the agency of customary laboratory methods, were unavailing, however. Consequently, the invariable failure in the laboratory to pro- duce, from mineral products, such vegetable substances as starch, or such animal substances as uric acid, led chemists to assume that the carbon-containing substances in organisms possessed cer- tain qualities, aside from differences of composition, structure, etc., which distinguished them from all substances not made in organ- isms. It was observed, in this connection, that the carbon-contain- ing substances in organisms were formed naturally from mineral substances (directly or indirectly). It was believed, however, that these " organic " substances were formed, not merely by chemical and physical agencies, but as immediate results of the life process, i. e., of a supreme, directive, " vital force" inherent in organisms, Introduction. 11 but absent from the forms of the mineral kingdom. It was further concluded by the earlier chemists that on this account it would always be impossible to make artificially, by any method, the carbon- containing substances produced (in their day) only in organisms.* These, conclusions were universally accepted as correct. All substances that were produced only in organisms were accordingly termed organic substances, and formed the subjects of organic chem- istry. All other substances were called inorganic substances and became the subjects of inorganic chemistry. The latter branch of chemical science developed rapidly because synthesis of inorganic compounds from the elements, as well as analysis into the elements, could be readily effected and the structural characters of such com- pounds ascertained with relative ease. Organic chemistry, on the other hand, developed slowly, at first, because synthesis of organic compounds from the elements, and study of their constitution, seemed to be impossible. The First Production of an Organic Compound from an Inorganic Compound. 5. The view that the carbon containing substances in organisms could never be made by purely chemical means, and that their formation required the directive influence of a vital force, was overthrown in 1828. In that year Wohler made the first "or- ganic" compound from an "inorganic" compound. He found that when an aqueous solution of ammonium iso-cyanate was al- * "So early as at the close of the seventeenth century mineral substances were classed apart from vegetable and animal, the three being treated separately in text- books of chemistry. . . . This division was in accordance with the classification of natural substances according to the three 'kingdoms of nature,' which was even then in vogue. It was from this empirical standpoint that the chemistry of organic compounds developed itself, after Lavoisier had proved qualitatively that the main constituents of these were carbon, hydrogen, oxygen and sometimes nitrogen, occasionally together with sulfur and phosphorus. . . . The line which remained drawn between vegetable and animal substances was only gradually removed as the knowledge increased that the same chemical compounds occurred both in vegetables and animals, as was proved in the case of several fats, formic acid, benzoic acid, etc. Still it was generally felt to be necessary to strictly dis- tinguish organic from inorganic bodies, it being represented as an infallible dis- tinction that the former could not be prepared directly from their elements. But even this barrier was destined to fall before very long, and both classes of com- pounds to be regarded henceforth from the same standpoints." [Meyer.] 12 Chemical Notes. lowed to evaporate spontaneously, urea was formed by an isomeric (reversible) reaction, as follows : ,nh2 »=c< nh2 Urea O=C=N-NH4TXO: Ammonium iso-cyanate Ammonium iso-cyanate is an inorganic substance which does not occur in organisms.* Urea is the leading carbon-containing con- stituent of the urine and is present in small quantities in various parts of the animal body. Wohler's discovery removed the original distinction between inorganic and organic chemistry, for it demonstrated that a typical organic compound could be produced from inorganic matter by one of the simplest of laboratory methods, and entirely without the directive influence of any force associated with the life process. Since the time of Wohler's discovery there have been hundreds of syntheses, even from the elements, of carbon-containing com- pounds long thought to be peculiar to organisms (60). At present only a few types of carbon-containing constituents of organisms have resisted synthesis by artificial means. It is very probable, though by no means certain, that ultimately the artificial produc- tion of every organic substance may be effected. Thus, it is evident that the fundamental laws of organic chemistry and of inorganic chemistry are identical, and that the chemistry of the carbon-containing compounds is in principle the same as the chemistry of the compounds of silicon or of any so-called inorganic substances. Organic chemistry is not an independent chemical science, therefore, but merely an arbitrarily designated portion of * Before Wohler's discovery various organic compoundshad been made from other organic compounds. Thus "Scheele, as far back as 1776, had synthesized oxalic acid, hitherto only found in sorrel, from sugar and nitric acid ; Dobereiner, in 1822, had shown that tartaric acid on oxidation yields formic acid, which had been previously obtained by the distillation of ants with water." [Cohen.] In such cases it could not be said, however, that the organic products were derived from inorganic substances. They were merely derivatives of more complex organic products. At the time Wohler used ammonium iso-cyanate for the production of urea it was necessary to take organic matter for the synthesis of the CN radical and the subsequent preparation of a cyanate, but as the CN radical was formed by ignition of the dry organic mass with a carbonate, i. e., by conversion of the organic matter to inorganic, the ultimate production of urea was effected from a typical "in- organic" compound. Introduction. 13 general chemistry. The general distinction between organic chem- istry and inorganic chemistry has been retained merely for reasons of convenience. Organic Chemistry is the Chemistry of the Hydro- carbons and Their Derivatives. 6. Organic chemistry is frequently designated the " chemistry of the compounds of carbon." A few carbon compounds, however, such as the common carbonates, carbon dioxid, cyanogen, cyanids, cyanates, etc., are more conveniently classified as inorganic products, although carbon dioxid is intimately connected in one way or another with the life process in all organisms. In view of these exceptions organic chemistry may be more definitely termed the chemistry of the hydrocarbons (13) and their derivatives.* Such carbon-con- taining compounds will engage our attention during the remainder of the course and will furnish the subject matter of these notes. The General Principles of Organic and Inorganic Chemistry are Identical. 7. General facts. From what has already been said regarding the sameness of the principles underlying inorganic and organic chemistry, it follows that many chemical facts may be illustrated as well by the carbon-containing compounds as by members of the inorganic class of substances. The general facts we have already learned regarding molecules, atoms, electrons, chemical affinity, reactions, chemical change, heat and chemical change, osmosis, electrolysis,! and so on, apply with equal force to the organic com- pounds as a class. 8. Radicals. There are no elementary substances peculiar to or- ganic chemistry. All the elements met with in organic compounds, * A hydrocarbon is a substance containing only hydrogen and carbon, such as methane, CH4 (60). The term hydrocarbon should be carefully distinguished from carbohydrate. A carbohydrate is an organic substance containing carbon, hydrogen and oxygen. Sugar is a carbohydrate. The hydrogen and oxygen atoms of a car- bohydrate are usually present in its molecule in the proportion in which they are contained in the water molecule. Thus, glucose is a typical carbohydrate, with the empirical formula, C6H12O6. This formula might be written empirically (C - H2O)6 to suggest that glucose is a carbo{x^hydrate. We shall see later on, however, that such a formula would hide important facts in this connection. f Most organic compounds are non-electrolytes (39). 14 Chemical Notes. chiefly carbon, oxygen, hydrogen, nitrogen, sulfur and phosphorus, occur in inorganic compounds and have been considered in our study of inorganic chemistry. Each of the substances dealt with in organic chemistry is a compound containing one or more carbon atoms and at least two additional non-carbon atoms. The chief differ- ences among the organic compounds are due to variations in molecu- lar composition or structure, or both. All organic compounds con- tain one or more radicals. Most organic compounds contain at least two radicals. As a rule structural variations among organic compounds are dependent upon differences in the kinds and mutual relationships of the constituent radicals. Consequently radicals are subjects of constant inquiry in organic chemistry. 9. Notation and Nomenclature. The system of notation for organic compounds is in general the same as that used in inorganic chemistry. As a rule the formulas of substances are written in constitutional arrangement because of the need of indicating radicals. Empirical formulas are of little significance. Nomenclature, as might be expected, is necessarily different. Names of organic sub- stances are largely determined by the names of the radicals contained in the compounds. Many of the common names of organic sub- stances are without such significance, however. The complexity of the organic compounds accounts for the great variety of names em- ployed to designate them. Nomenclature will be considered as we proceed with our consideration of the different groups of substances to be reviewed. Sources of the Carbon-containing Compounds. 10. Besides a few carbon-containing substances of mineral char- acter, such as carbonates (6), the chief sources of typical organic compounds are the following: Biological. 1. Plants. Albuminous substances, albumins and globulins especially ; fats and oils; sugars, starches and celluloses; alkaloids; salts of various acids, such as oxalic acid, tartaric acid, citric acid, etc. 2. Animals. Albuminous substances: besides albumins and globulins, also hemoglobin, collagen, keratin, etc.; fats and oils; " animal starch" (glycogen); "animal alkaloids" (ptomains) ; urea, uric acid, etc. Introduction. 15 3. Microorganisms. Products of fermentation and putrefaction, such as alcohol, acetic acid, lactic acid, marsh gas, skatol, ptomains, etc. Subterranean (fossiliferous - ?) mixtures such as natural gas, petroleum and coal, the main sources of the hydrocarbons (54). Artificial. Numerous compounds and mixtures, produced in the laboratory from various compounds and mixtures derived from the above sources or from the elements, such as coal tar, bone oil, chloroform, ether, acetylene, iodoform, phenyl hydrazin, etc. Explanation of the Cause of the Great Number and Variety of the Carbon-containing Compounds. II. We have already noted, and the above statement of sources indicates, that the varieties of carbon-containing compounds are very numerous. These compounds also vary in structure and com- position, from simple forms containing only a few atoms of two kinds, such as acetylene, C2H2, to complex forms containing a total of a thousand or more atoms of a half-dozen kinds, such as hemo- globin, C63SH1025N164FeS3O181. The number and the great variations in structure of the carbon- containing compounds depend upon the fact that carbon atoms, which are tetra-valent, possess the property of attracting and holding one another, with one or more of their valences, while each retains its attraction for other atoms with all of its remaining valences. Thus, the carbon atoms, by holding together tenaciously, form nuclei of variable size and character, around which atoms of other kinds may be collected in a number determined by the valences of such non-carbon atoms and by the sum of the valences not satisfied by the attractions between the carbon atoms themselves. One of the simplest carbon-containing compounds is the hydro- carbon known as marsh gas or methane. It is formed in marshes during the decay of vegetable matter, is a conspicuous constituent of natural gas, and is formed in the intestine in small quantity, as a result of fermentation of undigested carbohydrates and of the putre- faction of albuminous substances. Methane consists of one carbon atom and four hydrogen atoms, and its empirical formula is CH4(60). Methane may be readily converted into a related hydrocarbon called ethane, C2H6. Propane, C3H8, may be formed, directly or 16 Chemical Notes. indirectly, from each of the two preceding compounds. Butane, C4H10, may be formed directly or indirectly from each of the three preceding compounds. Pentane, C5H12, and hexane, C6H14, may be derived in similar manner. The mutual relations of these six typical organic compounds are shown by their structural formulas, given below, which also illus- trate our previous remarks on the fact that carbon atoms unite with one another to form molecular nuclei of variable size and character. Homology. 12. The six hydrocarbons whose formulas are indicated above are obviously closely related. The fact that the second, third, fourth, fifth and sixth hydrocarbons may be produced directly or indirectly from any of the preceding substances in the series, as named, is presumptive evidence of such a relation. This close rela- tion of the compounds is also suggested by the formulas, which show certain regular mathematical differences as follows : Hydrocarbon. Relation to the formula of methane. Relation to the formula of the preceding compound in the series. Name. Methane Formula. ..ch4 Ethane -c2h6 CH4 + CH2 CH, +CH2 Propane ..C3H8 CH4+(CH2)2 c2h6 +ch2 Butane •AH10 CH4 + (CH2)S c3H8 +CH2 Pentane ..C5H12 CH4+(CH2)4 C,H10 + CH2 Hexane -c6Hu CH4+(CH2)5 Thus it is evident that between any two consecutive hydrocarbons, in the series under consideration, there is the same difference of one carbon atom and two hydrogen atoms, i. e., CH2. Such a rela- tion between substances is known as homology. Such a series as Introduction. 17 the one indicated above is therefore called a homologous series.* Each member of a homologous series is a homologue of the series. Most organic substances are members of homologous series. That the homologous series indicated by the above formulas is a natural series may be inferred from the fact that the formula of each member of the series can be correctly represented by the gen- eral formula, CnH2n+2, in which n represents the number of the carbon atoms in each compound. Thus, for CHp n - 1 and the formula may be written C.H,, „; for C„H„, n = 2 and the formula may be written C2H2X2+2; and so on. Hydrocarbon Series. 13. The hydrocarbons referred to on page 16 are the simplest members of the paraffin series. There are many more members of that particular series (50), just as there are additional series of en- tirely different hydrocarbons. The difference between the formulas of any two consecutive members in each hydrocarbon series is always CH2. All purely organic substances are either hydrocarbons or their derivatives, just as all substances are either elements or their combinations. The hydrocarbons are the primary organic com- pounds. The names, formulas and simplest representatives of the main series of hydrocarbons are given on page 18. A glance at the for- mulas of the simplest members of each of these series shows that the proportion of hydrogen decreases and the proportion of carbon increases from the simplest series (QH2zi+2) to the most complex (CnH2n_40). Some hydrocarbons have not yet been located in a particular series, presumably because their immediate relatives have not yet been found. Hydrocarbons of Biological Importance. 14. With the exception of methane of the paraffin series, none of the free hydrocarbons occurs naturally in animals. The terpenes are the only free hydrocarbons that occur conspicuously in plants. The organic compounds of greatest biological importance are various derivatives of the hydrocarbons. By far the most important *Such a series is analogous to the oxid of nitrogen series (N2O, N2O2, N2O3, N2O4, N2O-), in which the proportion of oxygen increases regularly from the low- est to the highest member, i. e., there is a regular increase in molecular complexity. 18 Chemical Notes. organic compounds in animals and plants are derivatives of the paraffin or of the benzene series. Many of the most conspicuous biological substances are combined derivatives of both these series of hydrocarbons. Hydrocarbon Series.* Name of Series. General Formula. Simplest Member Known.f Formula of Simplest Member. Paraffin C,iH2?1+2 Methane ch4 OlefinJ CnEGn Ethylene C2 H4 Acetylene^ On-tOn-2 Acetylene c2 h2 ValyleneJ Cn±±2n-4 Valylene C5 H6 BenzeneJ GnH2n-6 Benzene Co Styrene CnH2n-8 Styrene c8 H8 Phenyl acetylene Cnli2n-10 Phenyl acetylene C8 H6 Naphthalene CnH2n-12 Naphthalene c10h8 Bi-phenyl Stilbene OnH 2n-14 C?iH2n-16 Bi-phenyl Acenaphthylene C^Hjo c12h8 Anthracene 0nH2w-18 Anthracene CuH10 Benzyl naphthalene CmH2n-20 Fluoranthene c15h10 Pyrene 0nH2n-22 Pyrene CigH10 Chrysene 0nll2n-24 Chrysene Ci8H12 Bi-naphthyl CnH.2n-26 Bi-naphthyl C2oliu Di-naphthyl ethylene CnH2n-28 Di-naphthyl ethylene C22 H16 Picen 0nll2n-30 Picen C22H14 Tetra-phenyl ethylene.... 0nH2n-32 Di-naphthyl anthrylene.. C22D12 Di-naphthyl di-acetylene.. Cn-H.2n-34 Di-naphthyl di-acetylene CMHU Di-bi-phenylene ethene... 1^/4112/1-36 Di-bi-phenylene ethene.. C26-^16 Bi-anthryl CnU2n-38 Bi-anthryl C28H18 Carbopetroceng On-tOn-40 Carbopetrocen C24H8 Terpene (C5H8)a Terpene CiqHjg General Classification of Organic Compounds. 15. General principle of classification of the compounds of carbon. " In considering the elements and compounds included under the head of inorganic chemistry, the fundamental substances are, of course, the elements. The properties of the elements enable us to separate them, for study, into a number of groups; as, for example, the chlorin group, including bromin, iodin, and fluorin; the oxygen group, in which are included sulfur, selenium, and tel- lurium. To recall the method generally adopted, we may take the *The student is not expected to memorize any of the names or formulas in this particular table. The more important series of hydrocarbons will be consid- ered in some detail farther on. t In the higher, i. e., more complex, series, there are usually several isomeric (24) substances having the simplest formula. t There is at least one additional series with the same general formula. § The series CnH2?i-4o is not the highest. Thus, there is a hydrocarbon with the formula C50H46 (CnH2n-54). Introduction. 19 chlorin group. In studying the members of this group, there is found great similarity in their properties. Their hydrogen com- pounds next present themselves, and here the same similarity is met with. Then, in turn, the oxygen and the oxygen and hydro- gen compounds are considered, and again the resemblances in prop- erties between the corresponding compounds of chlorin, bromin, and iodin are met with. We thus have groups of elements, and of the derivatives of these elements : as, Cl Br I C1H BrH IH C1O3H BrO3H IO3H, etc. Of course, the chlorin group is quite distinct from the oxygen group and from all other groups ; and each member of the chlorin group is, at least so far as we know, quite independent of the other mem- bers. We cannot make a bromin compound from a chlorin com- pound, or a chlorin compound from a bromin compound, without directly replacing the one element by the other. " Now, when we come to study the compounds of carbon, we shall find that the same general principle of classification is made use of; only, in consequence of the peculiarities of the compounds, the system can be carried out much more perfectly; the members of the same group can be transformed one into the other, and it is also possible to pass from one group to another by means of com- paratively simple reactions. " The simplest compounds of carbon are those which contain only hydrogen and carbon, or the hydrocarbons. All the other com- pounds may be regarded as derivatives of the hydrocarbons. As we have seen, there are several groups or series of hydrocarbons (13). These correspond somewhat to the different groups of elements. The members of one and the same series of hydrocarbons resemble one another more closely than the members of one and the same series of elements. Although we have indications of the existence of more than twenty-five series of these hydrocarbons, only three or four of the series are at all well known. . . . " Starting with any series of hydrocarbons, several classes of derivatives can be obtained by treating the fundamental compounds 20 Chemical Notes. with different reagents. The chief classes of these derivatives are: (1) those containing halogens; (2) those containing oxygen, among which are the alcohols, ethers, acids, etc.; (3) those containing sulfur ; and (4) those containing nitrogen. Corresponding to every hydro- carbon, then, we may expect to find representatives of these differ- ent classes of derivatives. But the relations existing between any hydrocarbon and its derivatives are the same as those existing between any other hydrocarbon and its derivatives. Hence, if we know what derivatives one hydrocarbon can yield, we know what derivatives we may expect to find in the case of every other hydrocarbon. The student who, for the first time, undertakes the study of carbon chemistry, is very apt to feel overwhelmed by the enormous number of compounds described in the book or by the lecturer. This large number is really not a serious matter. No one is expected to become acquainted with every compound. A great many of these need only be referred to for the purpose of in- dicating the extent to which the series to which they belong have been developed. In general, the members of any series so closely resemble one another, that, if we understand the simpler members, ice have a fair knowledge of the more complicated members." [Remsen.] 16. Main groups of organic compounds. The great number of organic substances may be arranged in three main divisions, as follows: 1. Fatty compounds. 2. Carbocyclic compounds. 3. Heterocyclic compounds. In the first group the carbon atoms are in chain-like arrrange- ment. In the second and third groups the carbon atoms are in ring- like formation. Thus: Chain-like formation : 11 Open chain." Introduction. 21 Ring-like formation* : "Closed chain." 17. Fatty compounds. This group of organic compounds is given the name " fatty " because the animal and vegetable fats belong to it. The fats were among the first members of the divi- sion to receive special study. The fatty compounds are also called the aliphatic substances, methane or marsh gas derivatives, chain-like or acyclic carbon com- pounds. All of these terms are synonymous. All of the fatty substances may be obtained from methane, CHi (50). The carbon atoms in them are in chain-like formation. The fatty substances may be subdivided into (1) Saturated compounds, (2) Unsaturated compounds. The saturated fatty compounds are the parafin hydrocarbons and their derivatives. In the paraffins the carbon atoms in direct union are linked to one another by single bonds, three valences of each carbon atom being " satisfied " by non-carbon atoms or certain radicals, or both. Consequently, in paraffin compounds containing two or more carbon atoms, the total number of carbon affinities which is satisfied or saturated by non- carbon atoms or various radi- cals, or both, equals twice the number of carbon atoms in the chain, plus 2, i. e., 2n -}- 2 (12). The general formula of the paraffin de- rivatives is CnX2n + 2, in which X represents the valences of atoms or radicals, or both, united directly to the carbon atoms in the chain (12). The unsaturated fatty compounds may result from the saturated sub- stances when at least two carbon atoms lose an even number of affini- ties for non-carbon atoms, or for radicals, or for both, and when there is a corresponding gain of bonds between the same carbon atoms * Few elements except carbon form such rings, chief among them being nitro- gen, oxygen and sulphur (18). Allotropes are probably iso-cyclic, as in the case of ozone, 22 Chemical Notes. in the chain. Such compounds are unsaturated in the sense that multiple bonds between pairs of carbon atoms in the chain can be diminished uniformly to single bonds, and the number of valences of each carbon atom in the chain for non-carbon atoms or for radi- cals, or both, can be restored to the maximum, three, and can be fully satisfied, i. e., the unsaturated fatty compounds can be con- verted into saturated fatty compounds. According to the number of affinities of the carbon atoms for non-carbon equivalents which are lost, but which may be returned when the compound is converted into a saturated substance, the general formulas are as follows, of which only the two most im- portant examples are indicated (20): 1. Compounds with two affinities capable of saturation, such as ethylene, C,X2h, (the simplest member of the olefin series of hydrocarbons. See page 18). 2. Compounds with four affinities capable of saturation, such as acetylene, CnX2n_2, (the simplest member of the acetylene series. See page 18). 18. Carbocyclic compounds. These compounds consist of rings of carbon atoms with free valences for non-carbon atoms, or for radicals, or for both. The most important of these belong to the benzene series of hydrocarbons and their derivatives, of which the simplest member is benzene, C6H6, with the following constitu- tional formula : The benzene compounds comprise the largest group of organic sub- stances. They are also known as the aromatic compounds. The Introduction. 