None
y -I sopropyl Itaconic Acid, m.p. 189°. y-Isobutyl Itaconic Acid, m.p. 160°. y-n.- Hexyl Itaconic Acid, m.p. 129°. Teraconic Acid, y-Dimethyl Itaconic Acid. (CH3)2C=C.CO2H, | m.p. 162°, is prepared from terebic acid (p. 517, and CH2CO2H Vol. II.) ; and by the condensation of succinic ester and acetone by means of huric and Itaconic acid. m.p. 181° with decomposition. CHj=C.COaH a-Methyl Itaconic Acid, m,p. 150°, is obtained from pyro- CHa— CH.C02H cinchonic acid (below) ; anhydride, m.p. 63°, is produced by heating anhydro- methyl aconitic acid (C. 1906, II. 21). CH2=C— COOH, aa-Dimethyl Itaconic Acid, \ m.p. 141°, is prepared from (CH3)2CCOOH a-bromotrimethyl succinic acid and diethyl aniline ; anhydride, b.p. 210-215° ; diethyl ester, b.p. 20 127° (C. 1902, I. 180 ; 1904, 1. 434). ay-Dimethyl Itaconic Acid, CH3CH : C(COOH).CH(CH3)COOH. m.p. 202° (anhydride, b.p.M 131°) and a-Ethyl Itaconic Acid, CH2 : C(COOH).CH(C2H5)COOH (anhydride, m.p. 52), result from boiling methyl ethyl maleic acid (p. 519) with sodium hydroxide solution ; the former also, from ay-dimethyl paraconic acid by boiling it with NaOC2H6 solution (B. 39, 1535). The alkyl itaconic acids mostly have no sharp melting points, owing to their tendency to form anhydrides. Homologous Citraconic Acids, Alkyl Maleic Acids. CH3— CH,— C— C02H y-Methyl Citraconic A cid, Ethyl Maleic A cid, \\ , m.p. 1 00°, CH.CO2H can also be obtained by heating /?-ethyl malic acid (B. 37, 2382 ; 38, 2737) ; anhydride, b.p. 229°, is obtained from ethyl fumaric acid, p. 519) by heating it with acetyl chloride. When vapourised with ammonium it forms the imide, m.p. 141°. y-Ethyl Citraconic Acid, n-Propyl Maleic Acid, m.p. 94°; anhydride, b.p. 224°. y-Propyl Citraconic Acid, m.p. 80°. y-Isopropyl Citraconic Acid, m.p. 78°. y-Isobutyl Citraconic Acid, m.p. 75°. y-Hexyl Citraconic Acid, m.p. 86°. (CH8)2CH.C— C(X y-Dimethyl Citraconic Anhydride, I! >O, m.p. 5°, b.p.gl 138° CH.CO/ (C. 1899, I. 668, 780). The y-alkyl citraconic acids or monoalkyl maleic acids do not melt sharply on account of the formation of anhydrides. The a -alkyl citraconic or dialkyl maleic acids only exist as anhydrides, which are formed when the acid is liberated from its salts by stronger acids. Pyrocinchonic Anhydride, Dimethyl Maleic Anhydride, a-Methyl Citraconic CH3.CCOX Anhydride, >O, m.p. 96°, b.p. 223°, is formed when cinchonic acid CH3.CCO/ (q.v.) is heated : CO2H CO.O.CO -H20 | CHa.CH.CH.CO,H ^->CH3C=C CO— O— CHa CH, Cinchonic Acid. Pyrocinchonic Anhydride. It also results, together with terebic acid, when turpentine oil is oxidized with nitric acid ; from a-dichloro- and a-dibromo-propionic acid and silver (B. 18, 826, 835) ; by condensation of pyroracemic acid and sodium suocinate by means of ATICONIC ACIDS 51$ acetic anhydride (A. 304, 158) ; by distillation of ajS-dimethyl malic acid (p. 556) under reduced pressure (a method of preparation) ; by distillation of anhydro- methyl aconitic acid (C. 1906, II. 21). Dimethyl ester, b.p. 219°, and diethyl ester, b.p. 237°, are prepared from silver pyrocinchonate and iodo-alkyls (B. 33, 1410). The solution of pyrocinchonic anhydride reacts strongly acid and decomposes alkali salts forming pyrocincho- nates, the constitution of which has already (p. 513) been discussed. Ferric chloride produces a dark red coloration in pyrocinchonic anhydride solutions. Reduction produces two dimethyl succinic acids (p. 494). It unites with chlorine to form dimethyl dichlorosuccinic anhydride (B. 26, R. 190). When boiled with 20 per cent, sodium hydroxide solution, pyrocinchonic acid is converted into dimethyl fumaric acid and /J-methyl itaconic acid (A. 304, 156). Pyrocinchonic ester, when heated with alcoholic ammonia, yields amino-dimethyl-succinimide (p. 557) and pyrocinchonimide, m.p. 119° (B. 33, 1408), which, on hydrolysis yields, in part, /J-methyl itaconic acid. Methyl Ethyl Maleic Anhydride, b.p. 236°, is formed by condensation of pyro- tartaric acid and pyroracemic acid, by means of acetic anhydride (A. 267, 214) ; by distillation of ay-dimethyl paraconic acid whereby a-methyl j8y-pentinic acid is also formed (B. 39, 1535) ; by the slow distillation of methyl ethyl malic acid ; imide, m.p. 67° ; dimethyl ester, b.p. 235°. The imide and anhydride can also be obtained from the destruction of haematin or haematinic acid (comp. haemoglobin) (A. 345, i). Methyl Propyl Maleic Anhydride, b.p. 242° (imide, m.p. 57°) and Methyl Isopropyl Maleic Anhydride, b.p. 241° (imide, m.p. 45°) are obtained from methyl propyl and methyl isopropyl malic acid (A. 346, i). Xeronic Anhydride, Diethyl Maleic Anhydride, b.p. 242°, is prepared by heating citraconic anhydride (A. 346, i). Homologous Mesaconic Acids, A Iky I Fumaric Acids. For the formation of alkyl mesaconic acids from the corresponding alkyl itaconic and alkyl citraconic acids, seep. 517. The products of reaction of alcoholic potassium hydroxide and the y-dibromo- derivatives of monoalkyl acetoacetic ester belong to the alkyl fumaric acid series (C. 1899, I. 780) ; hydroxytetrinic acid being mesaconic acid, and hydroxy- pentinic acid being ethyl fumaric acid, etc. (p. 420). The reaction is most simply explained by the assumption that keto- or hydroxy- aldehydic acids are first formed, which are then converted into unsaturated car- boxylic acids (B. 32, 1005) : X8CH.COCHR'.CO2R - > OCH.CO.CHR'.CO2R O.CH.C(OH)=CR'.CO2R - > CO2H.CH : CR'.CO2R. Also, monoalkyl fumaric acids are obtained from monoalkyl ethane tri- carboxylic acids by the introduction of halogen and subsequent splitting off of halogen acid and CO2 (B. 24, 2008). Ethyl Fumaric Acid, y-Methyl Mesaconic Acid, m.p. 194°- n.-Propyl Fumaric Acid, y-Ethy I Mesaconic Acid, m.p. 174°. Isopropyl Fumaric Acid, y-Dimethyl Mesaconic Acid, m.p. 184°. n.-Butyl Fumaric Acid, y-Propyl Mesaconic Acid, m.p. 170°. y-Isopropyl Mesaconic Acid, m.p. 185°. y-Isobutyl Mesaconic Acid, m.p. 205°. y-Hexyl Mesaconic Acid, m.p. 153°. Dimethyl Fumaric Acid, a-Methyl Mesaconic Acid, m.p. 239° ; diethyl ester, b.p. 235°, is formed when diazopropionic ester is heated (p. 410) (B. 37, 1272). Aticonic Acids. — For the formation of these acids from the alkyl itaconic acids by synthetic methods, see p. 517. Dimethyl Aticonic Acid, i-Methyl Vinyl PT-T PTT PO H" Succinic Acid, y-Methyl Methylene Pyrotartaric Acid, CH3^C'^H<^CC)2H * m.p. 146°, results when teraconic acid is boiled with sodium hydroxide solu- CH tion. Isobutyl Aticonic Acid, 2-Isopropyl Vinyl Succinic Acid, CH8>CH.CH=: CH.CH<£Q 2^°2H, m.p. 93°. Hexyl Aticonic Acid, 2- Amy I Vinyl Succinic Acid, 520 ORGANIC CHEMISTRY CH3[CH2]4CH=CH.CH<^^°2H, m.p. 78° (A. 304, 117; 305, i). Methyl Ethyl Aticonic Acid, y-Ethylidene y-M ethyl Pyrotartaric Acid, i ,1-Dimethyl Vinyl Succinic Acid, (CH3)CH:C(CH8)CH<^Q2^O2H, m.p. 142°, is the chief product of reaction between methyl ethyl ketone and sodium ethoxide on succinic ester. Oxidation converts it into acetic acid and laevulinic acid (A. 321, 106). In indifferent solvents, the alkyl aticonic acids readily take up bromine. The dibromides, on losing HBr, change into the bromolactonic acids, which are con- verted by hydrogen into isoparaconic acids, and by boiling water, or when standing in alcoholic solution, into the neutral dilactones : HOCO CH2:C(CH 3)-CH HOCO.CH2 Dimethyl Aticonic Acid. Hoccn CH2Br.CBr(CH3).CH 3).C1 HOCO •CH2 CH2.C(CH3).CH O— CO.CH2 Isoheptodilactone. The formation of dilactones requires that each of the two doubly bound carbon atoms shall stand in the y-position