23 latter name was applied because of the fact that many of the first known compounds of this class had an agreeable aroma.* 19. Heterocylic compounds, like the carbocyclic compounds, are ring compounds. In the carbocyclic substances, however, the rings consist solely of carbon atoms, whereas the rings of the heterocyclic substances contain non-carbon atoms, especially nitro- gen, oxygen or sulphur, associated with the carbon atoms. The non-carbon atoms in such rings are termed the hetero-atoms. The following constitutional formulas illustrate different heterocyclic types : *A few carbocyclic compounds represent transition products between the aliphatic and the aromatic compounds, such as : CHAPTER I. GENERAL CHEMICAL CONSTITUTION OF ORGANIC SUBSTANCES. The Valence and Combinations of the Carbon Atom. 20. Valence. The following facts regarding the structure of molecules of organic compounds are of fundamental importance : 1. The carbon atom is tetra-valent* (11). A carbon atom combines at most with only four uni-valent atoms or radicals, or with the equivalents of four such uni-valent affinities. Examples : ch4 Methane cf4 . Carbon tetra-fluorid. CCh Carbon tetra-chlorid. co2 Carbon di-oxid. cs2 Carbon di-sulfid. CH3-OH Methyl alcohol. chs-nh2 Methyl amin. CHC13 Chloro- form. 2. The four carbon valences are of the same nature and are equal to each other. One of the simplest of the organic substances is methane, CH4 (50). All of the hydrogen atoms of methane may be replaced by chlorin atoms. Thus, mono-chlor methane, CH3C1, may be made by substituting one chlorin atom for one hydrogen atom. If the carbon valences were different in any degree, more than one kind of mono-chlor methane might be producible. But only one kind of mono-chlor methane can be made. It is immaterial which hydro- gen atom is replaced by a chlorin atom, the mono-chlor methane is always the same. This is true, also, of the di-chlor (CH2C1,), tri-chlor (CHC13) and tetra-chlor (CC1J derivatives (65). Conse- quently, the carbon valences are the same in character. 3. Carbon atoms can unite with one another to form chains or rings (16). The union of a pair of carbon atoms, in an organic compound, may occur in one of three ways, as follows : (a) The two carbon atoms may be linked together by a single bond, in the molecular nucleus =C-C= having six free valences. This is the nature of the carbon linkage in the saturated compounds, such as the parafins (13). * In carbon mon-oxid, CO, carbon appears to be di-valent. 24 Chemical Constitution of Organic Substances. 25 (6) The two carbon atoms may be linked together by a double bond, in the molecular nucleus =C=C= having four free valences. This is the nature of the carbon linkage in some of the unsaturated compounds, such as the olefins (13). (c) The two carbon atoms may be linked together by a triple bond, in the molecular nucleus -C = C- having two free valences. This is the nature of the carbon linkage in some of the unsaturated compounds, such as the acetylenes (13). (d) The above facts are true of the carbon linkage in carbon chains, as the following simple illustrations indicate: Saturated [Paraffin] Propane * chain : Unsaturated [Olefin] Propylene * chain : Unsaturated [Acetylene] Methyl acetylene* chain: =C-C=C- (e) In carbon rings the bonds may be single or double, or both, as is shown in the following examples : Triple bonds do not occur between ring carbons. 21. Combinations. Saturated and unsaturated compounds. In saturated compounds the carbon atoms are linked together by single bonds, as indicated in the following formula (17) : Hexane, CH,-CH2-CH2-CH2-CH2-CH„ ' O A A A O The atoms or radicals attached to the chain or ring of such com- pounds cannot be increased in number without severing the chain or ring, and thus producing at least two new products. In short, direct addition f of atoms or radicals to saturated compounds is impossible (57). * The third member of the hydrocarbon series named, in parenthesis, on the same line. t See references to substitution, section 57. 26 Chemical, Notes. In unsaturated compounds, at least one pair of adjacent carbon atoms is linked together by double or triple bonds, as in the follow- ing examples (17) : Unsymmetric allylene,* CH3-C=CH [C3H4] Symmetric allylene, CH2=C-CH9 QC3EI4] When such double or triple bonds are decreased by chemical means to single bonds, saturated compounds may result without a rupture of the carbon chain or ring. These facts are illustrated by the following progressive reaction, in which a triple bond is changed to a double bond and the latter to a single link, in the ultimate transformation of an unsaturated compound into a saturated one. 22. Radicals are collections of atoms which remain together in various reactions and which may pass unaltered, like atoms, from one compound to another (23). Radicals cannot exist alone nor are they equivalent to molecules. They are merely groups of atoms which act en masse during chemical changes. The radicals in or- ganic compounds may contain many atoms. The arrangement of the atoms in the radicals is frequently very complex. Most radicals in organic compounds contain carbon atoms. By the successive removal of hydrogen atoms, one after another, from methane, CH., three different radicals with three different valences result, as follows : Combinations. Under favorable conditions, radicals can unite unchanged to form new molecules, as may be seen from the follow- ing typical reactions : * These substances are typical isomers (24). Chemical. Constitution of Organic Substances. 27 In some reactions radicals may change their size and character, either by subtraction or addition, to unite in the formation of new molecules, as the following examples indicate : 23. Homology (12). The members of a homologous series may be formed by a union of carbon-containing radicals, as follows : The linking qualities of the carbon atoms account for the fact of homology and explain the extraordinary number of carbon com- pounds (11). 28 Chemical Notes. 24. Nature. Chemists believed for many years that substances of different chemical and physical properties were necessarily different in chemical composition. So firmly fixed had this idea become that, when Liebig, in 1823, found that silver fulminate (CNOAg) and silver cyanate (OCNAg) had the same composition, his conclusion was generally supposed to be erroneous. Liebig's results were soon confirmed, however, and it thus became evident that substances of very unlike properties may have the same qualitative and quantitative composition. This fundamental fact was explained by assuming that the constituent atoms were differently combined in the molecule.* This assumption has been verified. The following constitutional formulas of the above compounds indicate the known structural dif- ferences between them: Isomerism. Silver fulminate, C=N-O-Ag Silver cyanate, O=C=N-Ag Many similar instances have since been discovered. Thus, the same fact is demonstrated by the constitutional formulas of two substances having the empirical formula C2H4C12. One of these may be made by treating ethane with chlorin and is called ethyl- idene chlorid. The other may be made by subjecting ethylene to the same treatment and is known as ethylene chlorid. Their struc- tural differences are seen at a glance below : All such substances, of dissimilar properties but of identical per- centage composition, are isomeric. Isomerism is of frequent occur- rence. In many instances more than two different substances con- tain the same kinds of atoms in exactly the same proportions. Each substance of such a group is an isomer of the others.f * The isomeric transformation of ammonium iso-cyanate into urea was also an instance of similar character (5). t Instances of inorganic isomerism are usually termed instances of allotropy (see inorganic "Notes," p. 83). Isomerism, metamerism and polymerism may be re- garded as varieties of allotropy. Allotropy applies to elements, isomerism to compounds. Chemical Constitution of Organic Substances. 29 Isomerism, like homology, is possible because of the chain or ring forming tendencies of the carbon atoms. The number of pos- sible isomers increases with .the accumulation of carbon atoms. The larger the molecule the greater the possible number of isomers of it. In the following summary there is indicated, for example, the greatest possible number of different arrangements of the atoms in the molecules of each of several of the simplest hydrocarbons of the paraffin series : Methane, CH4 1 Ethane, C2H6 1 Propane, C3H8 1 Butane, C4HW 2 Pentane, C5H12 3 Hexane, C6HU 5 Heptane, C7H16 9 Octane, C8H18 18 Nonane, C9H20 35 Decane, C10H22 75 Undecane, CUH24 159 Dodecane, C12H26 354 Tridecane, C13H28 802 From the figures above, it is evident that there are two butane isomers, three pentane isomers, and so on.* 25. Kinds. Isomerism varies in kinds with differences in the (1) molecular masses, in the (2) intra-molecular structures, and in the (3) molecular shapes of isomers. Accordingly, we find (1) meta- meric and polymeric isomers, and also recognize (2) chain isomerism, isomerism of position, and (3) stereo-isomerism (optical and geometric). Metamerism. Isomers may have the same molecular roeights, i. e., their molecules may contain the same numbers of the same kinds of atoms. Such substances are metameric. Thus there are metameric butanes, as follows : Normal butane, CH„-CH2-CH2-CH. [C4HJ * O Z L O I- 4 IvJ Iso-butane, CH,-CH^ rcn i ' 3 \CH, L 4 10J Polymerism. Isomers may have different molecular weights, i. e., their molecules may contain different numbers (common multiples) of the same kinds of atoms. Such substances are polymeric, of which the following are typical examples: Acetylene, C2H2 Benzene, CAL Styrene, CSH8 * Although only a few of the indicated isomers are known, there is excellent reason for believing that all of them could be prepared (64). Benzene and styrene are polymers of acetylene. 30 Chemical Notes. 26. Nucleus or chain isomerism. In our discussion of homol- ogy (12) it was shown that ethane may be made from methane by a very simple reaction ; also that higher members of the same series of compounds may be made in a similar manner. The methods of preparation alluded to make it obvious that ethane may be regarded as a substitution product of methane, i. e., as methane with one of the hydrogen atoms of the latter replaced by the methyl (CH3) radical, or as two methyl radicals united together as follows : From the same standpoint propane may be considered a similar substitution product of ethane : A study of the constitutional formulas of these three substances makes it evident that at least one carbon atom is in a new inter- atomic relation in each successive compound. In methane the solitary carbon atom is united only to hydrogen atoms. In ethane each carbon atom is united to three hydrogen atoms and to one carbon atom. In methane each hydrogen atom bears apparently the same relation to the single carbon atom. In ethane the hydrogen atoms bear the same relation to the pair of carbon atoms or to the single carbon atom with which each is directly united. In methane we have only a central carbon atom, in ethane only two terminal carbon atoms. It is obvious, therefore, that, if we substi- tute a single mono-valent atom or radical, such as chlorin or methyl, CH3, for a hydrogen atom in either methane or ethane, the product would be the same for each compound, no matter which hydrogen atom should happen to be displaced (20). Chemical Constitution of Organic Substances. 31 In the case of propane a carbon atom is in still a different position. In propane we distinguish two terminal carbon atoms and an inter- mediate (central) carbon atom. Each terminal carbon atom, and each of the hydrogen atoms attached to it, bears the same relation to its immediate neighbors as it does in ethane. The central carbon atom, however, is linked to two carbon atoms and to only two hydrogen atoms. Consequently, if we substitute a single mono-valent atom or radical, such as chlorin or methyl, CH3, for a hydrogen atom in propane, the. substitution product would be of one type if any one of the six terminal hydrogens were displaced, but would be of a different nature if one of the two intermediate hydrogens were dis- placed. This may be seen in the following formulas, which show the relations between propane and the two butane isomers : ch3-ch3-ch2-ch3 [C4H1o] The normal butane may be produced from propane by substi- tuting a methyl radical, CH3, for any one of the six terminal pro- pane hydrogens. The iso-butane, on the other hand, results from a similar substitution of one of the two intermediate hydrogens. The normal butane has a continuous carbon chain, the iso-butane has a branched carbon chain. The butanes are metameric isomers. Although they have exactly the same composition, their physical and chemical properties, like their internal structures are very different. The number of possible isomers increases with the number of carbon atoms in the chain (24). Isomerism of the kind just illustrated is due to differences in the structure of the carbon chain and, therefore, is designated nucleus or chain isomerism. 32 Chemical Notes. 27. Isomerism of place or position. Since all the hydrogen atoms in methane bear the same relation to the carbon atom, it is obvious that if any single hydrogen atom is substituted by another mono-valent atom or radical, but one mono-substitution product can be produced by any one of the substitutes. Thus there can be but one mono-chlor methane, CH3 - Cl. For the same reason there can be but one mono-chlor ethane, C2H5 - CL In the case of propane, and the higher homologues of the series of which it is a member, the facts are different. We have already seen that propane yields two kinds of mono-methyl propanes, i. e., normal and iso-butanes (26). Propane likewise forms two varieties of any kind of mono- substitution products, for similar reasons. Thus, there are two mono-chlor propanes, as follows : CH3-CH2-CH2C1 Normal propyl chlorid CH3-CHC1-CH3 Iso-propyl chlorid In isomeric compounds of this type the carbon chain is unaffected, but the positions of the substituted atoms or radicals are different. For this reason such isomerism is designated isomerism, of place or position. There are many such metameric isomers. 28. Stereo-isomerism. Every molecule, like every mass, has extension in three directions. The atoms of a molecule are doubt- less constantly in motion, but instead of being in a state of confused movement, they appear to rotate periodically about certain points in fixed relations to each other, i. e., they are in a condition of " internal stability." All constitutional formulas may be regarded as " expressions of the positions of certain points about which the atomic motion, doubtless a periodical motion, takes place." [Van't Hoff.] " The valence of an atom or radical represents not only its power of combining with other atoms or radicals, but is the resultant off forces which regulate the position in space (in the molecule') of that atom or radical. In the cases of atoms or radicals of more than one valence, these forces are directed in space in definite directions, which may be changed, however, by one con- dition or another. In the cases of unsaturated compounds, these forces or linkings may be double or multiple." [Hantzsch.] Constitutional formulas, although commonly constructed in planes, imply spatial relationships of the molecular parts. There are Chemical Constitution of Organic Substances. 33 numerous isomers of shape-isomers in which the molecular con- figurations, i. e., spatial relations of the molecular parts, are dif- ferent, although the chemical relations of the molecular parts are identical. Such physical isomers illustrate stereo-isomerism. Stereo- isomerism is also designated stereo-chemical isomerism.* " Stereo-chemical isomers identical in the mode of union of the atoms, one to another, differ only in the geometric relations of the atoms composing the compound. It is indeed difficult to formulate any characteristic distinctions, but one may say that usually they differ from constitutional isomers, in that they are transformed more easily one into the other. This should tend to prove that the geometric positions of atoms in a molecule can be much more easily changed than the respective linkings. " Stereo-isomers may be subdivided into two classes : " 1. Substances identical in all their principal properties, but which produce different effects on polarized light; in other words, which are characterized by differences in optical activity. These are called optical isomers. In these compounds one may regard the atoms as placed at the same absolute distances from each other, but disposed in different orders. . . . " 2. Substances which are without action on polarized light, but which, in spite of the identity of their constitutional (plane) formulas and the characteristics which result therefrom, present differences in their chemical and physical behaviors which cannot be explained by simple formulas. These substances occur in the groups of cyclic compounds, and also among the unsaturated com- pounds or in those containing double bonds. For lack of a more precise term compounds of this class are called geometric isomers. With respect to these isomers it is assumed by the stereo-chemist that the distances between the atoms are different." [Hantzsch.] 29. Optical isomers may be of three kinds : dextro-rotary, levo- rotary, inactive f Thus, for example, there are eight possible con- * Stereo-chemistry is that branch of chemistry which treats particularly of the relations between the chemical and physical properties of substances and the con- figurations of their molecules. f Optical isomers are substances which, when in liquid condition (fused or dis- solved), turn the plane of polarized light to the right or left. Compounds of this kind are said to be "optically active." The substances that turn the plane of polarized light to the right are called ' ' dextro ' ' rotary ; those that turn it to the 34 Chemical Notes. stitutional isomers of the group of alcohols containing five carbon atoms, all of which are known and are termed collectively, amyl alcohols, C5H12O.* One of these isomers, secondary butyl carbinol, exists in three different geometric forms, although thep/ane constitu- tional formula of each is the same and may be written as follows : f " The three secondary butyl carbinols with this constitution have identical chemical properties; their physical constants are also almost all the same, but one of the latter serves to distinguish them from one another. When a beam of plane polarized light is passed through layers of these three alcohols, the plane of polariza- tion is rotated by one isomer to the left, by another to the right, while the third produces no rotation. The first two are said to be optically active. " Since the differences between optically active compounds depend only upon physical constants, while their chemical properties are identical, it may be asked whether these differences are not purely physical ones, arising from differences in the arrangement of the left are termed "levo" rotary. Dextro-rotation is usually indicated by a + sign or an italic d- before the name of the substance ; levo-rotation is indicated by a - sign or an italic I- in the same position. Most organic substances, like most inorganic compounds, are without influence on the plane of polarized light and are, therefore, said to be " optically inactive." * The eight metameric amyl alcohols have the following plane constitutional formulas (75) : 1. Normal primary amyl alcohol CH3-(CH2)3- CH2OH. 2. Iso-butyl carbinol (76) (CH3)2 = CH - CH2 - CH2OH. 3. Secondary butyl carbinol CHS - *CH(C2H5)-CH2OH. 4. Methyl propyl carbinol CH3-(CH2)2 - *CHOH-CH3. 5. Methyl iso-propyl carbinol (CH3 )2 = CH - * CHOH - CH3. 6. Di-ethyl carbinol C2H5 - CHOH - C2H5. 7. Di-methyl ethyl carbinol (CH3)2 = C(OH) -C2H5. 8. Tertiary butyl carbinol (CH3)S = C - CH2OH. f Three of the eight amyl alcohols (3, 4, 5 above) contain a carbon atom united to four different atoms or radicals. Each of the carbon atoms referred to is indicated in the above formulas by a star and is called an ' ' asymmetric ' ' carbon atom (see page 36). Each of the alcohols containing an asymmetric carbon atom may occur in three isomers of shape, two of which are optically active and one is optically inactive. Consequently, amyl alcohol exists in a total of fourteen isomeric forms. Similar facts are true of many organic substances. Chemical Constitution of Organic Substances. 35 molecules, such as are supposed to exist in the case of dimorphous substances. * There are two reasons opposed to this view. First, differences in the arrangements of the molecules can only be sup- posed to exist in the case of solid substances, because it is only in these that the molecules have a fixed position in relation to one another, f The molecules of liquids and gases are free to move independently; but they, too, afford examples of optical activity. In the case of liquids there is still a possibility that not the molecules themselves but conglomerations of them, arranged in a definite manner, may be free to move. Were this the cause of optical activity, optically active liquids when converted into the gaseous state should, their vapor densities being normal, produce no rotation of the plane of polarization. That they actually do produce this rotation was proved by Biot, and later by Gernez. In this case, therefore, the phenom- enon cannot be attributed to differences in the arrangement of the molecules, because in a vapor of normal density each molecule is capable of independent motion. Second, the optical activity shows itself in derivatives of optically active substances. Hence it follows that an explanation of the rotation of the plane of polarization in the case of liquids and of dissolved substances must be sought for in the structure of the molecules themselves. "The question now arises as to what peculiarity of the structure of the molecules is the cause of this phenomenon. The following considerations will show how an insight may be obtained into it. Levo-rotary amyl alcohol, the plane constitution of which was indi- cated on the opposite page, is converted by the action of gaseous hydriodic acid (HI) into amyl iodid, with the constitution * A dimorphous substance is one which has the property of assuming two distinct forms. Some elements and many substances crystallize in two different forms under different conditions. These effects are due to different arrangements of the molecules in the crystalline masses (footnote, page 37). f Each of the amyl alcohols is a liquid. 36 Chemical Notes. This compound is optically active. By treating it with nascent hydrogen, the iodin atom is replaced by hydrogen, with formation of a pentane, This compound is optically inactive. But if the amyl iodid (2) is subjected, instead, to the action of ethyl iodid in the presence of sodium, there results a heptane, and this substance is optically active. " An examination of these three optically active substances (1, 2, 4) shows that they differ from optically inactive pentane in the following way: In the latter there are two similar groups (methyl, CH3) linked to the central carbon atom, whereas in the others (all optically active}, the four groups linked to the central car- bon atom are all different.* li Van't Hoff has shown that optically active compounds in general contain at least one carbon atom linked to four different atoms or radicals ; and he has designated a carbon atom linked in this way, an asymmetric carbon atom." [Holleman.] Saturated compounds containing one asymmetric carbon atom. The hypothesis of the asymmetric carbon atom f explains, in most cases, optical activity and the isomerism of optically active organic com- * " All optically active mediums are necessarily dissymmetric. In compounds which manifest the property of optical activity in the solid, dissolved and gaseous states, this activity can only be attributed to dissymmetry occurring in the mole- cules themselves." [Hantzsch.] Dissymmetric molecules (that is, molecules of the same shape but not super-imposable), could not occur if their atoms were in a state of chaotic movement (page 32). The crystals of such a compound as tartaric acid are dissymmetric (one form is dextro- another levo-rotary). Each particular crystal of tartaric acid is composed uniformly of dissymmetric molecules of the same rotary direction. Like the molecules in a magnet the dissymmetric molecules of an opti- cally active crystal are doubtless polarized. f An asymmetric carbon atom is an atom which is linked to other atoms or radi- cals in such a way that it " no longer contains the elements of symmetry" (page 39). Chemical Constitution of Organic Substances. 37 pounds.* We have already learned that there are three secondary butyl carbinols, two of which are optically active, while the third is inactive. The optically active substances cause equal though opposite rotations. Each of these isomers contains a single asym- metric carbon atom. The occurrence of three such modifications is a necessary consequence, as we shall see, of the presence in each of the molecules of one asymmetric carbon atom (foot-note, p. 40). " The tetra-valency of the carbon atom has its origin in four points of attraction, situated on its outer surface, so that it is able to link itself to atoms or groups of atoms in four directions. Concerning these directions various assumptions can be made. They may, for example, be supposed to lie in one plane. But this assumption is untenable, as will be seen by considering a di-substitution product of methane, for example, such as the compound Ca2b2, in which a and b represent any dissimilar atoms or radicals, and C the carbon atom. If the four linkings lie in one plane, such a compound may be represented by either one of the following formulas: These formulas are different, because in the first case the like atoms or radicals are separated from one another by the unlike ones, while in the second case, the like atoms or radicals are adjacent to one another. It follows from this that, in general, two isomers must exist in the case of all compounds Ca2b2, if our original assumption was correct. But experience teaches that such isomers do not exist. Among the many hundreds of compounds of this type there is no * Inorganic compounds are optically active only in the crystalline state. The optical activity of an inorganic crystalline mass disappears when the mass is con- verted into an amorphous condition, or when it is dissolved in a liquid, or when it is rendered gaseous. Optical activity in inorganic compounds depends, therefore, on the structure of the crystal itself. We have already noted the fact that optically active organic substances retain their optical properties when the substances are in solution, and even when they are in the gaseous state (p. 35). In the cases of the inorganic optically active substances, the geometric relations of the molecules in the solid masses are the primary factors. Optical activity of organic substances on the other hand, depends on the geometric relations of the atoms in the molecules. Chemical Notes. 38 known instance of the occurrence of two isomeric forms.* The particular assumption that the directions of all four linkings of a carbon atom lie in the same plane must therefore be abandoned, being at variance with the facts. " The most general assumption that can be made in regard to these directions is that each pair of them lies in the same plane. They are then distributed in space in such a way that, if the carbon atom is regarded as situated inside an irregular tetrahedron, the direc- tions of the linkings will be toward the angles of the figure. (Fig. 1.) "We shall now ascertain whether this mode of representation is in accordance with the facts. If the directions of the linkings make different angles with one another, there still remains possible a difference in the structural arrangement of compounds Ca2b2, because it is just as easy to imagine that the atoms or radicals a2 are connected with the linkings which have the smallest angle between them, as it is to imagine that they are joined with those which make the greatest angle with one another. In the case of com- pounds Ca2b2 there is, however, only one arrangement possible when the directions of the linkings meet at equal angles. This is the case when the carbon atom is regarded as being situated at the center of a regular four-sided figure {tetrahedron, Fig. ff, with its linkings directed toward the angles. By putting the members of the groups a2 and b2 in different positions in two such atom models, it is always possible by rotating the models to bring them into such a position that the like atoms (or radicals) coincide, showing that the two forms are identical. This representation of the direction of the linkings explains why it is that there are no isomers of a com- pound such as Ca2b2.f " In the case of compounds Cabcd, which contain four different atoms (or radicals) attached to the carbon atom, which is then an asymmetric carbon atom, our representation indicates the possibility Fig. 1. * There are also no known optical isomers of the formulas, Ca2bc, Cab2c, Cabc2. There are no isomeric mono-substitution products of CH4. f These remarks also apply to substances of the formulas referred to in the above footnote. See page 37. Chemical, Constitution of Organic Substances. 39 of the existence of two isomeric forms. It is seen from figures 2 and 3 that for these four atoms (or radicals) there are possible two arrangements, which cannot be made to coincide with one another in any position, although they resemble one another in the same way that an object resembles its reflection in a mirror. * A figure of this kind has no plane of symmetry, hence the name ' asymmet- ric carbon atom.' This makes it possible to understand how one Fig. 2. Fig. 3. isomer is just as much dextro-rotary as the other is levo-rotary (page 40). It is, in fact, the arrangement of the groups relative to the asymmetric carbon atom which is the cause of the rotation of the plane of polarization. If the arrangement of the atoms (or radicals) in Fig. 2 produces dextro-rotation, then the inverse ar- rangement in the isomer in Fig. 3 must of necessity cause an equal rotation, but in an opposite direction. "It has been stated above (p. 37) that not merely two, but three, isomers occur when there is one asymmetric carbon atom present in the molecule : a dextro-rotary, a levo-rotary and an optically * "If a compound contains an asymmetric carbon atom, we can conceive of its existence in at least two isomeric modifications, the one being an image of the other, as is indicated by the tetrahedra below, which show only the positions at the four summits : Fig. 4. Fig. 5. " In the left tetrahedron (Fig. 4) the successive series of atoms or radicals, b, a, d, united to the asymmetric central carbon atom, proceeds in a direction oppo- site to that of the hands of a watch, while in the right tetrahedron (Fig. 5) the course of the same series coincides with that of the hands of a watch. The two fig- ures cannot be brought, by rotation, into the same position-that is, in a position to cover each other completely-any more than the left hand can be made by the same means to cover the right, or a picture its image." [Richter.] 40 Chemical Notes. inactive isomer. It has been proved that the optically inactive material is composed of equal parts of the dextro-rotary and the levo-rotary compounds. Since these rotations are equal in amount, but different in direction, their sum has no effect upon the plane of polarization."* [Holleman. J The asymmetric carbon atom is commonly indicated, in printed formulas, by an italic C, or a heavy faced C, or by an * placed be- fore the usual carbon symbol. (See foot-note, p. 34.) The more important facts connected with optical isomers con- taining a single asymmetric carbon atom may be summed up briefly as follows : 1. All optically active organic compounds contain at least one asymmetric carbon atom. 2. There are no optically active organic compounds that do not contain at least one asymmetric carbon atom. 3. The optical activity of an organic compound disappears when the asymmetric carbon atom becomes symmetric, i. e., when two or more of the atoms (or radicals) united to the carbon atom are identical. 4. All optically active organic compounds occur in two optically active forms, which are identical in rotary power, but opposite ( " dextro " and " levo " ) in rotary direction. 5. Optically inactive organic materials containing one asym- metric carbon atom per molecule are equimolecular mixtures or equimolecular ("racemic") compounds of dextro- and levo-rotary isomers. Saturated compounds containing two or more asymmetric carbon atoms. The relationships of optical isomers become more and more complicated as the number of asymmetic carbon atoms increases. " Substances containing one asymmetric carbon atom exist, as we have seen, in two optically active modifications which may be rep- * Among the substances of biological importance that illustrate these facts are the lactic acids (oxy-propionic acids), with formulas as follows : fZ-lactic acid + Z-lactic acid = inactive lactic acid, or the so-called "fermenta- tion" lactic acid (p. 37). Chemical Constitution of Organic Substances. 41 resented by + A and - A, if one designates by A the rotary power of the asymmetric group. Compounds with two asymmetric car- bon atoms of the general formula Cabc-Cdef,* are active by rea- son of an active group A, and another active group B, each of which can exist in two active modifications. Such compounds yield four optical isomers. . . . " Compounds with three asymmetric carbon atoms of the general formula Cabc - Cde - Cfgh, contain three active groups, A, B and C. There are then 23 ( = 8) isomers possible. . . . Substances Fig. 6. Fig. 7. Fig. 8. Dextro-tartaric acid + levo-tartaric acid = (4) Inactive or racemic acid containing four asymmetric carbon atoms of the formula Cabc - Cde - Cfg - Chij, will yield 24 (=16) isomers, and so on." [Hantzsch.] The simplest compounds containing only two asymmetric carbon atoms would be those in which two identical groups were united to the two asymmetric carbon atoms. Under such conditions one carbon-containing half of the molecule would be chemically like the other. The tartaric acids, four in number, are of this nature, formulas and models of which are given above (Figs. 6, 7 and 8). 30. Geometric isomers. "Two carbon atoms singly linked to each other, whose valences, not required for mutual union, hold other atoms or atomic groups, should be considered as able to rotate independently of each other about their axis of union. It is assumed, however, that the atoms or atomic groups combined * The letter C represents an asymmetric carbon atom. The small letters repre- sent any different atoms or radicals combined with each carbon atom. 42 Chemical Notes. with these two carbon atoms exercise alternately a ( directing influ- ence' upon each other, until finally the entire system has passed into the 1 favorable configuration ' or the ' preferred position.' It follows from this assumption that, in ethane derivatives in which asymmetric carbon atoms are not present, structurally identical isomers could not occur. When the tetrahedron models are em- ployed to represent two systems united to each other by carbon atoms singly linked, then the two systems rotating independently of each other about a common axis move each in the solid angle of a tetrahedron. (Compare the projection formulas of the tartaric acids, Figs. 6, 7 and 8.) ... A different state prevails where the carbon atoms are doubly linked. The double union prevents a free and independent rotation of the two systems and space isomers are Fig. 9. Fic. 10. possible. The tetrahedron models represent this double union in such a manner that two tetraheda have two summits in common and arrange themselves about a common edge. The differences in chemical deportment of this class of isomers are frequent and im- portant. They are to be attributed to the greater or less spatial removal of the atomic groups which determine the chemical char- acter." [Richter.] Compounds containing two atoms of carbon united by a double bond. Compounds having the general formulas abC = Cab, abC = Cac, or abC = Ccd (ethylene in character) may exist in two isomeric modifications, as in the case of the two ethylene di-car- boxylic acids, fumaric acid and maleic acid, whose configurations and formulas are given'above.* * The differences in the structure of optical and geometric isomers are shown, not only in different physical and chemical properties, but even in physiological Chemical Constitution of Organic Substances. 43 Isomers having the general structure shown in Fig. 9, in which atoms or radicals of the same kind are directed toward the same sides of the molecule, are in the "plane symmetric configuration." Isomers having the general structure shown in Fig. 10, in which atoms or radicals of the same kind are directed toward opposite sides of the molecule, are in the "central or axially symmetric configuration." Compounds containing two atoms of carbon united by a triple Fig. 11. bond. The configuration of compounds of the general formula aC = Ca, or aC = Cb (acetylene in character) is indicated in Fig. 11. Such a configuration (two tetrahedra with three corners and one surface in common - double three-sided pyramid) excludes the possibility of isomerism, for differences in the relative positions of the atoms or radicals united to the carbon atoms cannot occur.* 31. Ring formation. The tetrahedral theory is the basis for our conceptions of the configuration and isomerism of certain cyclic compounds. Thus, for example, tri-methylene may be represented by the following formula and model (Fig. 12): Fig. 12. Isomers occur among such cyclic compounds, when the atoms or radicals in some or all of positions a and b (Fig. 12) are different. action, as the student of pharmacology soon observes. Thus, for example, the in- jection of a certain minimal amount of maleic acid will kill a dog very quickly. On the other hand, injection of the same quantity of fumaric acid into a dog of the same size, has hardly any observable toxic action. * Geometric isoomerism also occurs among nitrogenous organic substances. CHAPTER II. GENERAL PHYSICO-CHEMICAL PROPERTIES OF ORGANIC SUBSTANCES. 32. The physical properties as well as the chemical qualities of substances are determined by molecular composition and structure. A number of physical properties are known to bear very constant relations to certain observed kinds of composition and to several forms of molecular constitution. Crystallinity. 33. The crystalline form of an organic compound is usually a distinguishing physical feature. Many organic substances crystal- lize in two or more forms (fi-morphous, poly-morphous). Each crys- talline form is usually characterized by definite conditions of pro- duction and existence. The crystalline forms of isomeric substances are always different. "That the slightest difference in chemical constitution finds ex- pression in differences in crystalline form is demonstrated by the optically active carbon derivatives. Many optically active sub- stances possess a hemihedral form,* and the two optically active modifications of a carbon compound, although they exhibit the same geometric constants, are distinguished by peculiar left and right types. They are not superposable (29). The differences be- tween two optically active modifications, in which the atoms are similarly combined, is only due, according to the hypothesis of an asymmetric carbon atom, to the difference in arrangement of the atoms within the molecule (page 35). From this it follows that this variation in arrangement finds expression in the crystalline forms." [Richter.] Melting Point. 34. Every pure organic compound, if fusible or volatile, melts at a definite temperature. Impurities change the melting point of a * Hemihedrism is the property of crystals in virtue of which they have only half the number of plane surfaces required by normal symmetry. 44 Properties of Organic Substances. 45 substance. Consequently, melting point determinations are of value not only for the identification of a substance, but also in ascertain- ing its purity. The melting point of a pure organic compound is unaffected by recrystallization. Therefore, changed melting point after recrystallization is due to removal of impurity. Constancy of melting points, after several recrystallizations of a substance, implies complete purification. Variations in pressure affect melt- ing point only very slightly. Boiling Point. 35. Pure organic compounds that may be vaporized without decomposition, boil at definite temperatures under uniform condi- tions of pressure. Pressure affects boiling point very materially. Boiling point, like melting point, is affected by impurities and is of similar value in the differentiation or the purification of organic substances. Substances having different boiling points may be roughly separated, when in mixtures, by fractional distillation. " Generally the boiling point rises with the complexity of the molecule. The unsaturated compounds boil at higher tempera- tures than the saturated compounds of the same carbon content. With isomers having an equally large carbon nucleus those of normal structure possess the highest boiling points. These fall with the accumulation of methyl groups." [Richter.] Solubility. 36. The organic compounds show wide differences in solubility. The hydrocarbons are insoluble or only very slightly soluble in water, but as a rule they dissolve readily in alcohol and in ether. The more oxygen an organic substance contains the more readily it dissolves in water. The more the hydrocarbon derivatives diverge from the true hydrocarbon characters the more soluble they become in water and the less soluble they are in alcohol and ether. Many carbon compounds are soluble in one or more of the follow- ing additional solvents : chloroform, carbon di-sulfid, carbon tetra- chlorid, acetone, glacial acetic acid, benzene, anilin, petroleum ether, etc. The solubility of an organic compound is not only influenced by temperature, but is also so constant for a definite temperature, 46 Chemical Notes. that the solubility coefficient furnishes a means for the identifica- tion of organic compounds. Optical Properties. 37. Color. Most organic substances are colorless although many are colored. A large number of the colored organic compounds can impart their colors to vegetable or animal fibers, directly or indi- rectly through the agency of mordants.* Most of the colored organic compounds are members of the benzene series. 11 According to Witt a benzene compound is a dye when it con- tains a chr.omophorous group, e. g., NO2, N2, etc., and when, in addition, an acid or basic group, e. g., one or several OH, SO3H, CO2H, and one or several NH2 groups, enter the chromogen, i. e., a substance having a chromophorous group." [Richter.] 38. Rotation of the Plane of Polarized Light. Many organic compounds, in liquid or in dissolved condition, rotate the plane of polarized light (29). Most organic substances are optically inac- tive (29). Each optically active substance has, under uniform conditions, a definite rotary power. The specific rotary power of a substance varies with the temperature and is also influenced by the nature and proportion of the solvent. Electric Conductivity. 39. Most organic substances are non-conductors, i. e., non-electro- lytes. Only a minority of the carbon-containing compounds are dissociable. Chief among the ionizable organic substances are the acids and bases and salts. None of these are as strongly dissociable as most of the corresponding classes of inorganic compounds. Osmotic Pressure. 40. The soluble, undissociable organic compounds manifest nor- mal osmotic pressures, the dissociable compounds show abnormal osmotic tendencies. In these respects the organic compounds are qualitatively like the inorganic compounds. * A mordant is a substance, used in dyeing, which has an affinity for, or which can permeate, the material to be colored. A mordant may combine with the col- oring matter employed and form an insoluble colored compound within or about the fibers. Properties of Organic Substances. 47 Heat of Combustion. 41. Every pure organic substance has a specific heat of combus- tion. Traces of impurity may be detected, by the combustion method, in organic substances whose heat of combustion is known. " The quantity of heat evolved in any chemical change is a measure of the total work both physical and chemical, occurring in it. The determination of the quantity of heat developed in com- plete combustion is alone adapted for the determination of the energy- content of carbon compounds." [Richter.] The "fuel value" of the carbonaceous foods is measured in terms of heat of combustion. Among the regular differences observed in heats of combustion is the constant increase of 158 cals in the heat of combustion of the paraffins and olefins, and other hydrocarbons, for each differ- ence of CH2 in the compounds. Action of Heat. 42. Organic compounds are usually much less stable under the influence of heat than the inorganic substances. Many organic substances are readily decomposed by heat with the separation of carbon. " Some organic compounds, when heated at the ordinary temper- ature, rearrange themselves without alteration of their molecular magnitude, while some polymerize. Compounds, volatilizing unde- composed at ordinary pressure, decompose when their vapors are conducted through tubes heated to redness, and, as a rule, new bodies are formed together with partial carbonization. The split- ting oft* of hydrogen, the halogens, haloid acids, water and ammo- nia leads to a more intimate union of the already combined carbon atoms, and carbon atoms which previously were not united with one another not infrequently combine to yield carbocyclic and heterocyclic compounds." [Richter.] Action of Light. 43* Light exerts a very marked influence on many organic com- pounds. In many cases no action is observable. Light brings about decomposition, synthesis and rearrangement of many organic compounds. So marked is the decomposing action of light on 48 Chemical Notes. some organic substances that it is necessary to preserve them in dark rooms or in opaque vessels or in bottles of brown colored glass (69). The brown colored glass, in such cases, absorbs the actinic rays. Few organic dyes, for example, are fast colors. Most of them are bleached in the light. 44. Important synthetic products may be made with the aid of the electric current. Thus, for example, carbon and hydrogen may be converted into acetylene by passing the electric spark over carbon electrodes in an atmosphere of hydrogen, and acetylene and nitrogen yield hydrocyanic (prussic) acid under similar con- ditions, according to the following reactions : Action of Electricity. Many organic compounds may be radically transformed by elec- tricity. Thus, for example, acetic acid may be converted, by the electric current, into ethane and by-products, according to the fol- lowing reaction (61) : General Reagents Employed in Organic Chemistry. " The following are the most important (general) reagents used in organic chemistry: 45. Oxidizing agents. (1) Nitric acid (dilute and concentrated): 2HNO„ = 2NO 4- H2O + 30 (2) Potassium permanganate in acid or alkaline solution : 2KMnO, + 3H9SO4 = K2SO4 + 2MnSO. + 3H2O + 50 4 1 2 4 2 4 1 4 1 2 1 2KMnO4 + H9O = 2KOH + 2MnO2 +30 4'2 ' a (3) Potassium di-chromate and sulfuric acid : K„Cr O7 + 4H2SO, = K2SO. + Cr2(SO4), + 4H2O + 30 A A / A *1 it X AX */ O A Properties of Organic Substances. 49 (4) Chromium tri-oxid and glacial acetic acid : 2CrO3 + 6C2H4O2 = Cr2(C2H„O2)6 + 3H2O + 30 11 The use of a reagent in an organic solvent, like acetic acid, is of advantage on account of the solubility of organic substances in such solvents. 46. Reducing agents. "These may be divided into acid, neu- tral and alkaline reducing agents. Acid reducing agents. (1) Hydriodic acid : 2HI = I2 + H2 (2) Stannous chlorid and concentrated hydrochloric acid : SnCl2 + 2HC1 = SnCl4 + H2 (3) Tin or iron and hydrochloric acid : Sn + 4HC1 = SnCl4 + 2 H2 (4) Zinc dust and glacial acetic acid : Zn + 2C2H O = Zn(C2H3O2)2 + H2 Neutral reducing agents. (1) The zinc-copper or aluminium-mercury couple : ZnCu + 2H2O = Zn(OH)2 + Cu + H2 2AlHg + 6H2O = A12(OH)3 + Hg + 3H2 (2) Zinc dust and water : Zn + 2H2O = Zn(OH)2 + H2 Alkaline reducing agents. (1) Sodium amalgam, with alcohol or water : 2NaHg + 2H2O = 2NaOH + Hg + H2 (2) Sodium methylate : CH3ONa + O = HCO2Na* + H2 (3) Zinc dust and caustic soda : Zn + 2NaOH = Zn(ONa)2f + H2 * Sodium formate, f Sodium zincate. 50 Chemical. Notes. 47. The halogens. " The action of chlorin and bromin is in some cases promoted by light, and by the presence of small quanti- ties of certain metals and their salts, such as iron and aluminium, the chlorid or bromid of iron and antimony, also by sulfur and iodin. Such substances are called ' halogen carriers.' Their action is not fully understood. The chlorids and bromids of phos- phorus are also frequently used for introducing chlorin and bromin into organic compounds, especially in place of oxygen or of the hydroxyl (- OH) radical in the latter. 48. Dehydrating agents. " These agents are of two kinds. One kind is employed for removing moisture from organic substances. The common reagents for this purpose are sodium, fused calcium chlorid, potassium carbonate, calcium oxid, or sodium sulfate. Another class of dehydrating agents is used to remove the elements of water from organic substances, thereby converting them into new compounds. The most useful substances of this class are con- centrated sulfuric acid, phosphorus pent-oxid, and fused zinc chlorid." [Cohen.] CHAPTER III. THE PARAFFINS. [SATURATED HYDROCARBONS; MARSH GAS OR METHANE SERIES.] 49. Homologous Series. It has already been said that the great number of organic substances may be arranged in three main divisions^ as follows (16) : 1. Fatty compounds. 2. Carbocyclic compounds. 3. Heterocyclic compounds. Of these main groups the simplest and, in many respects, the most important biologically are the fatty compounds. Of the latter the simplest are the corresponding hydrocarbons (^paraffins). The hydrocarbons of any series of organic compounds are the " mother substances " of all the other compounds of the same group of organic substances, i. e., the latter arise from the hydrocarbons directly or indirectly, e. g., in the case of the paraffins, by the replacement of the hydrogen atoms of the hydrocarbons by other atoms or radicals. Thus, the paraffins are the parent substances of all the members of the fatty group of compounds. 50. Paraffin Series. Arranged according to the number of their carbon atoms, the paraffins form a typical homologous series. The paraffins are named in homologous order in the table on page 52, where certain physical data are also indicated. 51. Nomenclature. As a class, the paraffins are very resistant to chemical change. They have little affinity for ordinary chemical reagents. The term paraffin (derived from the latin parum, little, and affinis, affinity) has been applied to them for that reason. The first four paraffins were originally obtained from compounds of the mono-valent radicals, methyl, CH3, ethyl, C2H5, propyl, C3H7, and butyl, C4H9. Methane, for example, was originally called methyl hydrid (CH3-H). Later these hydrocarbons were given the names of their mono-valent radicals, with yl changed to ane. " Ane " 51 52 Chemical Notes. has since remained the termination of all the names of the paraffins. From pentane to the end of the series each paraffin is indicated by the name of the greek numeral corresponding to the number of carbon atoms contained in the paraffin. Paraffin Series. CnH2»+2 Name. Empirical Formula. Melting Point. Boiling Point at 760 mm. Pressure. Specific Gravity. Methane ch4 -186° 0. - 164° C. 0.415* Ethane c2h6 -172 - 84 0.4461 > Propane CaHo - 37 0.536 }■ 0 Normal butane. 1 1 0.600 J 0 Iso-butane J ^htjo - 17 Normal pentane 36 Iso-pentane - c5hI2 28 Tetra-methyl methane 1 10 Normal hexane 1 69 Iso-hexane 62 Methyl di-ethyl methane ■ C6Hu 58 Tetra-methyl ethane 64 Tri-methyl ethyl methane 48 Normal heptane 1 r ft 98 0.7001 Iso-heptane J 90 0.697 >> Octane c8h,« 125 0.719 5 Nonane CaHoa - 51 149 0.733 Decane - 32 173 0.745 ' Undecane - 26 194 0.7741 Dodecane c19h,b - 12 214 0.773 Tridecane Ci JELo - 6 234 0.775 Tetradecane C,,H>a 5 252 0.775 Pentadecane ^14 ^30 C,=H„ 10 270 0.776 Hexadecane c1kh,. 18 287 0.775 > Heptadecane CitH3G 22 303 0.777 * Octadecane 1 : 1 I 28 317 0.777 ® N onadecane ClqH,n 32 330 0.777 § Eicosane ConH.A 37 2051 0.778? 5 Heneicosane 40 215 £ 0.778 w Docosane 44 224 K 0.778 'S Tricosane 48 234 E 0.779 S' Tetracosane 51 243 -B 0.779 ' Heptacosane C27H56 60 270 0.780 Hentriacontane C31H61 68 302 " 0.781 Dotriacontane 70 310 S 0.781 Pentatriacontane CoJUa 75 331 0.782 Dimvric.vl 102 52. Isomers. The four affinities of the carbon atom are equal (20). Consequently there can be no isomers of the first three paraffins. Beginning with butane an increasing number of isomers is possible. See the summary on page 29. In the above table the best known isomers are indicated by italics. *At -164° C. The Paraffins. 53 53« Sources. Paraffins are formed in the ordinary decay of vege- table and animal matter. The volatile paraffins proceed from coal deposits. They are present in natural gas. They are also pro- duced in the decomposition of vegetable and animal matter through the action of heat. The most plentiful source is petroleum (54). 54. Petroleum. (" Naphtha/' " earth oil," " rock oil/' " min- eral oil," "crude oil.") Oil wells are to be found in most coun- tries, a fact indicating wide natural distribution of petroleum. Petroleum is supposed by some to have resulted from the action of steam on the iron carbid (Fe2C) of subterranean mineral deposits.* By others it is regarded as certain that petroleum has been pro- duced by the distillation of fossil plants and animals, under great pressure and at high temperatures. The latter view is supported by the fact that the distillation of fish blubber under pressure has given products similar to American petroleum. Samples of petroleum from different localities vary widely in chemical composition. In a crude state petroleum is a thick oily liquid, of brownish color with greenish lustre. On exposure to the air its more volatile constituents evaporate spontaneously and a thick residue called asphaltum ultimately results. American petroleum consists almost solely of normal paraffins. Small quantities of benzene (13) and naphthene f hydrocarbons are also present. Its specific gravity in crude form is 0.8 - 0.92. Various products of great value, consisting of mixed paraffins, are obtained from it by fractional distillation, among which the follow- ing are the most important: Fraction Name Boiling Point Constituents 1. Cymogene 0° c. - 2. Rhigolene 18 - 3. Petroleum etherf 40- 60 C5Hu-C6Hu * Mendelejeff suggests that the following reaction may take place in such a production of hydrocarbons : 3FemCn ^FlaO - wiFe3O4 -j- CsnHgm. Cast iron contains iron carbid. When cast iron is dissolved in HC1, hydrocarbons are liberated. Mendelejeff obtained in this way "a liquid mixture of hydrocar- bons exactly similar to natural petroleum in taste, smell and reaction." See methods of preparing methane, page 59. t Naphthene hydrocarbons are isomers of the ethylene hydrocarbons (13). tGasolin, which boils at 46°, is obtained from this product on redistilling. 54 Chemical Notes. Name Fraction Boiling Point Constituents 4. Petroleum naphtha (ligroin) 60-120° C. C6Hu-C8H18 5. Petroleum benzine* (benzolin) 120-150 C8H18 - c9h20 6. Kerosene (illuminating oil) 150-300 CioH22 C16H3t 7. Lubricating oil t Melting Point - 8. Vaselinef 30-40 - 9. Paraffin wax (paraffin)! 45-65 - 10. Petroleum pitch or coke - - 55. Preparation. " Although the paraffins occur in nature (53), and a few of them can be obtained in pure condition from natural sources, we are dependent upon synthetical operations per- formed in the laboratory for our knowledge of the series and the relations existing between them. We have already seen how ethane can be prepared from methane by treating methyl iodid with zinc or sodium (22), as represented in this equation : CH3I + CH3I + 2Na + C2H6 + 2NaI " This method has been extensively used in the building up of higher members of the series. Thus from ethane we can make ethyl iodid, and, by treating this with sodium, get butane, C4H10: C2HJ 4- C2HJ + 2Na = C4H1(1 + 2NaI Z 3 Z 3 4 1U But we can get the intermediate member, propane, C3H8, by mix- ing methyl iodid and ethyl iodid and treating the mixture with sodium : CH J + C„H J + 2Na = CH„-C„H, + 2NaI O 4 3 O A U By applying this method, it is plain that a large number of the members of the paraffin series might be made. " Another method consists in treating the zinc compounds of the radicals, like zinc ethyl, Zn(C2H5)2, with the iodids of radicals. Thus zinc methyl and methyl iodid give ethane; zinc ethyl and methyl iodid give propane ; zinc ethyl and ethyl iodid give butane, etc. : Zn(CH3), + 2 CH3I = 2C2H6 + Znl2 Zn(C2H5)2 + 2 CH3I = 2C3H8 + Znl2 Zn(C2H5)2 + 2C,H I = 2C4H10 + Znl2 *To be distinguished from the hydrocarbon, benzene, C6H6 (13). t The boiling point is above 300° C. The Paraffins. 55 Paraffins can be made by replacing the halogen in a substitution- product by hydrogen. This can be effected by nascent hydrogen or by hydriodic acid : C4H9I + H2 = C4H10 + HI Finally, the paraffins can be made by heating certain of their acid derivatives with an alkali. This can be illustrated by the prepar- ation of marsh gas from a salt of acetic acid, by heating the latter with caustic potash (133). The reaction may be written thus : KC2H3O2 + Potassium acetate KOH = CH4 + K2CO3 The products are a hydrocarbon and a carbonate." [Remsen.] 56. Properties. The simplest members of the paraffin series (from methane to tetra-methyl methane) are gaseous at the ordinary temperature. The intermediate members (to and including penta- decane) are, at ordinary temperature, colorless liquids with faint but characteristic odors. The highest members, beginning with hexa- decane, are crystalline solids at ordinary temperatures. (See page 52.) The highest members of the series volatilize (without decom- position) only under reduced pressure. The boiling points rise with increase of molecular weight, the difference for CH2 being 30° at first and varying from 25°-13° with the highest members. The paraffins are insoluble in water. The lower and intermediate members of the series dissolve readily in alcohol and in ether. Solubility in the latter reagents decreases as the molecular weight increases. Dimyricyl, for example, is almost entirely insoluble in them. The paraffins are lighter than water, and, being insoluble, float on water. Specific gravity increases with molecular weight. At their melting points, however, the higher paraffins have essen- tially the same specific gravity. Under ordinary conditions strong and dilute mineral acids have little effect on the paraffins and they are unchanged by ordinary oxidizing agents. When heated to a sufficiently high temperature the paraffins burn directly to carbon di-oxid and water. When acted on by chlorin or bromin the paraffins yield halogen substitu- tion products. By means of the latter products other derivatives may be readily obtained, among which are some important pharma- cological products (72). 56 Chemical Notes. 57. Substitution products. Nothing can be directly added, chemically, to the paraffins - if any chemical change takes place in them, hydrogen is first removed from the paraffin molecule and an equivalent of other atoms or radicals takes its place. We have already stated that, although the paraffins are very resistant to chemical change, chlorin and bromin are able to react with them. By replacement of hydrogen, halogen substitution products result. Chlorin and bromin are among the few reagents that are able to effect such an entrance into the paraffin molecule (65). The combination between the paraffin and the halogen in such cases, is quite different in nature from that which takes place be- tween such an inorganic compound as carbon monoxid and chlorin. The latter substances react as follows : CO 4- Cl2 Carbon monoxid = COC12 Carbonyl chlorid In this reaction the molecule of chlorin unites directly with the molecule of carbon monoxid. Nothing is separated from either in this process of union. Such a compound, which results from a complete union of two molecules, is called an addition product.* A synthetic reaction results. When chlorin acts on a paraffin, such as methane, there is only an exchange of atoms, i. e., a metathetic, not a synthetic, reaction takes place. Instead of addition there is substitution, as follows : CH4 4- 4 1 Methane CL Z = CH Cl + o' Methyl chlorid HC1 The replacement of hydrogen atoms of a hydrocarbon by an equivalent in single atoms or radicals is termed substitution. The compounds obtained in this way are substitution products. The most important organic substances, i. e., the hydrocarbon derivatives, are such substitution products. 58. Paraffin radicals. In the formation of substitution products of the paraffins (and other hydrocarbons, also) it has always been observed that although one hydrogen is replaceable with relative ease under certain conditions, it is increasingly difficult to replace *The paraffins {saturated hydrocarbons) do not form such compounds. The un- saturated hydrocarbons, such as the ethylenes, do form compounds of the additive type (21). The Paraffins. 57 additional hydrogen atoms. In the case of methane, for example, there is a very strong tendency for the carbon atom to retain its hold on three of the four hydrogen atoms in a vast majority of the changes through which it may pass. The CH3 group remains intact and, as in the case of the NH. radical, maintains its indi- viduality like a mono-valent atom. For this reason, as already indicated, the hydrocarbons were originally regarded as hydrids of mono-valent hydrogen-carbon radicals (51). In the transformation of one hydrocarbon into another this same tendency is observed, as was shown in the reactions on page 27. Each of the paraffins enters most of its reactions, therefore, as a mono-valent radical. The mono-valent radicals of the first six paraffins are named below : Paraffin Methane, CH4 Ethane, C2H6 Propane, C3H8 Butane, C4H10 Pentane, C5H12 Hexane, C6H14 Radical MethyZ, CH3 EthyZ, C2H5 Propyl, CsH7 But?/Z, C4H9 Pentyl, C5Hn Hexyl, C6H13 The generic name of these mono-valent radicals is alkyl.* Such a compound as CH3C1 is an alkyl chlorid. The similarity in combining tendency between the hydrogen atom and the methyl radical, for example, is shown in the follow- ing comparable reactions (79). 59. Paraffins of biological importance. Methane is the only paraffin that occurs as a hydrocarbon in animals. Its quantity in organisms is trifling (60). There are many paraffin derivatives, * The paraffin mono-valent radicals united with hydroxyls constitute the common alcohols. The term alkyl is an abbreviated form of alcohol and yl, the ending of the names of the radicals (75). These radicals were first recognized in the alcohols. 58 Chemical, Notes. however, in both animal and vegetable organisms. Of these var- ious derivatives, all but a few are substitution products of the very simplest paraffins. In the case of the elements, organisms are com- posed chiefly of those of loivest atomic weights. In the case of the carbon-containing compounds in organisms, there is an analogous predominance of derivatives of the paraffins of the lowest molecular weights, i. e., from methane to, and including, hexane. Some of the animal and vegetable fats and albuminous matters contain radicals that are derivatives of hexadecane and octadecane. 6o. Methane. (Marsh gas, fire damp.) Methane is the only hydrocarbon containing one atom of carbon. Its formula, CH4, is written constitutionally as follows : Occurrence. Methane is produced during the bacterial decom- position of organic matter. For this reason it is constantly rising from stagnant water, especially in marshy districts (marsh gas), and its production in small quantities in the intestines of animals, by the following reaction, is due to the same cause; c6h10o5 Cellulose + H2o = 3CH + 4 ' Methane 3CO2 Methane is the only hydrocarbon occurring free in animals. Meth- ane is also associated with coal deposits and, mixed with air in mines (fire damp), it forms an explosive mixture. Methane also arises from the earth with other gases in the vicinity of oil wells (natural gas) and is a constituent of petroleum. It is present also in illumin- ating gases. It forms about 40 per cent, of the gas obtained on distilling coal. Synthesis. The synthesis of methane is a matter of great import- ance, because it is the simplest of the paraffins - the mother sub- stance of all the parafins and their derivatives. The following sample reactions show how methane may be made from the elements: A. By the direct union of carbon and hydrogen, at 1200° C., or The Paraffins. 59 by passing an electric discharge between carbon electrodes in an atmosphere of hydrogen : C + 2H2 = CH4 B. (1) When sulfur vapor is passed over red-hot charcoal, car- bon di-sulfid results: c + s2 = cs2 (2) When hydrogen and sulfur vapor are passed together through a red-hot tube, hydrogen sulfid is formed : 2H2 + S2 = 2H2S (3) When carbon di-sulfid and hydrogen sulfid are together passed over red-hot copper, methane is one of the resultant products : CS2 + 2H2S + 8Cu = CH4 + 4Cu2S C. (1) Water may be made by burning hydrogen : 2H2+O2=2H2O (2) If water vapor is substituted for hydrogen sulfid in reaction B, 3, methane is among the products formed : CS2 + 2H2O + 6Cu = CH4 + 2Cu2S + 2CuO D. (1) In the electric furnace aluminium and carbon unite to form aluminium carbid: 3C + 4A1 = C,AL (2) By treating aluminium carbid with water (formed as in reac- tion C, 1), methane is one of the resultant products : C3A14 + 12H2O = 3CH4 + 4A1(OH)3 Properties. Methane is a colorless, odorless gas. It burns with a pale blue, faintly luminous flame, to carbon di-oxid and water. It is compressible to a liquid under great pressure and at low temper- atures. Its critical temperature is - 82° C. Its critical pressure, 55 atmospheres. Under 760 mm. pressure it boils at - 164° C. At - 164° C. its specific gravity is 0.415. The melting point of the solid is - 186° C. Its mixtures with oxygen or air explode violently when fired. Direct sunlight explodes its mixture with 60 Chemical Notes. chlorin. Continuous electric sparking converts it into carbon and hydrogen. It resists most chemical reagents, but its halogen sub- stitution products render possible the production from methane of ethane, alcohol, acetic acid and many other products. 61. Ethane is the second member of the paraffin series. Its formula, C2H6, may be written in constitutional form as follows : Occurrence. Ethane occurs with methane in petroleum and in the gases from oil wells. Synthesis. Like methane, ethane may be formed in minute quan- tities by sparking carbon electrodes in an atmosphere of hydrogen. 2C + 3H2 = C2H6. Ethane was first produced by the electrolysis of potassium acetate as follows: * Ethane may also be prepared by the action of sodium on methyl iodid, in a reaction as follows : * In this reaction two molecules of potassium acetate and two molecules of water are transformed. The formulas are arranged graphically to show clearly the fate of the several parts. ' ' The salt breaks down into potassium, its electro-positive constituent appearing at the negative pole (-) and separating hydrogen from water at that point, and also into the unstable radical CHS-CO, which imme- diately decomposes at the electro-positive pole (+) into - CH3 and CO2. Two methyl groups then unite to form ethane (di-methyl), just as two hydrogen atoms combine to form a molecule of that element." [Richter.] The Paraffins. 61 " This process represents not only a general synthetic method by which many of the paraffins may be built up, but is one of great theoretical importance. It affords strong evidence in support of the theory of the linking of carbon atoms. As the removal of an atom of iodin from each molecule of methyl iodid leaves one carbon bond free, it must be by this single residual bond that the carbon atoms are united." [Cohen.] There are numerous other methods for the preparation of ethane. Properties. Ethane is a colorless and odorless gas. It burns with a faintly luminous flame, to carbon dioxid and water. Its critical temperature is 34° C. Its critical pressure is 50.2 atmospheres. Under 760 mm. pressure it boils at - 84°. The specific gravity of the liquid at 0° C. is 0.466. The melting point of the solid is - 172° C. 62. Propane is the third member of the paraffin series. Its formula, C3H8, may be written in constitutional form as follows : Occurrence and synthesis. Propane is a constituent of crude oil and is present in the gases issuing from oil wells. It may be made from ethyl iodid and methyl iodid by one of the usual paraffin synthetic methods, as follows (55) : Properties. Propane is a colorless, odorless gas at ordinary tem- peratures, but is readily condensed at low temperatures. It burns with a slightly luminous flame. Its liquid form boils at - 37°, under a pressure of 760 mm. At 0° C. its specific gravity is 0.536. 62 Chemical Notes. 63. Butanes, pentanes, hexanes and the remaining paraffins are of less consequence to the biologist than the preceding members of the paraffin series (59), and we may conclude our study of these hydrocarbons with the following observations on isomerism among them, which review and extend the statements made on pages 30 and 31 : 64. Isomerism among the paraffins. No isomers of methane, ethane or propane. " It has already been stated that the evidence is conclusive that each of the four hydrogen atoms of marsh gas bears the same relation to the carbon, and hence we believe that, as regards the nature of the product, it makes no difference which hydrogen atom is replaced by a given atom or radical (20). Accord- ing to this, as ethane is the methyl derivative of marsh gas, it makes no difference which of the hydrogen atoms of marsh gas is replaced by the methyl, the product must always be the same, or there is but one ethane possible accordina to the theory. This is renresented bv the formula In ethane, as well as in methane, all the hydrogen atoms bear the same relation to the molecule, and it should make no difference which one is replaced by methyl. But propane is regarded as derived from ethane by the substitution of methyl for hydrogen; and, as it makes no difference which hydrogen is replaced there is but one propane possible. Only one has ever been discovered, and this must be represented thus : Butanes. a Continuing the process of substitution of methyl for hydrogen, it appears that the theory indicates the possibility of the existence of two compounds of the formula C4H10. One of these should be obtained by replacing by methyl one of the three hydro- gens of either methyl group of propane. It is represented by the formula: TT TT TT TT The Paraffins. 63 The other should be obtained by replacing by methyl one of the two hydrogens of the group CH2 contained in propane. This would give a hydrocarbon of the formula : The theory then indicates the existence of two butanes. How about the facts? Two, and only two, butanes have been discov- ered. The first, which occurs in American petroleum, has been made synthetically by treating ethyl iodide with zinc : 2CH - CH„I + Zn = CH3-CH2-CH2-CH3 + ZnL. O A a u L ° a The method of synthesis clearly shows which of the two possible isomers the product is. It is known as normal butane. It is a gas which can be condensed to a liquid at 1° C. The second, or iso-butane, is made from an alcohol having the structure repre- sented by the formula by replacing the hydroxyl by hydrogen. It is a gas which becomes liquid at - 17° C. The differences between the two butanes are observed principally in their derivatives. Pentanes. "Applying the same method of consideration to the next member of the series, how many isomeric varieties of pentane, C5H12, may we expect to find ? The question resolves itself into a determination of the number of kinds of hydrogen atoms contained in the two butanes, or the number of relations to the molecule represented among the hydrogen atoms of the butanes. We can make this determination best by examining the structural formulas. Take first normal butane : In this there are plainly two different relations represented ; viz., 64 Chemical Notes. that of each of the six hydrogens in the two (terminal) methyl groups, and that of each of the four hydrogens of the two (inter- mediate) CH2 groups. The two possible methyl derivatives of a hydrocarbon of this formula are therefore to be represented thus: we see that it consists of three methyl groups, giving nine hydrogen atoms of the same kind, and one CH group, the hydrogen of which bears a different relation to the molecule from that which the other nine do. There are therefore two possible methyl derivatives of iso-butane which must be represented thus : We have, therefore, apparently four pentanes. But on comparing formulas (2) and (3), it will be seen that, though written a little differently, they really represent one and the same compound. Thus the number of pentanes, the existence of which is indicated by the theory, is three, and these are represented by formulas (1), (2) and (4). They are all known. The first is called normal pentane, the second iso-pentane or di-methyl ethyl methane, and the third tetra-methyl methane. " It would lead too far to discuss all the methods of preparation and the properties of these hydrocarbons. It will be seen that the methods of preparation show what the structure of a hydrocarbon is. Di-methyl ethyl methane is made from an alcohol which can be shown to have the formula by replacing the hydroxyl by hydrogen. Hence its structure is that represented above by formulas (2) and (3). The Paraffins. 65 "Tetra-methyl methane is made by starting with acetone. Acetone has been shown to consist of carbonyl in combination with two methyl groups, as represented in the formula CH3-CO-CH3. It has also been shown that, by treating acetone with phosphorus pen- ta-chlorid (PC15), the oxygen is replaced by chlorin, giving a com- pound of the formula CH3-CC12-CH3, acetone chlorid (99). Now, by treating this chlorid with zinc methyl, Zn(CH3)2, the chlorin is replaced by methyl thus : The product is tetra-methyl methane, and the synthesis thus effected shows at once what the structure of the product is. Hexanes. "The student will now be prepared to apply the theory to the determination of the possible number of hexanes. He will find that there are five. The theory is, in this case as in the preceding, in perfect accordance with the facts. There are five and only five hexanes known. Only the names and formulas of these will be given here : " Passing upward, we find that nine heptanes are possible accord- ing to the theory, while but four have thus far been discovered ; and that, while theory indicates the possibility of the discovery of eighteen hydrocarbons of the formula C8H18, but three are known. The theoretical number of isomeric varieties of the highest mem- 66 Chemical Notes. bers of the series is very great (24), but our knowledge in regard to these highest members is very limited, and it is impossible to say whether the theory will ever be confirmed by facts. It may be that there is some law limiting the number of complicated hydrocarbons. Classification according to carbon linkage. u On examining the formulas used to express the structure of the hydrocarbons, we find that they can be divided into three classes: (1) Those in which there is no carbon atom in combination with more than two others ; as,- Propane, CH - CH - CH3 Normal butane, CH,-CH -CH2-CH Normal pentane, CH- CH2-CH2- CH2- CH3 and Normal hexane, CH-CH,-CH-CH-CH,-CH, ' u Z A A L o (2) Those in which there is at least one carbon atom in combin- ation with three others; as,- (3) Those in which there is at least one carbon atom in combin- ation with four others; as,- 11 The members of the first class are called normal paraffins ; those of the second class, iso-paraffins; and those of the third class, neo-paraflins. The Paraffins. 67 " Only the members of the same class are strictly comparable with each other. Thus it has been found that the boiling-points of the normal hydrocarbons bear simple relations to each other, and that the same is true of the iso-paraffins (50) ; but, on comparing the boiling-points and other physical properties of normal paraffins with those of the iso- or neo-paraffins, no such simple relations are observed." [Remsen.] CHAPTER IV. HALOGEN DERIVATIVES OF THE PARAFFINS. Substitution in General. 65. We have already noted the fact that the paraffins are saturated compounds, i. e., that the valences of each carbon atom in them are fully satisfied (17). Consequently, no more atoms can be added directly to the paraffin molecule. Chemical changes in the paraffin molecule occur only by substitution, never by direct addition. These facts were indicated briefly on page 21. Hydrocarbons in general are resistant to most chemical influ- ences. They are easily transformed, however, by a few reagents such as chlorin and bromin, nitric acid and sulfuric acid. Through the action of such reagents a very large number of derivatives can be made. Such derivatives differ from the hydrocarbons from which they may have been produced, in containing one or more atoms or radicals in place of equivalences of hydrogen atoms. When chlorin is allowed to act upon methane in diffused day- light reaction occurs. There is a gradual transformation of the paraffin. Hydrochloric acid is evolved in gaseous form and one or more substitution products result, according to the vigor of the reaction and the length of time it proceeds. These products may be one or more, having the following formulas : ch3ci, ch2ci2, chci3, CC14 The characters of these formulas indicate that in such an action on methane, chlorin replaces one methane hydrogen after another until all of them are removed from the methane molecule. It is impossi- ble for more than four chlorin atoms to unite with the carbon atom. With each substitution of a hydrogen atom in methane by a chlorin atom, a new saturated compound is produced. As in the case of methane itself, nothing can then be added directly to the compound. The progressive reaction between chlorin and methane may be represented by the following four equations : 68 Halogen Derivatives of the Paraffins. 69 (1) CH4 + Cl2 = CH3C1 + HC1 (2) CBLC1 + CL = CH2C19 + HC1 (3) CH2CL + CL = CHCL + HC1 (4) CHC13 + Cl2 = CC14 + HC1 This particular process of substitution is not very practical. It is difficult to stop the reaction at any particular point. The product is usually a mixture of substances. Any of the halogen compounds may be readily produced, however, by treating a cor- responding alcohol with a halogen acid, as in the following sample reaction : C2H6O + Ethyl alcohol HC1 = C2H5C1 + Ethyl chlorid h2o In this reaction a chlorin atom replaces a hydroxyl, OH, radical in the alcohol. This reaction, like many reactions between organic compounds, is reversible. When methyl chlorid is treated with water, methyl alcohol results. The reversibility of the reaction may be indicated as follows : c2h6o + HC1 Tt c2h5ci + h2o We see at a glance that such halogen compounds bear intimate chemical relations to the alcohols (74). According to the number of introduced halogen atoms, the sub- stitution products of a paraffin are known as mono-, di-, tri-, tetra-, etc., halogen derivatives of that hydrocarbon. There are many such derivatives that contain different halogens in the same molecule. 66. General properties of halogen derivatives. The halogen derivatives of the lower paraffins are heavier than water and are insoluble in it. They do not burn readily. Some are inflammable. They possess an agreeable, penetrating odor. A few of them are useful as anaesthetics (69). Mono-halogen derivatives. 67. As was stated above, derivatives containing chlorin or bromin can be made by direct interaction between the paraffin and either of these two halogens. lodin does not react directly. The alkyl fluorids are relatively unimportant. The best method of production 70 Chemical Notes. depends upon the reaction between the alcohols and halogen acids, as in the following case (79) ch4o + Methyl alcohol HI = ch3i + Methyl iodid h2o The mono-halogen paraffins are connected, by reactions, with the alcohols, as the above equation indicates. The following compara- tive formulas indicate that the mono-halogen paraffins may be re- garded as haloid acids in which the hydrogen atoms have been replaced by paraffin radicals (79): HF HC1 HBr HI (HOH) CH3F CH3C1 CH3Br CH3I (CH3OH) A few of the most important mono-halogen products are indicated below: Mono-halogen Derivatives of the Lower Paraffins. CnH2n+iR Formula. Boiling Point at 760 mm. Pressure. Specific Gravity. Methyl chlorid CH3CI -24° C. 0.952 atO° C. Ethyl chlorid C2H5C1 12 0.918 " 8 Propyl chlorid C3H7C1 44 0.912 " 0 Iso-propyl chlorid CsH7C1 36 Methyl bromid CH,Br 4 1.732 at 0 Ethyl bromid C3H5Br 38 1.468 " 13 Propyl bromid C3H7Br 71 1.383 " 0 Iso-propyl bromid C3H7Br 59 Methyl iodid CH3I 43 2.293 at 18 Ethyl iodid C2H5I 72 1.944 11 14 Propyl iodid c3h7i 102 1.786 " 0 Iso-propyl iodid cXi 89 Of the above mono-halogen compounds all but the methyl and ethyl chlorids and the methyl bromid are either fluid or solid at ordinary temperatures. Methyl chlorid, or chlor-methane, CH3C1 is a sweet smelling gas. It may be readily condensed at low temper- atures. It boils at - 24° C. Evaporation of the fluid is produc- tive of a low temperature in the surrounding medium. For this reason methyl chlorid has been used for refrigerating purposes. Halogen Derivatives of the Paraffins. 71 Di-halogen Derivatives. 68. Di-halogen derivatives may readily be made from the tri- halogen derivatives, as is indicated by the following typical reaction : CHI3 + HI = CH2I2 + I2 Iodoform Methylene io did This reaction illustrates retrogressive substitution. The change is the reverse of the progressive substitution described on page 69. A few important di-halogen derivatives are named below : Di-halogen Derivatives of the Lower Paraffins. CnH2nR2. Methylene chlorid (Ethylene chlorid) Ethylidene chlorid Formula CH2C12 (C2H4C12)... C2H4C12 Boiling Point 41° C. 84 58 Methylene bromid CH2Br2 81 (Ethylene bromid) (C2H4Br2)... 131 Ethylidene bromid C2H4Br2 110 Methylene iodid CH2I2 182 Melting Point (Ethylene iodid) (C2HJ2) .... 81 Ethylidene iodid c2hj2 178 The second and third members of each of the above groups are typical metameric isomers. One may be made by treating ethane, C2H6, with chlorin, and is called ethylidene chlorid. The other is made by treating ethylene, C2H4 (24), with chlorin and is called ethylene chlorid. The former is a true substitution product, the lat- ter is an addition product.* Their mutual relationship is indicated by the following reactions showing their formulas and methods for their production : (JHO CH3 Ethyl aldehyde + PC13 = Phosphorus penta-chlorid chci2 ch3 Ethylidene chlorid + POC13 Phosphorus oxy-chlorid ch2 Ethylene + Cl2 = Chlorin CH2C1 I CH2C1 Ethylene chlorid The difference between these isomeric chlorids depends upon the facts that in ethylidene chlorid the two chlorin atoms are united to *The addition product is possible in the case of ethylene because the latter is an unsaturated hydrocarbon (17). 72 Chemical Notes. the same carbon atom, while in ethylene chlorid each chlorin atom is united to a different carbon atom. Tri-halogen derivatives. Two members of this group are well known compounds : Chloro- form (tri-chlor methane) and iodoform (tri-iodo methane). 69. Chloroform. CHC13. Chloroform may be made by boiling ordinary alcohol with " bleaching powder." * The reaction is com- plex, but the chlorin transforms the alcohol into chloral and the calcium decomposes the latter into chloroform (109). Chloroform may be prepared directly by boiling chloral, CC13CHO with sodium hydroxid and distilling the product (70). The reaction takes place as follows: CC13CHO + NaOH = CHC13 + NaCHO2 Chloral Chloroform Sodium formate Chloroform is a heavy, colorless, limpid liquid possessing an agreeable and penetrating odor and a sweet taste. Its specific gravity is 1.525 and its boiling point is 61° C. It is soluble in alcohol and ether, but practically insoluble in water. When poured into the latter it sinks as transparent globules. Chloroform is or- dinarily non-inflammable, but may be made to burn with a green- ish flame. It has long been used as an anaesthetic. On exposure to sunlight (47) and air, chloroform is gradually converted into free chlorin and into carbonyl chlorid, COC12, ac- cording to the following reaction : 2CHC13 + 30 = Cl2 + 2COC12 + H2O A small percentage of alcohol arrests this decomposition. The de- composition may be almost entirely prevented by keeping the chloro- form in the dark or in dark-glass vessels. The latter must be kept filled, however, to prevent access of oxygen. The presence in chloro- form of the above decomposition products may be ascertained by treat- ing the liquid with a solution of silver nitrate. White silver chlorid is formed when either of the decomposition products is present. Sil- ver nitrate fails to yield such a precipitate with pure chloroform, f * Ca(C10)2 + CaCl2 2CaOCl2 t All of the halogen derivatives of the paraffins are characterized by the fact that, although they are analogous to the haloid salts (CH3C1, KC1, NH4C1, etc.), their solutions fail to yield precipitates of silver chlorid when treated at ordinary temperature with solution of silver nitrate. They ear undissociable compounds. Halogen Derivatives of the Paraffins. 73 Chloroform containing the above decomposition products is unfit for anaesthetic purposes, because chlorin as well as carbonyl chlorid is poisonous in high degree. 70. Iodoform. CHI3. Iodoform may be made from alcohol by the action of iodin and an alkali. The process is analogous to the method, already referred to, for the preparation of chloroform. The reaction proceeds as follows : C2H5- Alcohol -OH+4I2+6KOH =chi3+ lodoform kcho2 Potassium formate ,+ 5KI+5H2O Iodoform is a crystalline solid. It forms small, lemon-yellow hexagonal plates or star-shaped crystals. It has a strong, persist- ent, saffron-like odor. It melts at 119° C. and sublimates. It is soluble in alcohol and ether; insoluble in water. Iodoform has been very generally employed as an antiseptic dressing to wounds. Tetra-halogen Derivatives. 71. Tetra-chlor methane (carbon tetra-chlorid), CC14, is the leading derivative in this group and may be made by treating car- bon di-sulfid with sulfur chlorid in the presence of a little metallic iron, which acts as a " chlorin carrier " (47) : CS2 + 2S2C12 = CC14 + 6S Tetra-chlor methane is a fragrant, colorless liquid. Its odor re- sembles that of chloroform. Its specific gravity is 1.631 at 0° C. At - 30° C. it solidifies to a crystalline mass. It boils at 76° C. It is largely used as a solvent for many substances. It does not decompose in sunlight like chloroform. Synthetic Processes in Which Halogen Derivatives Are Used. 72. The halogen derivatives of the paraffins afford the starting points for the production of many other derivatives (78). The halogen derivatives are especially important for that reason. Halo- gen derivatives also frequently occur as the intermediate products of synthetic or analytic operations. The following series of reactions, in which methyl iodid (iodo- methane) represents the halogen derivatives of the paraffins, illus- 74 Chemical Notes. trates important methods of synthesis by which alcohols, amins and other derivatives are made. [Cohen.] 1. By the reducing action of the zinc-coppcr couple (46), the cor- responding paraffin is formed (55): CH3I + H2 = CH4 + HI Methane 2. Sodium or zinc yields the next higher homologue (55) : 2CH3I + Zn = c2h6 Ethane 4- Znl2 3. A similar reaction, but with excess of zinc, yields zinc methyl: 2CH3I + 2Zn = Zn(CH3)2 Zinc methyl + Znl2 4. Water in the presence of a metallic oxid (KOH, Ag2O, PbO, K2CO3, etc.), gives the corresponding alcohol (78) : CH3I 4- KOH = ch3oh + Methyl alcohol KI 5. Alcoholic potash (a solution of caustic potash in alcohol) re- moves a molecule of hydriodic acid. A hydrocarbon is formed with two atoms less hydrogen than the corresponding paraffin : C,H J* + KOH 2 a 1 = c2h4 + Ethylene KI + H2O 6. Alcoholic ammonia forms the corresponding amin: ch3i + nh3= CH3NH2 Methyl amin + HI 7. Potassium cyanid gives the corresponding cyanid (123): CH3I + KCN = ch3cn + Methyl cyanid KI 8. Silver nitrite forms the corresponding nitro-derivative: CH3I + AgNO2 = ch3no2 + Nitro-methane Agl * Iodo-ethane is used to illustrate this particular reaction because the reaction with iodo-methane is the only exception to the rule. The theoretical methylene (CHa) which might be expected to form, is unknown. Instead of methylene, methyl ether, (CH3)2O, is formed (2CH2 -f- H2O). Halogen Derivatives of the Paraffins. 75 9. Potassium hydrosulfid yields the corresponding mercaptan; CH3I + KSH = CH3SH Methyl mercaptan + KI Relation Between a Paraffin and its Halogen Derivatives. 73. The relation between a paraffin and its halogen derivatives has already been indicated (65), but may be seen at a glance in the following formulas of ethane and its six chlorin derivatives, which serve merely as examples : Paraffin CLH Z 6 Halogen derivatives tri- tetra- c2h3ci3 c2h2ci. mono- C2H5C1 di- C2H4C12 penta- hexa- c2hci5 c2cl CHAPTER V. OXYGEN DERIVATIVES OF THE PARAFFINS. I. ALCOHOLS. Mono-hydric * Alcohols. 74. Relation to the Paraffins. The alcohols are among the most important oxygen derivatives of the paraffins. They contain hy- droxyl radicals united to carbon atoms, thus, >-C-OH. The general formula of the simplest (mono-hydric) alcohols of the par- affin division is C H2n+2O, i. e, empirically each is a paraffin plus one atom of oxygen. These relations are indicated by the following sample formulas : Paraffin ch4 c2h6 C3H8 Corresponding Mono-hydric Alcohol ch4o c2h6o c3h8o The above statements would lead to the inference that the alco- hols are addition products (65). This is not the case, however. Instead of being simply hydrocarbons plus oxygen, the alcohols consist of hydrocarbons in which hydrogen has been replaced by hydroxyl, i. e., the alcohols are hydroxids of the hydrocarbon radi- cals, thus (79) : Alcohol Paraffin ch4 C2H6 Empirical formula ch4o c2h6o Constitutional formula CH3-OH C2H5-OH These alcohols are named after the hydrocarbon radicals con- tained in them, i. e., methyl, ethyl, etc. (See footnote, page 57.) 75. Alcohol series. A list of the more important mono-hydric alcohols of the paraffin series is given on the opposite page. 76. Nomenclature. Alcohols with straight chains are called nor- mal alcohols, i. e., they are derivatives of normal paraffins (p. 66). Alcohols with branched chains are termed iso-alcohols - they are derivatives of iso-paraffins (p. 66). Some of the names in the group of alcohols listed on the opposite page contain the word " carbinol." The carbon group which con- * Mono-hydric is equivalent empirically to mon-oxy (74). 76 Alcohols. 77 Paraffin Mono-hydric Alcohols. Cn^npaO or CnH2n+iOH. Name. Formula. Boiling Point at 760 mm. Specific Gravity at 0° C. Methyl alcohol CH3-OH 66°C. 0.812 Ethyl alcohol C2H5-OH 78 0.806 Propyl alcohols Primary C3H7-OH CH3-CH2-CH2-OH 97 0.804 Secondary (Iso-propyl).... ch3K >CH-OH 81 0.789 Butyl alcohols Normal primary CH/ C^Hg OH CH3-CH2-CH2-CHa-OH 117 0.810 Normal secondary CH3-CH2K >CH-OH 100 - Primary iso-butyl. CH/ CH3V >CH-CH2-OH 107 0.806 Tertiary CH/ ch3X CH/C-OH 83 0.786 Pentyl (amyl) alcohols (20).. Normal primary ch3/ c5hu-oh CH-CH2-CH2-CH,-CH2-OH 138 0.815 Iso-butyl carbinol ch3V >CH-CH2-CH2-OH 131 0.810 Secondary butyl carbinol CH/ ch3X >CH-CH2-OH 128 (76) Tertiary butyl carbinol ch/ ch3 ch3 >c-ch2-oh Methyl propyl carbinol ch3 ch3-ch2-ch2X >CH-OH 119 Methyl iso-propyl carbinol ch/ CH3k /CH x ch/ >ch-oh 112 Di-ethyl carbinol ch/ ch3-ch2X /cH-OH 117 Di-methyl ethyl carbinol... ch3-ch/ CH3\ ch3 /c-oh 102 Hexyl alcohols Normal c2h/ C6H13-OH CH3-(CH2)4-ch2-oh 157 Melting Pinacolvl (CH/^C. >CH -OH 120 Point. 4° Heptyl alcohols Normal ch/ C7H15-OH CH3-(CH2 )5-ch2 -oh 175 Penta-methyl ethyl (CH3)3=Cx >CH-OH 131 17 Normal octyl alcohol (CH3)2Z C8Hu-OH 199 - Cetyl alcohol £16^33 OH 340 50 Ceryl alcohol ^27^55-CH - 79 Melissyl alcohol ^30^61 - 85 78 Chemical Notes. tains the hydroxyl radical is termed the carbinol group. The radi- cals attached to this group are then named as a prefix to the word carbinol. This nomenclature is applied especially to isomeric alco- hols, such as the pentyl alcohols. 77. Classification. Alcohols may be divided into primary, secondary and tertiary alcohols. In a primary alcohol the OH radical is linked to a terminal carbon atom of the chain. Such a terminal carbon atom is united to only one other carbon atom. A primary alcohol contains the mono-valent group, - CH2OH. In a secondary alcohol the OH radical is linked to an inter- mediate carbon atom in union with two other carbon atoms. A secondary alcohol contains the di-valent group, =CHOH. In a tertiary alcohol, the OH radical is linked to an inter- mediate carbon atom in union with three other carbon atoms. A tertiary alcohol contains the tri-valent group, = COH. These differences are shown in the following summary, in which R stands for any hydrocarbon radical: Primary alcohol, R -CH2OH Secondary alcohol, R2 = CHOH Tertiary alcohol, R3 = COH [Each of these three alcohol radicals is a carbinol group (76).] Examples of these three classes of alcohols may be found in the table on page 77, and in the formulas below. All the mono-hydric alcohols may be regarded as derivatives of methyl alcohol (carbinol, p. 83), as is indicated by the following typical formulas : a. Primary alcohols. Alcohols. 79 78. Synthesis. There are many methods by which alcohols may be made (82). One of the simplest methods consists of the transformation of a halogen derivative (72) by an exchange of hydroxyl for halogen. This method shows the relation between the hydrocarbon and the alcohol. The reaction may be carried out as follows (72) : c2h5i + Ethyl iodid NaOH = c2h5oh + Ethyl alcohol Nai 79. Constitution. We have already stated that the alcohols are hydrocarbon hydroxids. The above reaction gives conclusive proof of this fact. In some reactions the alcohols resemble water, in others they are similar to such hydroxids as caustic soda. Relation between alcohol and water. The relation between the alcohols and water may be shown by the following typical reactions: 1. Action of sodium: Water: 2HOH + 2Na = 2NaOH Sodium hydroxid + H2 Alcohol: 2C2H5OH + 2Na = 2NaOC2H6 + Sodium ethylate H2 Further treatment of the sodium ethylate with sodium is without effect. It is obvious, therefore, that one of the six hydrogen atoms in the above alcohol bears a different relation to the molecule than the other five. It is evidently the one that is linked to the oxygen atom. 2. Action of phosphorus chlorids (99) : Water HOH + PC15 =HC1+HC1 + POC13 Alcohol C2H5OH + PC15 = C2H5CI + HC1 + POC13 Ethyl chlorid 3HOH + PC13 = 3HC1 + P(OH)3 3C2H5OH + PC13=3C2H5C1 +P(OH)3 In each of the reactions under 1 and 2 the methyl radical plays the part of a hydrogen atom. The correspondence existing between the alcohols and water is further emphasized by the fact that some of the alcohols combine with certain crystalline inorganic salts in a relation analogous to that of water as water of crystallization. Crystalline calcium chlorid illustrates this relation : 80 Chemical Notes. Water of crystallization, CaCl2, 6H2O Alcohol (methyl) of crystallization, CaCl2, 4CH4O Relation between alcohol and caustic alkalies. This relation may be seen in the following reactions : 3. Action of mineral acids: Water NaOH + HC1 = NaCl + H2O Alcohol CH3OH + HC1 = CH3 -C1 + H2O Methyl chlorid NaOH + HNO3 = NaNO3 + H2O CH3OH + hno3 = ch3 - no3 + h2o Methyl nitrate NaOH + H2SO4 = NaHSO4 4-H2O CH3OH + H2SO4 = CHS - hso4 + h2o * Methyl hydrogen sulfate In each of these reactions between alcohol and acid, a methyl radi- cal takes the part played by a sodium atom in the corresponding reactions. The acid is neutralized in each case, a salt is formed and water results (81). In the above reactions atoms of hydrogen were replaced by atoms of sodium (1) ; hydroxyl groups were replaced by chlorin atoms (2, 3) and by mono-valent inorganic radicals (3), and acids were neu- tralized, with salt formation and water production (3). These facts prove that the following substances are hydroxids and are similar in constiution: H-OH Water Na-OH Sodium hydroxid CH-OH Methyl alcohol * If the alkyl hydrogen sulfates are heated, sulfuric acid separates and unsaturated hydrocarbons of the olefin series result, thus : C2H5-hso4 = c2h4 + H2SO4 Ethyl hydrogen Ethylene sulfate The olefins may be obtained directly by heating the alcohol to a fairly high tem- perature with a relatively large excess of sulfuric acid. When, however, the alcohol is in excess of the sulfuric acid, ethers (90) result as follows : "Thus, the action of sulfuric acid upon an alcohol is of a three-fold character. At the ordinary temperature the two combine to form the alkyl hydrogen sul- fate; at high temperatures, with excess of sulfuric acid, hydrocarbons (olefins) are produced ; with excess of alcohol, ethers are formed. This is one of many exam- ples which might be given of an organic reaction wherein a change in the condi- tions produces a marked alteration in the nature of the products." [Cohen.] Alcohols. 81 8o. General Physical Properties. In physical properties alcohols show a gradation corresponding to increase in their molecular weights, as is true, in general, of all homologues. The mono-hydric alcohols are colorless substances, with neither acid nor alkaline reaction to such indicators as litmus. The lower members of the series, such as common alcohol (C2H5-OH), are colorless liquids; the higher members, such as cetyl alcohol (C1GH33-OH), are waxy solids. Solubility in water gradually decreases as the carbon content increases (56). The lower alco- hols are volatile and have a characteristic odor and a burning taste. The higher alcohols are non-volatile, resemble fat, and are odorless and tasteless. Common (ethyl) alcohol is a valuable solvent. Tinctures are alcoholic solutions of various drugs and other substances. We have already alluded to the resemblance between water and the mono-hydric alcohols (7 9). 8i. Chemical transformations. I. Alcoholates. The hy- drogen of the hydroxyl group may be replaced by metals, forming alcoholates, as follows (7 9): 2C2H5-OH + 2Na = 2NaOC2H5 + H2 Ethyl alcohol Sodium ethylate (Sodium alcoholate) II. Esters. When an acid reacts with an alcohol, the acid is wholly or partly neutralized, and a salt is formed (79) : CJL-OH + HNO, = C2H.--NO, + H2O 4 O o A O O it Ethyl alcohol Ethyl nitrate In this reaction the alcohol plays the part of a base, the alkyl being equivalent to an atom of a metal, such as potassium in KOH. The haloid salts (65) are made very readily by treating the alcohols with phosphorus haloids (79). The paraffins may be made with ease from the haloid salts, as has already been indicated (55). III. Oxidation products of primary, secondary and tertiary alcohols. On oxidation, these types of alcohols yield the following products : A. Primary alcohols yield, in two stages of oxidation, aldehydes (97) and acids (97) having the same carbon contents, as follows : 82 Chemical Notes. ch3 0^3 (a) H-C-OH + O = H-C=0 + H20 H Ethyl alcohol Acetaldehyde w ?H3 +°= F3 H-C-O HO-C=O Acetic acid B. A secondary alcohol yields a ketone (97) of like carbon content in the first stage of oxidation and an acid of less carbon content in the second stage, as follows : ch3 ch3 (a) H-C-OH + O = C=O + H2O CH3 ch3 Iso-propyl alcohol Di-methyl ketone ch3 ch3 (5) C=O + 2O2 = HO-0=0 + C02 + H20 CH3 Di-methyl ketone Acetic acid C. Tertiary alcohols yield, in two stages of oxidation, ketones and acids of less carbon contents, as follows : ch3 0h3 (a) CH3-0-OH + 2O2 = 0=0 + CO2 + H2O ch3 ch3 Tertiary butyl alcohol Di-methyl ketone (6) On further oxidation, di-methyl ketone yields the products indicated under B, b above. 82. Sources. Natural sources. Alcohols occur naturally in plants and animals, especially as constituents of oils, fats and waxes. Very small quantities of common alcohol are normally produced in various parts of the animal body. The lower mono- hydric alcohols are conspicuous products of fermentation. Fermentation. When yeast is added to a sugar solution, the mixture soon appears to be boiling gently and froth collects at the top, although there is hardly any change in temperature. This process is called fermentation. The yeast produces ferments which change the sugar, by hydration and cleavage, into alcohol and carbon dioxid, as follows : Alcohols. 83 (1) c12h22ou + h2o = c6h]0o6 + c6h12o6 Cane sugar Grape sugar Fruit sugar (2) C6H]2O6 = 2C2H5-OH + 2CO2 The alcohol may be obtained, from a fermented mixture, by dis- tillation. Small quantities of higher alcohols, such as iso-butyl alcohol, accompany the common alcohol in both the fermentation process and the distillation of the mixture (83). Distilled liquors are obtained by the distillation of fermented mixtures of various kinds, e. g., whisky from fermented rye or corn, rum from fermented molasses. The different flavors of such liquors are due chiefly to the volatile products accompanying the alcohol. Wines result from the natural fermentation of grape juice. Beer is made by changing the starch in germinated barley (malt) to sugar in a preliminary fermentative process. The soluble portion of the extract of the malt (mash), containing the barley sugar, is mixed with hops, and the mixture is boiled. The clear supernatant fluid is then treated with yeast, with ultimate fermentation into beer. The taste of the beer is due chiefly to substances dissolved from the hops. The proportion of alcohol in such beer would be relatively small, but it is usually increased by an addition of sugar (glucose) just before the treatment with yeast. Artificial sources. There are many artificial methods for the production of alcohols. We have already seen that aldehydes and ketones are formed by the oxidation of alcohols (81). On revers- ing the process, i. e., by reducing the former substances, alcohols result, as in the following typical reaction : CH„-CO-CH„ + H2 = CH„-CHOH-CH„ Di-methyl ketone Secondary propyl alcohol Esters may be made from alcohols as has already been stated (81). Alcohols may be made from the esters by treatment with excess of water for the reason that the following typical reaction is reversible : CH OH + HC1 zZ CH,Cl + H2O Synthesis from halogen derivatives was referred to on page 79. 83. Typical mono-hydric alcohols. Methyl alcohol (wood alco- hol, carbinol'), CH3-OH [H-CH2OH]. When wood is subjected to " dry " (destructive) distillation, inflammable gases are formed, 84 Chemical Notes. a strongly acid aqueous distillate is obtained, a quantity of tar is produced, and a black residue, charcoal, remains. The aqueous dis- tillate is known as pyroligneous acid or wood vinegar, and is a mix- ture consisting of methyl alcohol, methyl aldehyde (108), acetone (114), acetic acid (136), and other organic compounds. Methyl alcohol is also produced by the destructive distillation of by-products in the sugar industry, such as molasses. Commercial methyl alcohol usually contains variable quantities of methyl aldehyde, acetone, etc. Pure methyl alcohol is a colorless liquid that boils at 66-67° C, At 20° C. its specific gravity is 0.812. It has a strong, unpleasant odor. It mixes readily with water, common alcohol and ether. It closely resembles ordinary alcohol in all its properties. It burns with non-luminous flame. It is more poisonous than common alco- hol. Methyl alcohol is frequently used to adulterate alcoholic bev- erages. It is extensively used as a solvent of organic compounds, especially for dissolving shellac and resins in the preparation of varnishes, etc. Ethyl alcohol (spirits of wine), C2H5-OH, [CH3- CH2OH]. Ethyl alcohol, or ordinary alcohol, is the best known mono-hydric alcohol. It occurs naturally in some plants and in many animals in small quantities. It is prepared on a technical scale almost en- tirely by the fermentation of liquids containing sugar, with subse- quent distillation (82). Ordinary commercial alcohol contains variable quantities of water, fusel oil and other substances such as aldehyde (97). Fusel oil is the name given to the mixture of propyl, butyl, pentyl (amyl) and hexyl alcohols, which is formed with the ethyl alcohol in the fermentation of sugar. Fusel oil is more poisonous than ethyl alcohol. Pure ethyl alcohol f absolute alcohol ") is a colorless liquid with an agreeable odor. It boils at 78° C. Its specific gravity at 0° C. is 0.806. At - 130° C. it solidifies to a snow-white mass. It burns with non-luminous flame, and is frequently used for heating pur- poses because it burns without depositing soot. Its poisonous action on organisms is well known.* This alcohol is one of the * Beer contains about 3 to 5 per cent, of ethyl alcohol. Wines contain from about 8 to 15 per cent. Whisky, brandy and other distilled liquors may contain 50 per cent, or more. Alcohols. 85 most general solvents of an organic character, just as water is the principal inorganic solvent. Ethyl alcohol is therefore extensively used in the arts. Tinctures are solutions in ethyl alcohol. II. Poly-hydric Alcohols. 84. Thus far in this chapter we have considered only the mono- hydric alcohols. In the mono-hydric alcohols one hydrogen atom attached to a carbon atom of the original hydrocarbon has been replaced by a hydroxyl radical. These alcohols are the simplest alcohols, just as mono-hydric (mon-acid*) hydroxids, such as po- tassium hydroxid, are the simplest hydroxids. Among the inorganic hydroxids there are poly-hydric (poly-acid) compounds, such as barium hydroxid, Ba(OH)2, and aluminium hydroxid, A1(OH)3, the number of hydroxyl radicals in these hydroxids depending on the valences of the positive atoms. The hydrocarbons likewise form poly-hydric derivatives, the maximum number of hydroxyl radicals in each alcohol being de- termined by the number of carbon atoms in the hydrocarbon from which the alcohol may be regarded as having been derived. There are no poly-hydric alcohols in which more than one hy- droxyl radical is attached to a single carbon atom. Whenever the formation of poly-hydroxyl derivatives of that type might be ex- pected, such for example as might be expressed by the general formula, then, as a rule, water separates and an anhydrid results,! as is indi- * The acidity of a hydroxid, it will be recalled, is determined by the number of its hydroxyls. Each hydroxyl may unite with a hydrogen atom, from an acid, to form water. Hydroxide are, therefore, mon-acid or poly-acid (mono-hydric or poly-hydric), according to the number of hydroxyl radicals in them. t Under ordinary conditions, the carbon atom is unable to hold more than one - OH group. For this reason carbonic acid, cannot exist; it breaks up instantly into CO2 and H2O. Chloralhydrat, is one of the few exceptions (109) to the rule just indicated. 86 Chemical Notes. cated in the following reactions (99) : The following formulas of representative compounds indicate the relationships among the more important types of mono- and poly-hydric alcohols : Alcohols. 87 Relations Between a Typical Paraffin and Its Halogen and Alcohol Derivatives. 85. The relations existing between a typical paraffin and the general types of derivatives thus far considered are shown by the formulas given below: Paraffin Derivatives Halogen Alcohol Mono-halogen Poly-halogen Mono-hydric Poly-hydric c2h6 c2h5-ci c2h4 = ci2 C2H5-OH C2H4 = (OH)2 The mono-hydric alcohol groups may be summarized as follows, letting R stand for any alkyl radical: Primary alcohol, R - CH2OH Secondary alcohol, R2 =CHOH Tertiary alcohol, R3 = COH CHAPTER VI. OXYGEN DERIVATIVES OF THE PARAFFINS. II. ETHERS. Relation to the Paraffins and Alcohols. 86. Ethers may be regarded as the oxids of mono-valent paraffin radicals or of alcohol radicals. The relations of the alcohols and the ethers to each other and to the paraffins may be seen from the following formulas : Paraffin Alcohol Ether General formulas : CH,, C H , O CHO 71 r u 71 Z71 1 a 71 aTIu Simplest members : CH4 CH3-OH (CH3)2=O Methane Methyl Di-methyl alcohol ether Although ethers and alcohols have the same general formula, they are quite different in their structure and properties. We have already learned that the alcohols are comparable to the metallic hydroxids (79). The ethers may be regarded as analogous to the metallic oxids. These statements are illustrated by the following formulas: These facts make it evident that the ethers may be regarded as anhydrids of the alcohols, as is shown in the following actual reaction (90) : C TT \ 2C2H OH -H2O = *5>O O2H/ Ethyl alcohol Ethyl ether For this reason the ethers may be considered as direct derivatives of the alcohols. 88 Ethers. 89 87. Ethers are of two general types. In one type the two alcohol radicals are of the same kind. Such ethers are called simple ethers. In a second type the two alcohol radicals are different. Such ethers are called mixed ethers.* The following formulas illustrate these types : Classification. Simple Ethers. 88. The subjoined table gives a list of the more important simple ethers : Paraffin Simple Ethers, f CnH2n+2O. Name. Formula. Boiling Point at 760° mm. Specific Gravity. Methyl ether (CH3)2 = 0 CH3\ >0 CH/ -24° C. - Ethyl ether (C2H5)2 = O ch3-CH2\ /O ch3-ch/ 35 0.731 (4° C) Propyl ether (C3H7)2 = O ch3-(ch2)2\ CH3-(CH2)/° 91 0.763 (0) Iso-propyl ether (C3H7)2 = O (CH3)2 = CHx (ch3)2=ch/° 69 0.743 (0) Normal butyl ether (CtH#)2 = O. CH3-(CH2)3\ ch3- (CH2)/° 141 0.784 (0) Iso-butyl ether (C4H9)2 = O (CH3)2 = CH-CH^ (ch3)2=ch-ch/° 122 0.762 (15) Iso-pentyl ether (C8Hn)2 = O (CH3)2= ch-(ch2)2\ (CH8)2 = CH-(CH2)/° 173 0.781 (15) Heptyl ether (C7H18)2 -0 CH3-(CH2)6\ >0 CH3-(CH2)/ 262 0.815 (0) Octyl ether (C8H17)2=O ch3-(CH2),x CH3-(CH2)/° 281 0.805 (17) Cetyl ether (C16H33)2 -0 ch3- (CH2)15X >0 CH3-(CH2)j/ Melting Point 55 - * 11 Compound ethers" or esters consist of an alcohol radical and an acid radical com- C TT \ bined with oxygen, as ^2q 5^>O, ethyl nitric ester. See page 81. f Isomerism among the ethers depends upon the homology of the alcohol radicals. 90 Chemical Notes. Mixed Ethers. 89. The subjoined table gives a list of some of the more impor- tant mixed ethers : Paraffin Mixed Ethers, CnlL^O. Name. Formula. Boiling Point at 760° mm. Specific Gravity. Methyl ethyl ether CH3\ >0 11° 0.725 (0° C.) 0.745 (0) 0.777 (0) 0.759 (21) Ethyl propyl ether c2h/ c2h5X >0 64 Propyl butyl ether c3h/ c3h7X >0 117 Ethyl pentyl ether C.H/ c2h5 x \o 103 Ethyl hexyl ether C5Hn/ C2H5 . V> 135 Pentyl heptyl ether c6h13/ C5Hh\ 220 0.608 (20) 0.801 (0) Methyl octyl ether c7h15/ CHS x >0 173 Ethyl cetyl ether CgH17 C2H5 . Melting Point 20 / Methods of Preparation. 90. Among the methods of ether production, the following are the most important: 1. When an alcohol is treated with a metallic hydroxid, the hydrogen atom of the hydroxyl is exchanged for a metallic atom, and an alcoholate and water result, thus (81): CH3OH + NaOH = CH3ONa + H2O Sodium methylate If an alcoholate is treated with a mono-halogen paraffin derivative, a reaction such as the following takes place : CH3ONa + CHJ = C2H6O + Nai Methyl ether This reaction determines definitely the structure of the ether, for the latter is obtained from the alcoholate by replacing the sodium Ethers. 91 atom with a methyl radical. Therefore, the formula for the ether must evidently be written (91), 2. Ethers may be prepared by the action of paraffin halogen derivatives on metallic oxids, as follows : This reaction also shows clearly the constitution of the ethers. 3. The most important method of formation depends upon the reaction between sulfuric acid and alcohols. Two distinct changes are involved in this reaction. The initial product is an alkyl hy- drogen sulfate; the final product is an ether. Simple as well as mixed ethers may be made in this way. The following reactions illustrate these statements (79): Mixed ether. Certain other acids, such as phosphoric, arsenic and boric, behave like sulfuric acid in this respect. It should be noted that in the above reactions none of the sul- furic acid is lost; it merely undergoes temporary transformation. Only the alcohol suffers permanent change. For this reason a small quantity of sulfuric acid can convert a very large amount of alcohol. The action of the sulfuric acid is in effect a dehydration, two molecules of the alcohol losing a molecule of water (86): 92 Chemical Notes. Constitution. 91. We have seen that the ethers are alkyl oxids. Inquiring more closely into the structure of the ethers, we observe the detailed configuration from the following reaction (90) : This ether formula may also be written as follows : In each of these formulas the characteristic group =C-0-C = is obviously present. Transformations. 92. Ethers are chemically very indifferent because all the hydro- gen in them is united directly to carbon. Thus, metallic sodium, in the cold, has no effect on them (79). When oxidized they yield the same products as those obtained from the corresponding alcohols. They yield esters (81) when heated with concentrated sulfuric acid. Phosphorous penta-chlorid, at 180° C., converts them into mono- halogen derivatives, as follows (79) : The haloid acids have the same effect at high temperatures. Hy- driodic acid, for example, produces in the cold an alcohol and a mono-halogen derivative, as follows : General Physical Properties. 93» Ethers, like the alcohols, are colorless and neutral. They are much more volatile than the corresponding alcohols. Ethers are lighter than water and much less soluble in water than the alcohols. Ethers. 93 The lowest ethers are gases or very volatile liquids. The inter- mediate ethers are liquids. The highest, e. g., cetyl ether, are solids. The boiling points of the ethers are much lower than those of the corresponding alcohols. Ethyl Ether. C H \ The ether of most importance is common (di-ethyl) ether, /At/O. 94. Preparation. Ordinary ether is usually made from com- mon alcohol by the sulfuric acid process already referred to (90). For this reason common ether is frequently called sulfuric ether. * 95. Properties. Ethyl ether is a limpid liquid with peculiar odor, burning taste and markedly anaesthetic effect. It is one of the best general anaesthetics. Its specific gravity is 0.731 at 4° C. It boils at 35° C., and evaporates very rapidly, with marked cool- ing effect, even at ordinary temperature. The low temperature produced by ether in its evaporation is a property which makes this substance valuable for refrigerating purposes. Employed in the form of spray, it produces local insensibility. Ether solidifies to a crystalline mass at - 129° C. Ether is very inflammable, burning with a luminous flame. Its vapor is relatively heavy and forms explosive mixtures with air. It is comparatively insoluble in water; but miscible in all proportions with alcohol. When ether is shaken with water the two liquids quickly separate into distinct layers; ether, because of its lower specific gravity, collects at the top. Most of the organic substances that are insoluble in water, such as fats, are soluble in ether. Ether is a valuable solvent, therefore, and is very generally used for the extraction of organic substances from liquid and solid mixtures. Relations Between a Typical Paraffin and Its Mono- halogen, Mono-hydric (Primary) Alcohol and Ether Derivatives. 96. The general relations existing between a typical paraffin and the types of its derivatives thus far considered are shown by the representative formulas given below : Paraffin Derivatives Halogen Alcohol Ether CH4 CH,-Cl CH,-OH ^3>o CH3 * Esters are frequently called "compound ethers." Thus ethyl acetate CH3COO-C2H5, is known as acetic ether (87). CHAPTER VII. OXYGEN DERIVATIVES OF THE PARAFFINS. III. ALDE- HYDES AND KETONES. Common Characteristics of Aldehydes and Ketones. 97. Relation of aldehydes and ketones to the alcohols. When a paraffin such as methane is completely oxidized, carbon di-oxid and water are the final products, as follows : CH4 + 2O2 = CO2 + 2H2O Between the paraffin and these final combustion products there are a number of very important oxidation substances. We have already noted the fact that the empirical formula of methyl alcohol, a typical mono-hydric alcohol, is CH4O (74). Compared with the formula of methane, CH4, this alcohol might be regarded as methane plus one atom of oxygen, i. e., as a simple oxid. It has been shown, however, that the oxygen exists in the alcohol in direct combination with a hydrogen atom to form the hydroxyl group, and that the alcohol is a hydroxid comparable to hydrogen oxid (water), as the formulas below indicate (79): Methane, CH4 Methyl alcohol, CH4O, or CH3-OH Water, H2O, or H - OH The mono-hydric alcohols are readily dehydrated as we have seen (86), and ethers result. These alcohols are also readily oxidized and in their oxidation aldehydes, ketones and acids result, according to the nature of the alcohols and the extent of the oxidation (81). We have learned that mono-hydric alcohols occur in three gen- eral types : Primary, secondary and tertiary alcohols, with the following characteristic groups (77). Primary, R -CH2OH Secondary, R2 =CHOH Tertiary, R3 = COH 94 Aldehydes and Ketones. 95 Aldehydes result from the oxidation of primary alcohols. Ketones are formed in the oxidation of secondary and tertiary alcohols (77). 98. Homologous series-Aldehydes and Ketones. Tables of the more important aldehydes and ketones are given below and on page 96. 99. Constitution of the Aldehydes and Ketones. The alde- hydes and ketones have the same general formula, C?H2nO. The primary, secondary and tertiary alcohols have the general formula, CwII2n+2O. It is obvious, therefore, that in the formation of aide- Paraffin Aldehydes,* CjJLnO. Name. Formula. Melting Point. Boiling Point at 760 mm. Formaldehyde H-CHOf - -21° C. Acetaldehyde CH3-CHO -121° C. 21 Propaldehyde CH3-CH2-CHO - 49 Butyraldehyde CH3-(CH2)2-CHO - 75 Iso-butyraldehyde ch3. >CH-CHO CH/ - 63 Valeraldehyde CH3-(CH2)3-CHO ch3X - 103 Iso-valeraldehyde >CH-CH2-CHO ch/ - 92 Capronaldehyde ch3-(CH2\-cho - 128 CEnanthyl aldehyde CH3-(CH2)5-CHO - 155 Capric aldehyde C9H19-CHO - (106H Lauric aldehyde CnH,3-CHO 45 (142) Myristic aldehyde C13H27-CHO 53 (168) Palmitic aldehyde C15H31--CHO 59 (192) Stearic aldehyde C„H35-CHO 64 (212) hydes and ketones from alcohols, the latter lose, in each case, two atoms of hydrogen, thus : § c h2 . 2O n 2n±2 Alcohol + o = C H, O + n 2n Aldehyde or ketone h2o " In this oxidation an oxygen atom pushes itself between a hydrogen atom and the carbon atom to which the hydroxyl group is attached. At the moment of formation, the expected di-hydric * A number of the less conspicuous homologues are omitted. t The CHO radical is written constitutionally as follows : /C^q ($9). t The figures in parenthesis refer to boiling points determined under diminished pressure. That for capric aldehyde was obtained at 15 mm. pressure. For the rest the pressure was 22 mm. 3 The oxidation results in the withdrawal of two hydrogen atoms to form water, H2 + o = h2o 96 Chemical Notes. Paraffin Ketones,* CnH2?lO. Simple ketones.f Name. Formula. Melting Point. Boiling Point at 760 mm. Pressure. Acetone (CHA..-CO -95° C. 57° C. Propione (C2H5)2=CO 103 Butyrone (C3H7)2=CO - 144 Iso-butyrone rcn3X "i > CH 2-CO 124 ch/ rcn i Iso-valerone >ch-ch2 3- co 182 _ch/ J Caprone (C5HU)2=CO 15 226 Tetra-ethyl acetone r^H5X 3 >CH 2-CO 203 _c2h/ _ (Enanthone (CJLA,-CO 30 263 Caprylone (C7H16)2=CO 40 Caprinone (CrH„)9-CO 48 Laurone (C„H,A,-CO 69 Myristone (C13H27)2-co 76 - Palmitone (O-H...),-co 83 ■ ■ . Stearone (CnH^),-CO 88 Mixed ketones.f Methyl ethyl ketone CH-CO-C,H5j - 81 Methyl propyl ketone CH3-CO-C3H7 - 102 Methyl hexyl ketone ch3-co-c6h13 - 171 Methyl nonyl ketone ch3-co-c9h19 15 225 Methyl palmityl ketone ch3-co-c15h31 48 (244)§ Methyl stearyl ketone ch3-co-c17h35 55 (265) alcohol throws off water, and its anhydrid results (84), i. e., an aldehyde or ketone: * A few homologues are omitted. t Ketones are simple or mixed, as in the case of ethers (87), when their alkyl radicals are alike or different, respectively. J Each of the formulas may also be written as above, § The figures enclosed in parenthesis were determined at reduced pressure-at 100 mm. Aldehydes and Ketones. 97 By further oxidation both aldehydes and ketones become acids (116)-the hydrids of the acid radicals. The ketones are more readily decomposed into CO2 and H2O (99). Conversely, alde- hydes and ketones again become primary and secondary alcohols on addition of hydrogen : H CH-C=0 + H2 = CH-CH-OH Acetaldehyde Ethyl alcohol CTT CTT ',,>C=O + H2 = 3>CH-OH CH/ 2 VH3/ Di-methyl ketone Iso-propyl alcohol " Because the aldehydes and ketones manifest an additive power with reference to hydrogen, they may be compared with compounds containing doubly linked carbon atoms, which also, by a dissolution of their double union, can add hydrogen. Compounds of this class having in their molecules carbon atoms which are doubly (or trebly) united, are in the more restricted sense called ' unsaturated carbon derivatives ' (17). This idea may be extended, and all carbon deriv- atives having atoms of other elements in double or treble union with carbon, may be considered as 'unsaturated.' From this stand- point the aldehydes and ketones are unsaturated bodies (102) and in fact most of the reactions of these two classes of substances are due to the additive power of the unsaturated = C0 radical." [Richter.] It is evident from the foregoing facts that aldehydes and ketones contain the =C0 radical. This radical is called carbonyl. An aldehyde consists of a carbonyl radical in union with one atom of hydrogen and one alkyl group. A ketone consists of a carbonyl radical combined with two alkyl groups, thus : $/CO, or R -CHO Aldehyde ®>CO,orB2=CO Ketone In these formulas R stands for any alkyl group. That the aldehydes and ketones do not contain hydroxyl radicals is shown by the fact that when they are treated with such a re- agent as phosphorus penta-chlorid, hydrogen is not removed from them. Under similar conditions there is a removal of hydroxyl from alcohols (79). 98 Chemical Notes. The following reactions make these statements clear: Alcohol: CH3-OH +PC15 = CH3-C1+HC1 +POC13 Methyl alcohol Mono-chlor methane Aldehyde : CH3-CHO + PC15 = CH3-CHC12 + POC13 Acetaldehyde Di-chlor ethane Ketone : ™3/CO + PCL = /CC12 + POC13 V/_LJLr> \_y-LjL3 Di-methyl ketone Di-chlor propane These reactions further emphasize the fact that aldehydes and ketones are carbonyl ( = CO) compounds.* * " To understand the action of phosphorus penta-chlorid on aldehydes and ketones, let us consider briefly the action of this reagent in general upon com- pounds containing oxygen. When it is brought in contact with water, the first change is represented by the equation H2O + PC15 = POC13 + 2HC1 Next, the oxy-chlorid, POC13, is acted upon thus : 3 H2O + POCI3 = PO(OH)3 + 3 HC1 Or, expressing both changes in one equation, we have The phosphorus penta-chlorid gives up its chlorin and takes up oxygen, or oxygen and hydrogen, in its place. This is the general tendency of the chlorids of phosphorus. "Now, when a chlorid of phosphorus is brought together with an alcohol, the oxygen is replaced by chlorin, two atoms of the latter for one of the former, thus : 4 H2O + PCI5 = PO(OH)8 + 5 HC1 But as hydroxyl, -O-H, is uni-valent, its place cannot be taken by two atoms of chlorin and one of hydrogen, and the two chlorin atoms have not the power of linking the hydrogen to the ethyl. Hydrochloric acid is given off, and a com- pound is formed, which may be regared as alcohol in which one chlorin atom takes the place of the hydroxyl. This is the kind of action which takes place whenever a chlorid of phosphorus acts upon a compound containing hydroxyl ; and we hence make use of the reaction for determining whether hydroxyl is or is not present in a compound. "When aldehyde, for example, is treated with phosphorus penta-chlorid, the action is entirely different from that just described. Instead of a hydrogen and an oxygen atom being replaced by one chlorin atom, the oxygen atom alone is replaced by two chlorin atoms : C2H5 - OH + PCI6 = C2H5C1-C1H + POC13 C2H4O + PC15 = CaH4CI2 + POC1S If the explanation above offered of the action of phosphorus penta-chlorid on alco- hol is correct, it follows that aldehyde is not a hydroxyl compound. We can readily understand why the oxygen atom should be replaced by two chlorin atoms, if it is in combination only with carbon as in carbon monoxid, CO (57). There is an Aldehydes and Ketones. 99 Since only the primary alcohols yield aldehydes, the =CO radical must be located in aldehydes at the end of the carbon chain. Since only the secondary and tertiary alcohols yield ketones, the = CO radical must be located in ketones between the ends of the carbon chain. The facts are made plain by the following reactions: IT I. ch3-ch2-ch2oh + o = ch3-ch - + h2o Normal propyl alcohol Propaldehyde Y II. CH-c-CH3 + O = CH3-C-CH3 + H2O OH O Iso-propyl alcohol Di-methyl ketone The different results of oxidation of the aldehydes and ketones are shown in the following typical reactions (p. 96) : I. CH3-CHO + O = CH3-COOH * Acetaldehyde Acetic acid II. ™3^CO + 30 = CH,-COOH + H-COOH f UH/ d Di-methyl ketone Acetic acid Formic acid The aldehyde forms, on oxidation, an acid containing the same number of carbon atoms. The ketone yields two acids containing a smaller number of carbon atoms (110). essential difference between this kind of combination and that which we have in hydroxyl as =C-O-H. In the latter condition the oxygen serves to con- nect carbon with hydrogen ; in the former it is in combination only with the car- bon, and, presumably, the force which holds it can also hold two atoms of chlorin in addition (57) or of any other uni-valent element with which it can unite. So that, if oxygen be in a compound in the carbon mon-oxid condition, we should expect it to be replaced by two atoms of chlorin when the compound is treated with phosphorus penta-chlorid. Let R=CO represent any such compound ; then we should have : R=CO + PC15 = R=CC12 + POCI3 while, when oxygen is present in the hydroxyl condition, we have : R=C-O-H + PC15 = R=CC1 + POC13 + HC1 Just as the latter reaction is used to detect the presence of hydroxyl oxygen, so the former is used to detect oxygen in the other condition, which is commonly known as the carbonyl condition." [Remsen.] * The COOH group is present in all organic acids and is called the carbo'xyl group (116). j- Formic acid oxidizes readily and breaks down into carbon dioxid and water, thus (135) : H-COOH + O = CO2 + H2O Chemical Notes. 100 These general differences in the effects of oxidation are satisfac- torily accounted for by differences in the general formulas of the aldehydes and ketones. too. Nomenclature. The term aldehyde is derived from the latin alcohol dehydrogenatum, meaning " alcohol from which hydrogen has been removed." The term ketone is a modification of acetone, the first member of the paraffin simple ketones. The individual aldehydes usually receive names derived from the names of the acids to which they give rise on oxidation. Methyl alcohol, for example, yields an aldehyde which on oxidation is converted into formic acid. The aldehyde is known as formal- dehyde : CH- OH^ H-CHO^ H-COOH Methyl alcohol formaldehyde Formic acid The names of the individual ketones were originally derived from the names of the acids which yielded them on distillation. They are also named after the alkyl radicals linked to the carbonyl group. Thus : CH \ . . [ acetone, or ph /CO, from acetic acid, is < , ( di-methyl ketone. ioi. Methods of formation of aldehydes and ketones. The following important methods of production are common to the aldehydes and the ketones. 1. Oxidation of alcohols. Primary alcohols yield aldehydes (81); secondary and tertiary alcohols yield ketones (81). 2. Dry distillation of the barium or calcium salts of fatty acids (118)- a. When the barium salt of formic acid is distilled with the salt of another fatty acid, aldehyde results : H - COO/Ba + CH° - COO/Ba = 2CH-CHO + 2BaCO3 Barium formate Barium acetate Acetaldehyde The hydrogen of the formate furnishes the hydrogen for the /H -group in the aldehyde. Aldehydes and Ketones. 101 b. When a single salt of a fatty acid (excepting a formate) is distilled, a simple ketone results (98) : CH -COCK CH8\ CH -COO/B CH/C° + B C°3 When a mixture of two such salts (excluding a formate') is dis- tilled, mixed (98) ketones are formed : CH-COO\ C2H5-COO\ _ c2h5\ , CH-COO/B -COO/B ' 3 Barium propionate Ethyl methyl ketone 102. General chemical properties of aldehydes and ketones. The general chemical reactions of the aldehydes and ketones are due to two characteristic properties of the unstable carbonyl group, = CO, contained in each. 1. The = C0 radical readily withdraws two hydrogen atoms from the reacting substance and forms with one hydrogen atom an attached hydroxyl radical, -OH, or, 2. The oxygen of the =CO radical is withdrawn from the alde- hyde or ketone by two hydrogen atoms, from the reacting substance, to form water. The second process is intimately connected with the first, which probably always precedes it. Addition of hydrogen in the form of the -OH group, (a) Alde- hydes and ketones are converted into alcohols on reduction (99), thim • «>c=o + H2=^/C<nH Example: CH3\ za >n CH. /OH jj /Q-yields h/^Xh Acetaldehyde Ethyl alcohol CH3\n za CH3\^/OH CH/C~°' yields CH/C\H Acetone Iso-propyl alcohol (6) Aldehydes and ketones unite with hydrocyanic acid (HCN) to form cyanhydrins, thus : 5>C=O + HCN = |>c<™ * In these general formulas B. may represent a hydrogen atom, or an alkyl, or both. Chemical Notes. 102 Example: CH3k n • jj/O-O' yields -p-/ Acetaldehyde Acetaldehyde cyanhydrin CH3\ - n CH3\ /OH ch/c~o> ylelds CH/C\CN Acetone Acetone cyanhydrin Removal of oxygen in the form of xoater. a. Aldehydes and ketones unite with hydroxyl amin (H2=N-OH) to form oxims. Aldehydes yield aldoxims; ketones yield ketoxims, thus : *>C=O + H2=N-OH = ^C=N-OH 4- H2O Examples: ™3>C=O, yields OH Acetaldehyde Acetaldoxim CH^0"0' y!elds ch'/C=N-°H Acetone Acetoxim b. Hydrazin (H2N-NH2), phenyl* hydrazin (H2N-NH-C6H5) and various hydrazin derivatives combine with aldehydes and ketones to form hydrazones, phenyl hydrazones, etc., thus : |>c=o + H2N-NH-C6H5 = ^>C=N-NH-C6H5+h2o C^O; yields CH/C=N-NH-C6H5 Acetaldehyde Acetaldehyde phenyl hydrazin CH \ CH CH/C=O' yields CH/C=N-NH-CA- Acetone Acetone phenyl hydrazin * Phenyl, C6H5, bears the same relation to benzene, C6H6, as CHS to methane, CHp Aldehydes and Ketones. 103 Aldehydes. The preceding sections of this chapter make it evident that the aldehydes and ketones closely resemble each other. These two classes of substances are very different, however, in a number of respects. 103. Reducing power. The aldehydes take up oxygen much more readily than the ketones do (HO). They are powerful reducing substances. They slowly oxidize spontaneously in contact with air. Their reducing action is well shown in a number of reactions com- monly employed for the detection of aldehydes. Thus, when an alkaline solution of a compound of copper, such as Fehling's solu- tion,* is heated with an aldehyde, marked precipitation of yellow cuprous hydroxid or red cuprous oxid, or both, results, i. e., the copper compound is reduced, it gives up oxygen to the aldehyde and the latter is converted into an acid. These changes are indi- cated below. A similar reaction takes place with a solution of silver nitrate in ammonium hydroxid. Such a solution is in effect an ammoniacal solution of silver oxid. When it is warmed with an aldehyde a mir- ror of metallic silver is deposited and the aldehyde is converted into acid, thus : * Fehling's solution is an aqueous solution of copper sulfate, potassium hydroxid and sodium potassium tartrate. The latter substance holds excess of cupric hydroxid in solution. When Fehling's solution is heated any cupric oxid formed by the heat is retained in solution. On heating in the presence of reducing substances, however, the blue cupric hydroxid is reduced to the red cuprous oxid, frequently through the stage of the yellow cuprous hydroxid, as follows : The reduction may even proceed to the point of producing a fine precipitate of Cu\ metallic copper, -O - 2Cu. 104 Chemical Notes. 104. Addition products. The power of uniting directly with other substances is a very striking property of the aldehydes. We have already observed that aldehydes as well as ketones unite with hydrogen to form alcohol (102). We have just noted its reducing power, i. e., its power of uniting with oxygen to form acid. We have also noted the fact that aldehydes combine directly with hy- drocyanic acid to form cyanhydrins (102). This power of forming addition products depends, for both aldehydes and ketones, on the double bond of the oxygen atom in the carbonyl radical. The conversion of the oxygen from the carbonyl linkage to the hydroxyl, for example, leaves the carbonyl carbon free to combine with a reacting substance. Thus, the aldehydes form direct combinations as follows : With ammonia* (Hl) : With sodium hydrogen sulfite: f 105. Reaction with alcohols. Acetals. Aldehydes unite with alcohols, in the proportion of one molecule of the former to two of the latter, with elimination of water, as follows : Bodies of this kind are given the generic name of acetal, from the name of the second member of the series. The simplest mem- ber of the group, formed by a union of formaldehyde with methyl alcohol, is known as methylal, * Formaldehyde is an exception. t Most ketones form analogous compounds. Aldehydes and Ketones. 105 106. Isomers. Polymeric modifications. Aldehydes unite with each other under favorable circumstances. Thus, under the influence of dilute potassium hydroxid, two molecules of acetaldehyde unite directly with each other to form a polymeric modification known as aldol, thus : or, Observe the alcohol character of the second carbon group, and the aldehyde character of the last carbon group. Aldol is both an alde- hyde and an alcohol, hence its name - ald(ehyde-alcoh)ol. There is no simple method by which the aldehyde may be regenerated from aldol. The process of union of molecules that cannot be separated by any simple method into the original molecules is known as chemical condensation (108).* Again, three molecules of acetaldehyde unite, under the influ- ence of concentrated acid, to form the polymers, paraldehyde or metaldehyde, each of which has the same empirical formula, C6H12O3. The following constitutional formula is ascribed to paraldehyde. The three acetaldehyde molecules are clearly distinguishable in the formula. Paraldehyde and metaldehyde are probably stereo-isomers. They lack the characteristic properties of the aldehydes, hence do not con- tain the group. Acetaldehyde may be obtained from each by de-polymerization.t * This has no relation to the condensation which a gas undergoes in passing into the liquid state. t There are similar polymers of other aldehydes (108). 106 Chemical Notes. Concentrated caustic alkali converts an aldehyde into a yellowish polymeric (?) compound called aldehyde resin, of unknown consti- tution. Formaldehyde is an exception to the rule. General isomerism. Every primary alcohol will yield a corre- sponding aldehyde. Consequently the number of isomers of the latter, of definite carbon content, equals the number of isomeric primary alcohols of the same carbon content. The aldehydes are isomeric with the corresponding ketones (99). Isomerism of the aldehydes among themselves depends upon the homology of the alkyl groups. 107. General properties. In physical properties the aldehydes show a gradation similar to that of the alcohols. The lower mem- bers of the series are volatile liquids, with a peculiar, pungent odor. They are soluble in water. The higher members are solids, which are insoluble in water and cannot be distilled without decom- position. The aldehydes are neutral substances (117). 108. Formaldehyde, H-CHO, is the simplest member of the paraffin aldehyde series. Properties. Formaldehyde is a gas. It may be condensed to a colorless liquid, which boils at - 21° C. and has a specific gravity of 0.917 at - 80° C. Liquid formaldehyde changes rapidly with rise in temperature, to a polymeric modification known as tri-oxy methylene (CH2O)3. This substance yields formaldehyde on the application of heat. The odor of formaldehyde is very penetrating and sharp. The vapor is very irritating to the eyes and respiratory passages. The taste is intensely irritant. It is a powerful germi- cide. It is soluble in water, alcohol and ether. It readily precipi- tates albuminous and other organic compounds, e. g., one part in 4,000 completely decolorizes wine, precipitating extractive sub- stances with the coloring matter. Preparation. Formaldehyde may be made by oxidizing methyl alcohol. It is frequently present in "wood alcohol." When a red hot platinum spiral is suspended near the surface of warm methyl alcohol, the odor of formaldehyde soon becomes perceptible. Oxygen from the air is occluded by the platinum, the spiral con- tinues to glow, the oxygen is made more active, and the oxidation of the alcohol vapor continues indefinitely. Aldehydes and Ketones. 107 Formalin is the commercial name of an aqueous solution of form- aldehyde containing about 40 per cent, of the substance. Formalin is extensively used industrially as a preservative and as a disinfect- ant. The poisonous qualities of formaldehyde make formalin a dan- gerous preservative of food. " On account of the safety connected with its use, its activity, its permanence of constitution, and its lack of destructive action on vegetable and animal substances,* for- maldehyde is probably the most reliable and the most generally useful of the germicides, when it is not necessary to bring the agent in contact with the human body. It does not affect either the color or structure of clothing or other materials in common use. Its vapor, being of low specific gravity, mixes readily with the air, and penetrates loose fabrics much more deeply than does any other known germicide" [Cushny.] "Formaldehyde lamps" are now on the market. Methyl alcohol is oxidized in them in the presence of platinum gauze. Their use for disinfection purposes is becom- ing general. Paraform. Formaldehyde gas cannot be obtained satisfactorily for disinfecting rooms by merely heating formalin, for the reason that when aqueous solutions of formaldehyde are heated and allowed to evaporate, a white crystalline powder, paraformaldehyde, results. This is an insoluble polymer of formaldehyde (CH2O)m. It is sold under the name of paraform. When heated, formaldehyde is slowly produced from it. Formose. "When a solution of formaldehyde is mixed with lime water or magnesia at the ordinary temperature, it is slowly converted (by an aldol condensation) into a polymeric substance of the formula (CH2O)6, or C6II12O6. The product is a sweet syrup, and its formula and many of its properties indicate a close relation- ship to grape sugar (glucose, C6H]9O6) and fruit sugar (fructose, c„h,A)- it is known as formose. The fact has an interesting bearing on the production of the sugars by plants, which takes place during the assimilation of carbon di-oxid by their chlorophyl (green coloring matter) in presence of sunlight. It has been sug- gested that in the process the carbon di-oxid is reduced to formalde- * This statement applies to formaldehyde vapor in the amounts commonly used for disinfecting purposes. Formalin speedily hardens animal substances like gel- atin, white of egg and meat. 108 Chemical, Notes. hyde, which then undergoes polymerization. The conversion of a solution of the bi-sulfite compound of formaldehyde (104) into starch has, in fact, been observed." * [Cohen.] Formose is a mixture of closely related bodies, one of which is acrose (CH2O)6 or C6H12O6. Another is methylenitan, (CH2O)6-H2O or C6H]0O5. These substances are polymers of formaldehyde. Acrose may be obtained from formaldehyde by heating that substance with lime water. Methylenitan may be obtained by the same treatment of tri-oxymethylene (p. 106). Methose (CH2O)6, or C6H12O6, an- other polymer of formaldehyde, has also been obtained by similar condensation'methods. Acrose and methose are fermentable (82), methylenitan is not. Other sugar-like polymers of formaldehyde have been obtained. The empirical relation between formaldehyde and its sugar con- densation (106) products may be indicated as follows : 6CH2O = C6H12O6 = C6H10O5t + H2O ( Methose, Formaldehyde < Acrose, Methylenitan, t [Glucose] [Starch] The production of formaldehyde in plants and its condensation into sugar and starch, probably occurs by reduction and dehydration, as follows : (1) co2 + h2o = ch2o + o2 Formaldehyde (2) 6CH2O = C6H12O6 Glucose (3) C6H12O6 - H2O = C6H10O5 Starch /H 109. Acetaldehyde, CH3-C^^. Formaldehyde is quite un- like the higher homologues of the aldehyde series in a number of respects. Some of these differences have been alluded to. It is the only aldehyde of the series which does not have an alkyl in *Bokorny has shown that in Spirogyra (sea-weed), formaldehyde sodium bi- sulfite (104) is decomposed by the living cells. The liberated formaldehyde is at once condensed to sugar and precipitated in the cells as starch. This is also equiv- alent to saying that formaldehyde is only a transient product, comparable in a general way to an atom in the nascent condition. t The empirical formulas in this reaction fail to show structural differences. These will be discussed when the carbohydates are considered. Aldehydes and Ketones. 109 union with the carbonyl group. Acetaldehyde is the typical member of the series. Properties. Acetaldehyde is a colorless liquid with a disagree- able odor. Its specific gravity is 0.801 at 0° C. It boils at 21° C., and solidifies at - 121° C. It dissolves readily in water, alcohol and ether. Under favorable conditions it polymerizes into aldol, paraldehyde and metaldehyde. [These products were referred to briefly on page 105.] Paraldehyde is a colorless liquid which boils at 124° C. It has been used in medicine for the production of sleep (somnifacient). Its nauseous taste and disagreeable odor interfere with such use, however. Metaldehyde is a crystalline solid. Preparation. Acetaldehyde may be prepared by oxidizing ethyl alcohol, as in the following reaction.* /H 3CH3CH2OH 4- K2Cr2O7 + 4H2SO4 = 3CH3-C< + Cr2(SOj3 + K2SO4 + 7H„0. \0 The preparation of acetaldehyde by the dry distillation of barium formate and barium acetate has already been indicated (101). Chloral or Tri-chlor aldehyde, CC13-, is an important substi- tution product of acetaldehyde. It is made by treating ethyl alcohol with chlorin. The reaction that ensues is very complicated, several by-products resulting. The essential features of the reaction are (1) the initial transformation of the alcohol into acetaldehyde and (2) the subsequent replacement of two chlorin atoms for two hydrogen atoms in the latter, as follows : CH3-CH2OH 4- Cl2 = CH3-4- 2HC1 CH-+ 3C12 = CC13-+ 3HC1 Chloral is an oily liquid with a very strong penetrating odor. Its specific gravity is 1.541 at 0° C. It boils at 98° C. It poly- merizes, like acetaldehyde, and forms a white amorphous solid- Hot caustic alkali converts it into chloroform, as follows : CC13-+ KOH = CHC13 + KCOOH Potassium formate * Common alcohol usually contains acetaldehyde and acetal. On distilling, these products are present in the "first runnings." 110 Chemical Notes. Potassium cyanid converts chloral, in the presence of water, into di-chlor acetic acid, as follows : cci3-+ KCN + H20 = CHC1-C^H + KOI + HCN Chloral Di-chlor acetic acid Chloral shows even a greater tendency than acetaldehyde to form addition products (104). It unites readily with water, being one of the very few compounds in which a carbon atom is able to hold two hydroxyl radicals (84). On adding to chloral about one-fifth its bulk of water, considerable heat is evolved, chloral hydrate is formed, and the mixture becomes a crystalline solid. The transformation may be indicated as follows: H /H | /OH CC13-C< + H2O = cci-c< \O XOH Chloral Chloral hydrate1 Chloral hydrate, as has just been said, is a crystalline solid. It melts at 46°. It dissolves readily in water and is used in medicine2 as a sleep producer (somnifacient). It is frequently contaminated by chlorin and acetic acid. Chloral hydrate gives a number of the aldehyde reactions, such as reduction of ammoniacal silver oxid solution (103). Chloral hydrate undergoes the changes above indicated for chloral when it is treated with potassium hydroxid or with potassium cyanid. On boiling with concentrated nitric acid, chloral hydrate is oxidized to tri-chlor acetic acid, as follows: CC1SCH<™ + O = CC13C^H + h2o. Chloral hydrate Tri-chlor acetic acid Bromal and lodal are the analogous bromin and iodin com- pounds of acetaldehyde. Ketones. It has already been stated that, although the aldehydes and ke- tones have many qualities in common, they are different in im- 1 Also commonly known as tri-chlor ethidene glycol (84). 2 Chloral itself is not used therapeutically. The chloral of the U. S. Pharma- copoeia is chloral hydrate. Aldehydes and Ketones. 111 portant respects. The lowest member of the series must contain at least three carbon atoms (98). no. Oxidation. The first effect of oxidation of an aldehyde is a change at the end of the chain, as in the production of acetic acid from acetaldehyde: CH-C^ + O = CH3-C(§H The ketones show much less reducing power. They do not re- duce alkaline silver oxid solution (103). They oxidize and split up at the point in the molecule where oxygen is already combined. i ii " Thus, methyl nonyl ketone, CH3 - | CO - | C9H19, for exam- ple, can yield (1) formic acid, CH2O2 and capric acid, C10H20O2, or (2) acetic acid, C2H4O2, and pelargonic acid, C9H18O2, according as the decomposition takes place at the points indicated in the above formula by the vertical lines I and II respectively. The oxidation is actually such that the decomposition takes place at both points simultaneously, so that four acids are obtained. Two of these may be identical. For example, the oxidation of methyl ethyl ketone, CH3-CO-C2H5, produces acetic acid and acetic acid by decomposi- tion at one point of the molecule (II), while if it takes place at the other point (I), formic and propionic acids are produced. In the majority of cases, one of these reactions predominates, usually that one which leaves the carbonyl linked to the smallest alkyl residue. The oxi- dation of the ketones, therefore, affords a means of determining the position which the carbonyl group occupies in the molecule." [Holleman.] in. Addition products. Ketones form direct addition prod- ucts. In general their behavior is the same as the aldehydes (104). The ketones behave differently in this respect toward ammonia. Thus acetone unites with ammonia eliminating water and forming various complex bodies, such as di-acetone amin (104) : 2(CH3)2CO + nh3 = c6h13no + H2o 112. Isomerism. The ketones in marked contrast with the aldehydes, do not show any tendencies in the direction of polymer- ization. Every secondary alcohol yields a corresponding ketone. Therefore the number of isomers of the latter, of definite carbon 112 Chemical Notes. content, equals the number of isomeric secondary alcohols of the same carbon content. Simple ketones are isomeric with the mixed ketones of the same carbon content. Isomerism of the ketones among themselves depends upon the homology of their alkyl rad- icals. 113. General properties. Like the aldehydes, the ketones are neutral substances. The lower members of each homologous series (98) are volatile liquids, with ethereal odors and soluble in water. The higher homologues are solids, insoluble in water and cannot be readily volatilized without decomposition. CTT \ 114. Acetone, ^^/CO, is the most important and the best known ketone. Properties. It is a mobile liquid with agreeable odor, boiling at 57° C. and having a specific gravity of 0.792 at 20° C. It dis- solves many organic compounds and is therefore a useful solvent. Preparation. It may be prepared with greatest ease by the destructive distillation of calcium acetate, as indicated on page 101. Occurrence. Aceton occurs in small quantity in the normal animal organism. It may be present in large quantity in the tissues, urine and breath of diseased people, particularly those suf- fering from diabetes. " Acetonuria " is a frequent pathological condition. Acetone is produced in the dry distillation of various organic substances and is commonly present in crude methyl and ethyl alcohols. Therapeutic derivatives, (a) Chloroform (69), (6) iodoform (70) and (c) sulfonal,* may be prepared from acetone as follows : (a)t CH/C0 + 30,2 = CH >CO + 3HC1 Tri-chlor acetone CC1 \ 2CH / CO + 2Ca(OH)2 = 2CHC13 + 2CaC2H3O2 + H2O + O Calcium acetate (6) Iodoform results under similar conditions when iodin and potassium hydroxid are used. *Sulfonal is an important sleep-producing drug (somnifacient). t In this reaction, carried out at the boiling temperature, the chlorin and the calcium hydroxid are employed in the form of bleaching powder (69). Aldehydes and Ketones. 113 (c) ^>CO + 2C2H -SH = + H2o Ethyl mercaptan Di-methyl di-ethyl mercaptol CH,\ /S - C2H5 _ CHS\ /SO, -C,He CH/ \S - C,H, + 2 CH/ -SO, - C„H, O U O U 4 L 3 Sulfonal * Condensation. When acetone is distilled with concentrated sul- furic acid a liquid, which boils at 163° C., is collected. This sub- stance is a hydrocarbon and a member of the carbocyclic division (16) - mesitylene, or tri-methyl benzene. It results from a trans- formation of three molecules of acetone. The reaction may be indicated graphically, as follows : This is a typical case of chemical condensation (106). The reac- tion also shows an instance of the transformation of a member of one division of organic compounds to another. Relations Between a Typical Paraffin and Its Halogen, Alcohol, Ether, Aldehyde and Ketone Derivatives. i 15. The general relations existing between a typical paraffin and its derivatives in the several types thus far studied are shown in the following formulas : * The production of sulfonal results from an initial union of acetone and ethyl mercaptan in the presence of hydrochloric acid. The oxidation of the initial product is effected by potassium permanganate (45). The chemical names of sul- fonal are acetone di-ethyl sulfon, or di-ethyl sulphon di-methyl methane. CHAPTER VIII. OXYGEN DERIVATIVES OF THE PARAFFINS. IV. FATTY ACIDS. Relations of Fatty Acids to the Paraffins and Other OXY-DERIVATIVES OF THE PARAFFINS. 116. Comparative Results of Oxidation. We have already become familiar with the following general facts : 1. The hydrocarbons yield halogen substitution products (65). 2. The halogen in a mono-halogen derivative may be replaced by hydroxyl, and an alcohol results (78). 3. The alcohols are readily oxidized. When only one atom of oxygen attacks the alcohol molecule, its chemical force results in the removal from the alcohol of two hydrogen atoms. An alde- hyde is formed when the alcohol is a primary one ; a ketone results when the alcohol is a secondary or a tertiary one (97). 4. Whenever the oxidation of an alcohol is carried beyond the initial production of aldehyde or ketone, or whenever the latter bodies are oxidized, acids result (99). 5. When the oxidation of an alcohol, aldehyde, ketone or acid is carried to completion, as in combustion, carbon di-oxid and water re- sult : These general facts may be indicated sequentially as follows: In the oxidation of an alcohol to an aldehyde or to a ketone, two hydrogen atoms are withdrawn and nothing is added. In the oxi- dation of an aldehyde to an acid of the same carbon content, noth- 114 Fatty Acids. 115 ing is withdrawn but one atom of oxygen is added. In the oxida- tion of a ketone, the results are in effect the same, except that, as a rule, two acid molecules of less carbon contents are formed instead of one of like carbon content. The relations of the paraffin oxy-derivatives may be shown em- pirically as follows :* The fatty acids contain one more atom of oxygen than the corre- sponding aldehydes. Compared with the alcohols, each fatty acid' contains an atom of oxygen in place of two atoms of hydrogen. The general formula of the acids is obviously CnH2) O2. In the production of an acid from the above-named substances, the serial radicals are changed as follows : Primary alcohol, -CH2OH -CHO®-^ -COOH Aldehyde, -CHO -COOH Secondary alcohol,! =CHOH $->- =CO ^~COOH Tertiary alcohol, =COH ss->- =CO®->- -COOH Ketone, =COs-> -COOH /OH All the fatty acids contain the mono-valent group - C^q , which is called the carboxyl group (119). Each of the fatty acids may be regarded, therefore, as a carboxyl group united to an alkyl (118). * Ether is not included because it has no relation to the acid. fin the oxidation of a ketone the oxygen unites with a hydrogen atom in one of the alkyl radicals, and the hydroxyl thus formed takes the place of the former alkyl, as is indicated in the following reaction : 116 Chemical Notes. 117. Comparative chemical tendencies. In this connection it is desirable to consider the general tendencies of the oxy-derivatives under review. The following summary indicates these tendencies. Chemically inert Paraffin R-H Basic Alcohol * R-OH Chemically active Neutral f Aldehyde Ketone R-CHO r/CO Acid Fatty acid R-COOH Thus, the introduction of oxygen changes an inert paraffin into chemically active substances. The introduction of one atom of oxygen produces an alcohol-a weak base. The alcohols unite with acids to form salts : c2h5oh + HC1 = c2h5ci + h2o Continued oxidation (elimination of an equivalent of hydrogen, jj/(O), produces aldehydes or ketones - neutral substances having no special affinities for acids or bases [except ammonia (111)], al- though they are chemically active in many other respects, especially in their avidity for oxygen. Further oxidation produces acids of different degrees of strength. All of these acids are relatively weak, however - much weaker than the common mineral acids (39). Homologous Series. 118. A list of the fatty acids is given on the opposite page. Nomenclature. 119. Acids. Many of the members of the homologous series of acids listed on page 117 are constituents of the animal and vegetable fats, oils and waxes. The higher members were first obtained from fats. For this reason they have received the generic name, fatty acid. The fatty acids might be called carboxyl compounds (116), such as hydrogen carboxyl, H - COOH, methyl carboxyl, CH3 - COOH, etc. The fatty acids higher in the series than acetic acid may also be, and are, regarded as mono-, di- or poly-alkyl acetic acids (p. 117) The names derived in this way express clearly the constitution of * The alcohols are neutral to litmus and similar indicators. f The aldehydes and ketones are neutral in the sense that they have in general no special affinities for acids or bases. Fatty Acids. 117 the acids, and are similar to the carbinols in chemical definiteness (76). The names in general use, however, have been derived from the original sources of the acids. The names of some of the higher members of the fatty acid series are derived, like those of their Fatty Acids.* CnH2nO2. Name. c Formula. Melting Point. Boiling Point at 760 mm. Specific Gravity 0° C. Formic acid H-COOH 8° C. 101°C. 1.2311 Acetic acid CH-COOH 17 118 1.0522 Propionic acid C2H5-COOH -24 141 1.013 Butyric acid C3H7-COOH - 8 162 0.978 Iso-butyric acid (CH3)2=CH-COOH 154 0.965 Valeric acid C4H9COOH -59 185 0.956 Iso-valeric acid (CH3) 2-CH-CH2-COOH 174 0.947 CH3X Methyl ethyl acetic acid >CH-COOH - 177 0.941 C2H5 Tri-methyl acetic acid (CH2)3=C-COOH 35 164 0.9053 Caproic (iso-butyl acetic) acid. (CH3)2=CH-(CH2)2-COOH - 2 205 0.945 CEnanthylic acid C6H13-COOH -11 223 0.931 Caprylic acid C7Hj-COOH 16 239 0.927 Pelargonic acid C8H„-COOH 13 1864 0.911s Capric acid CgHjg-COOH 31 268 0.930s Undecylic acid C10H21-COOH 28 280 Lauric acid CnH23-COOH 44 225 0.875'] Tri-decylic acid C19H9-COOH 41 236 Myristic acid C13H27-COOH 54 250 0.862 Iso-cetic acid Ci"h«-COOH 55 257 O Palmitic acid C^Ho,-COOH 63 271 r 0.852 Margaric acid C1RH„-COOH 60 277 Stearic acid C H„-COOH 69 291 0.845. Arachidic acid CinHTO-COOH 75 Medullic acid C20H41-COOH 72 - - Behenic acid C21H43-COOH 77 Lignoceric acid c23h^-cooh 80 Carnaubic acid C9»H47-COOH 72 Hvenic acid C24H49-COOH 77 Cerotic acid cX-cooh 78 . Melissic acid C29H59-COOH 90 - - 1AtlO°C. 2 At 16.5° C. 3 At 50° C. 4Atl00mm. 5 At 12° C. 6 At 27° C. 7 At 100 mm. 8 At the melting point. parent hydrocarbons (51), from the greek names of the numerals corresponding to the number of carbon atoms in the acid molecule. 120. Acyls. The hydroxyl radical of the carboxyl group is mono-valent, like the carboxyl group itself: * A number of isomers have been omitted. 118 Chemical Notes. That portion of the acid which may be regarded as being attached to the hydroxyl group is obviously also monovalent: This residue of the acid has the properties of a radical; it enters into chemical union with various atoms and radicals to form special compounds (130). This residue is given the generic name, acid radical or better still, acyl. An acyl bears the same relation to a fatty acid that an alkyl bears to a paraffin. Like the alkyls, also, the acyls never exist as free substances, but are always attached to other atoms or groups as parts of more complex compounds. The name of the acyl is the same as that of the acid, with the ic suffix of the name of the acid changed to yl in the suffix of the name of the acyl. [Compare with the alkyl nomenclature (58).] 12i. Summary The following table gives the names of the first six acids of the fatty acid series and of their acyls, and indi- cates the derivation of the names employed : Acid. Acyl. Derivation of Names. Name. Formula. Name. Formula. Formic acid Acetic acid Propionic acid... Butyric acid Valeric acid Caproic acid H -COOH CH3 -COOH C2H5 -COOH C3H7 -COOH C4H9 -COOH C5Hu-COOH Formyl Acetyl Propionyl... Butyryl Valeryl Caproyl H - CO- CH3 - CO- C2H5 -CO- c3h7 - co- c4h9 - co- C5HU-CO- formica, an ant. acetum, vinegar. irpuroQ, first; iVim, fat (137). butyrum, butter. Valeriana officina- lis, valerian. capra, a goat. There are many methods by which fatty acids may be made. The most important of these are the following : 122. (A) Oxidation of primary alcohols and aldehydes (81). Methods of Preparation. 123. (B) Hydration of alkyl cyanids. (a) An alkyl cyanid may be produced as follows (72): CH3-I + K-C = N = CH.-C=N +KI Methyl cyanid Fatty Acids. 119 (6) An alkyl cyanid may be hydrated through the action of dilute acid or alkali, as follows : CH-C = N +2H2O+HC1 = CH,-C^H+NH4C1 O Z O xNf 1 4 In this change oxygen and hydroxyl are added to the cyanid. The bonds are broken between the nitrogen and the carbon in the nitril * group, -C=N. The nitrogen unites with hydrogen to form ammonia. 124. (C) Methods of preparing alcohols and acids of high car- bon contents from alcohols and acids of lower carbon contents, and vice versa. " The above reactions (123) offer a simple method for passing from one member of a series to the next. (a) "Methyl alcohol may be converted into the iodid, the cyanid, and finally, by hydrolysis, into acetic acid. On distilling calcium acetate with calcium formate, acetaldehyde is produced (101), which yields ethyl alcohol on reduction : HI KCN H„0 /OH CH3-OH^CH,-Is-^CH.-CN^CH,-C<^ O O O 6 nO (H-COO)„Ca ) ZH h2 r ^CH,-C< ^CH,-CH2-OH (CH -COO) Ca J \O 32 (6) "The reverse process may be effected by distilling the alkali salt of the acid with soda-lime. Potassium acetate forms marsh gas, which may be converted into methyl chlorid, methyl alcohol and formic acid " (Cohen) : /ONa NaOH Cl2 KOH O2 /OH CH„-C\ ->CII .^CKCl^CH.-OH^H-tY 3 \Q 4 3 3 \Q 125. (D) Action of carbon mon-oxid upon the sodium alcohol- ates heated to 1600 - 200°C., thus : CH3-ONa+CO = CH3-C^Na Sodium acetate f * The alkyl cyanids are also called fatty acid nitrils. t The free acid may be obtained by treating its salt with a strong acid (136) : /ONa ,OH CH-C/ +HC1 = CH3-C< 4-NaCl 120 Chemical Notes. Constitution. 126. Deductions from differences in boiling points. The nor- mal boiling points of related ethane derivatives are indicated in the following summary : The substitution of a hydroxyl radical for a hydrogen atom in ethane raises the boiling point of the compound considerably. The transformation of the hydroxyl radical of the alcohol to a carbonyl radical in the aldehyde, and the associated loss of hydrogen, result in a considerable lowering of the boiling point of the aldehyde. The conversion of the latter into an acid again raises the boiling point, presumably because of the introduction of a hydroxyl radical without loss of hydrogen. These statements apply equally well to the other members of the fatty acid series. The simplest acids of the fatty acid series are formic acid and acetic acid (135, 136). In the following observations they are used merely as illustrations of the facts common to all their associates in the fatty acid series. 127. Constitution of the simplest fatty acids. Formic acid, /OH H - , may be made from iodoform or chloroform as follows : In this reaction it is obvious that each chlorin atom is replaced by a hydroxyl radical. The tri-hydroxy compound that may be presumed to occur, but which is too unstable to be detected, imme- diately loses a hydrogen atom and a hydroxyl radical to form water, and the anhydrid, formic acid, containing the carboxyl group, Fatty Acids. 121 results. The above reaction is analogous to the formation of phos- phoric acid from phosphorus penta-chlorid : Chloral and sodium hydroxid undergo the following changes : This reaction also signifies the presence in formic acid of a carboxyl group. The latter deduction is also necessitated by the result of oxidation of formaldehyde : Acetic acid may be made, by oxidation, directly from ethyl alco- hol. The following consecutive productions show that in the mole- cule of ethyl alcohol two carbon atoms are directly united : CHSI s > <|HS > CH2OH ch3i ' ch3 " ch3 ch3 The oxidation of ethyl alcohol to acid cannot break the bond between the two carbon atoms. This bond exists in acetic acid, as is shown in the following synthetic reactions (123) : The relation between formaldehyde and formic acid was indicated 122 Chemical Notes. on page 121. The same relation exists between acetaldehyde and acetic acid : That acetic acid is composed of the carboxyl group united to an alkyl is shown even more definitely in the following reactions on acetic acid : This reaction proves the presence of hydroxyl in the acetic acid molecule (99). The second atom of oxygen in the acid cannot be replaced by chlorin in this way, and consequently is in the carbonyl condition (99). It is obvious therefore, that these homologous acids contain the carboxyl group. In formic acid the group is united to hydrogen, in acetic acid it is united to methyl, in the higher homologues it is united in the same way to alkyl radicals (R): Isomerism. 128. Every primary alcohol will yield a mono-carboxylic acid. Consequently there are as many isomeric acids of that type as there are isomeric primary alcohols of the same carbon content. The isomerism of the fatty acids depends, therefore, on the isomerism of the radicals attached to the carboxyl group. Physical Properties. 129. The lower homologues of the series are liquids at ordinary temperatures. The higher members, beginning with capric acid, C9H19COOH, are solids at room temperature. The liquid homo- logues can be distilled without decomposition ; the solid homologues cannot be distilled at ordinary pressures without decomposition. Boiling points increase about 19° for each addition of CH2 to the molecule. As the carbon content increases, specific gravity decreases, and true hydrocarbon characters are approached. Fatty Acids. 123 The lower fatty acids dissolve readily in water. Solubility in water decreases as carbon content increases. All of the fatty acids dissolve in alcohol; they are particularly soluble in ether. Solutions of the fatty acids show acid properties when tested with litmus and various similar indicators. Relative acidity dimin- ishes of course, with increase in molecular weight. Chemical Transformations. The chemical properties of the fatty acids are indicated in a general way by the subjoined summary of a few of the many im- portant derivatives, acetic acid being used in most of the formulas to illustrate the general facts cited. 130. Changes in the carboxyl group. Important derivatives resulting from changes in the carboxyl group are the following : (1) Salts, resulting from the substitution of the hydrogen of the carboxyl group by an atom of a metallic element. (2) Esters, resulting from the substitution of the hydrogen of the carboxyl group by an alkyl. (3) Halogen derivatives, resulting from the substitution of the hydroxyl radical by a halogen atom. The following reactions give examples of the above named derivatives. 1. Salt: CH3-C^H + NaOH = CH3-C^Na + H2O Acetic acid Sodium acetate 2. Ester: CHs-c(°H + CH-OH = CH -c(°"CH3 + H2O Methyl alcohol Methyl acetate The resemblance between alcohols and hydroxids is here again clearly indicated (79). 3. Halogen derivative (acid chlorid) : CH3-<H 4- PC15 = CH3-C^ + POC13 4- HC1 Acetyl chlorid 131. Changes in the alkyl radicals occur under certain con- ditions, and important derivatives of the acids are thus produced. 124 Chemical Notes. Chlorin, in gaseous form, attacks the alkyl radical without affecting the carboxyl group. Chlor acetic acids, for example, re- sult from the following reactions : CH -C^°H + Cl2 = CH2C1-+ HC1 Mono-chlor acetic acid CH2C1-C^H + Cl2 = CHC1 - C^qH + HC1 Di-chlor acetic acid CHC1 -C^°H + Cl2 = CC1 -+ HC1 Tri-chlor acetic acid This action is analogous to the action of gaseous halogens on the paraffins (65). Like the halogen derivatives of the paraffins, also, such halogen derivatives of the acids readily exchange chlorin for equivalent atoms or radicals, as in the following typical reactions : (a) CH2C1-+ H2O = CH2(OH)-+ HC1 Oxy-acetic acid (6) CH2C1~c(°H + 2NH3 = CH2(NH2)-C(°H + NH,C1 Amino-acetic acid (c) CH2C1-C^H + KCN = CH2(CN)-C^H + KC1 Cyano-acetic acid The position in the fatty acids of the halogen atom or atoms, or of any equivalent such as hydroxyl, is usually denoted by greek letters applied to each carbon group in the alkyl radical, beginning with the carbon atom to which the hydroxyl is attached. Thus, there are three oxy-derivatives of normal butyric acid, as follows : CH3-CH2-CH2-COOH, n-butyric acid y a (a) CH-CH-CH(OH)-COOH, a-oxy-butyric acid (6) CH - CH(OH)-CH2-COOH, /3-oxy-butyric acid (c) CH2(OH)-CH2-CH2-COOH, 7-oxy-butyric acid 132. Electrolysis. The electric current converts the fatty Fatty Acids. 125 acids into the corresponding paraffins, and into carbon dioxid and hydrogen, as follows (44): + pole - pole CH,-COOH CH3 CO2 H 3 • = I + + I CH3-COCH CH3 CO2 H 133. Decomposition by heat. We have already considered the preparation of paraffins (55), aldehydes and ketones (101) from salts of fatty acids in the following reactions: (a) CH,-COONa + NaOH = CH, + Na2CO„ \ / o * o Z7X CJL-COCK H-COCK fWTrT ^/H OT> (ty CH - COCK H-COC)/Ba *CH3 C^q 4- -jBaCO3 z CH3-COO\ CHa ~ _ (c) CH3-COO/Ba ~ CH/CO + BaCO Sources of the Fatty Acids. 134. Fatty acids combined with glycerol (glycerin) constitute the main bulk of fats and oils. Free fatty acids occur in the latter in variable quantities. Fatty acids are present in the intestinal contents of all mammals and of many of the lower animals, also in various plants. The lower fatty acids are formed in the "acid fer- mentation " of alcohol and of starchy and sugary mixtures, and also, in the dry distillation of wood (83). Free acetic acid is prominent in vinegar. Butyric acid in the free state is conspicuous in rancid butter. Practically all of the animal and vegetable tissues and organs contain more or less fatty acid in combined forms. Typical Fatty Acids. /OH 135. Formic acid, H - > is the first member of the fatty acid series. Physical properties. Formic acid is a colorless, mobile liquid at ordinary temperatures. It is crystalline at 0° C., melts at 8° C., and boils at 101° C. Its specific gravity at 20° C. is 1.220. It has a very pungent odor and exerts strong corrosive action. Ap- plied to the skin, for example, it causes pain and quickly raises blisters. It is readily soluble in water, alcohol and ether. Its salts, which are called formates, are also relatively soluble com- pounds. 126 Chemical Notes. Occurrence. Formic acid occurs in the free state in the bodies of ants. Its name is due to this fact (121). It also occurs in small quantities in other animals, is present in minute amounts in perspi- ration and other animal fluids, and occurs in various plants ; in the shoots of the pine, for example. It may be separated from all these sources by distillation. It is found among the products of fermenta- tion of various starchy matters and sugars. Formic acid occurs among the products formed by the oxidation of various organic substances, and in such cases represents the last stage before con- version into carbon dioxid and water (116). Preparation. Formic acid may be prepared artificially by many methods, among which the following throw the most light on its chemical nature : (1) By the oxidation of methyl alcohol and formaldehyde : TT ATT /ATT 0 TT 0 TT H-CH2OHs^H-C< o C< o (2) By heating hydrocyanic acid with acids or alkalies (123): HCN + 2H2O + HC1 = H-C^ + NH4C1 (3) By boiling chloroform with caustic alkali (127): CHC13 + 3KOH = H-C^qH + H2O + 3KC1 (4) By treatment of chloral with caustic alkali (109) : CC13 - + NaOH = H-C^q + CHC13 (5) By the action of carbon mon-oxid on hot potassium hydroxid : CO + KOH = H-C^°K (6) By the action of metallic potassium on moist carbon di-oxid (carbonic acid) : 2CO. + H2O + 2K = H-C^qK + HKCO, (7) By the action of sodium-amalgam upon aqueous solution of ammonium carbonate : (NH^CO, + H2 = + H2O + NHS Fatty Acids. 127 The last two methods suggest that formic acid is reduced carbonic acid. H_§>0=° - O = H-C(gH Carbonic acid Formic acid " It is extremely important to bear this fact in mind, as it is of great assistance in enabling us to understand the relations existing between the two acids, and between them and all other acids of carbon. All the acids of carbon may be regarded as derivatives of either formic acid or carbonic acid." [Remsen.] Chemical properties. Formic acid differs from all the other fatty acids (a) in readily undergoing oxidation, i. e., in showing marked reducing action, (6) in being easily decomposed into carbon mon- oxid and water, (c) and in showing the properties not only of a mono-basic acid but also those of an aldehyde. a. When a solution of silver nitrate is treated with sodium form- ate, silver formate results. The latter compound is transformed by reduction as follows: 2H-C^§Ag = 2Ag + CO2+ H-q(™ Silver formate b. Heated with concentrated sulfuric acid, formic acid is decom- posed as follows : h-<oH - H*° + co c. That formic acid possesses aldehyde characters may be seen on comparing the following formulas : H-<0 ' h-°^H Formaldehyd Formic acid (as previously written) (transposed) The above transposed formula (II) of formic acid suggests that the latter substance is hydroxy aldehyde. It might be called oxy- formaldehyde. Like all aldehydes formic acid attracts oxygen, i. e., it reduces, and in turn is converted into carbon dioxid and water: /OTT H-c^o +O = CO2 + H2O 128 Chemical Notes. /OH 136. Acetic acid, CH3-, is the second acid of the fatty- acid series. This acid was the first to be discovered. The name acid is derived from acetum, the latin for vinegar. Acetic acid is the characteristic constituent of vinegar. Physical Properties. Pure acetic acid is a colorless, mobile liquid at ordinary room temperature. When cooled to about 16° C. or below, pure concentrated (anhydrous) acetic acid solidifies to a white crystalline mass, which resembles crushed ice. The anhydrous acid is called glacial acetic acid for this reason. Ordinary dilute solu- tions of acetic acid do not show the same glacial transformation at 16° C. Acetic acid has a very penetrating acid odor and the familiar taste of vinegar. The concentrated acid has an effect on the skin similar to that exerted by formic acid, raising blisters and causing pain. It boils at 118° C. and at 20° C. has a specific gravity of 1.050. It dissolves in water in all proportions and is an excellent solvent of many organic compounds. It dissolves readily, also, in alcohol and ether. Occurrence. Acetic acid is present in minute proportions in the juices of certain plants and in a few animal secretions. It is com- bined with glycerol in some vegetable fatty matters. It is the characteristic constituent of vinegar and is one of the products of several types of acid fermentation of alcoholic and sugar-contain- ing liquids. It is also produced in the decay of organic matter. Vinegars are produced by the oxidation of liquids containing ethyl alcohol. In " acetic fermentation " this oxidation is usually effected by the "acetic ferment," a microscopic organism (Myco- derma aceti) commonly called " mother-of-vinegar." Acetic fer- mentation is frequently preceded by alcoholic fermentation (82). Thus, considerable acetic acid is made for commercial purposes by subjecting poor wine to the acetic fermentation process, i. e., by ex- posing it to the air for access of the fermentation organisms, which, like many similar organisms, are always present in the atmosphere. Vinegars are distinguished according to their origin, as beer vinegar, cider vinegar, fruit vinegar, wine vinegar, etc. Ordinary vinegars contain from about 5 to 15 per cent, of acetic acid. Liquids containing 15 per cent, or more of alcohol do not turn Fatty Acids. 129 sour spontaneously. The vinegar ferment is killed by that propor- tion of alcohol. A so-called " quick vinegar process " consists in enlarging the contact surface of the alcoholic liquid with the air and thereby in- creasing the rate of oxidation. This is accomplished by allowing the alcoholic liquid to drop on beechwood shavings, moistened with strong vinegar in the first place and contained in a vat with a perforated bottom and with openings at the sides. The openings allow the egress of descending liquid and the ingress of ascending air. The shavings distribute the liquid over a relatively large surface and also serve as a " feeding-ground " for the " mother-of- vinegar," both of which conditions favor the rapid formation of acetic acid. If the access of air is impeded, acetaldehyde is formed. When oxidation becomes too vigorous, carbon di-oxid and water result. Wood vinegar is obtained by the dry distillation of wood (83). Acetic acid, methyl alcohol, acetone and various other products are contained in it. The mixture is also called pyroligneous acid. Preparation. Acetic acid may be prepared by various methods (122). It is produced on a large scale by the oxidation of alcohol, as in the acetic fermentation process just described, and also by the dry distillation of wood and other organic products, such as sugar. The separation of the acid from such mixtures may be effected without particular difficulty. Thus, in the case of the wood vinegar, the liquid is neutralized with lime. Calcium acetate is formed. The methyl alcohol and the acetone are then removed by distillation. After concentrating the solution of the calcium acetate, resinous matters are mechanically removed from the sur- face, the solution is evaporated to dryness, and the dry residue is gently heated to burn out most of the carbonaceous impurities. This ignited mass is known as " gray acetate." Acetic acid may be obtained from the latter by distilling the acetate with concentrated hydrochloric acid, which decomposes the calcium salt as follows : CfT COO ™3 /Ca + 2HC1 = 2CH„-COOH + CaCl2 ch3-coo/ 3 2 Chemical properties. Acetic acid is unlike formic acid, but is like all the other fatty acids, in resisting oxidation and therefore in Chemical Notes. 130 being devoid of reducing action. It does not manifest aldehyde properties. Like all of the fatty acids, it is monobasic and, like all of its homologues except formic acid, forms two classes of de- rivatives : (a) Those which result from changes in the carboxyl group ; (6) Those which result from changes in the alkyl radical (131). An acetate results from the replacement of the hydrogen of the carboxyl group by an atom of a positive element, thus : CH3-C^H + NaOH = CH3-C^QNa + H2O Sodium Acetate 2CH3-C^H + PbO=^_^§§>Pb + H2O Lead Acetate Nearly all of the acetates are crystalline substances, which readily dissolve in water. On decomposition acetates yield methane (55), ethane (132), aldehyde (101), acetone (101), or other products, ac- cording to the method employed. /OTT 137. Propionic acid, C2H5 -, accompanies acetic acid in wood vinegar, and is also formed in acid fermentation processes. It is soluble in water but may be separated from its aqueous solu- tion by calcium chlorid. The acid floats like an oil on the calcium chlorid solution. This resemblance to oil gave it the name it bears (7rpwTO9, first; ttIwv, fat). Propionic acid is the first of the fatty acids which resembles the higher fatty acids. Formic acid is very different from its homo- logues (135) and acetic acid represents a transition between formic acid and the higher homologues. There are no isomeric forms of the first three fatty acids. /OH 138. Butyric acid, C3Hr - , exists in two isomeric forms, normal and iso. Both of these occur in nature. The normal acid is combined with glycerol in butter, hence its name (121). The odor of rancid butter is due to this acid. Normal butyric acid occurs in perspiration and in other animal secretions, and is formed in the decay and oxidation of albuminous matter. It is also produced in "butyric fermentation" through the combined Fatty Acids. 131 action of microorganisms known as the "lactic acid" and "butyric acid" ferments. The transformation may be represented as follows, starting with grape sugar (glucose): CfiH12O6=2C„HfiO, o o .5 o o Glucose Lactic acid 2CsH6O3 = C3H,-C(2H + 2CO3+ 2Hs Acetic acid and caproic acid are also formed from the sugar in this process. These acids are also formed by analogous cleavages of other substances. Iso-butyric acid is found in various plants. /OH 139. Valeric acid, C4H9- C^q • Four isomers of valeric acid are possible; four are known. Normal or ordinary valeric acid occurs in the free state, and com- bined with glycerol in fats, in both the animal and vegetable king- doms. It is a conspicuous constituent of valerian root ( Valeriana officinalis}, whence its name (121). It is an acid with unpleasant odor and is less soluble in water than the lower fatty acids. /OH 140. Caproic acid, C5H10 - CKq ' occurs combined with glycerol in various animal and vegetable fats, especially in goat butter (121). It accompanies butyric acid in butyric fermentation. /OH 141. Palmitic acid, C15H31-C^q , occurs free in palm oil. Combined with glycerol it forms one of the main constituents of animal and some vegetable fats. It crystallizes in needles from alcohol. The crystalline solid melts at 60° C. /OH 142. Stearic acid, C17H35-C^q , combined with glycerol, is associated with palmitic acid as one of the leading constituents of animal fats. Like palmitic acid, it crystallizes from alcohol in needles. The latter melt at 68° C. Waxes. I43« Waxes are compounds of higher fatty acids and glycerol, in the proportion of one molecule of each. Ordinary bee's wax is a 132 Chemical Notes. /OTT mixture of cerotic acid, C26H53- C^q and myricyl palmitic ester. The latter substance may be formed in the following reaction : c15hs1-c(qH + CMH6-OH = C15H31-CO-O-CmH61 + h2o Palmitic acid Myricyl alcohol Myricyl palmitic ester Fats and Fatty Oils. 144. The fats and fatty oils will be given special attention in our study of glycerol. For the present it is sufficient for us to know that a fat or an oil consists of one molecule of glycerol com- bined with three molecules of fatty acid, as is indicated in the fol- lowing formula of palmitin, a typical fat: The fats are complicated esters (130). Soaps. 145. Soaps are the alkali salts of the higher fatty acids. The soaps are formed directly from the fatty acids, or by boiling fats with caustic alkalies. The latter process results in hydration of the fat, and is known as the process of saponification. The reaction in the saponification of a fat may be illustrated as follows : The sodium salts of the higher fatty acids constitute the hard soaps. The potassium salts of these acids are the soft soaps. Fatty Acids. 133 Relations Between a Typical Paraffin and its Halogen and Oxygen Derivatives. 146. We have thus far considered the qualities of the most important paraffins and their halogen substitution products; also the leading representatives of five classes of oxygen derivatives. We have found that the paraffins are carbon-hydrogen com- pounds to which nothing can be added directly, but into which halogens or other atoms or various radicals can be introduced. The number of halogen derivatives of each paraffin was found to depend on the number of hydrogen atoms contained in it. The alcohols are the hydroxids of paraffin radicals or alkyls. The ethers are the oxids of the same radicals. An aldehyde is a compound of an alkyl, a hydrogen atom and a carbonyl radical. A ketone is an aldehyde in which a hydrogen atom has been replaced by an alkyl. An acid is a compound of alkyl, carbonyl and hydroxyl, or is carbonic acid in which a hydroxyl radical has been replaced by an alkyl. These relations are expressed below, where R indicates any alkyl: Paraffin, R-H C2H6, ethane. Paraffin haloid, R-Cl C2H5-Cl, * ethyl mono-chlorid. Alcohol, R-OH C2H5-OH, ethyl alcohol. Aldehyde, R-CH3-CHO, acetaldehyde. R CH Ketone, j^>C=O CH3/CO' acetone. Acid, R_C^H CH3-COOH, acetic acid.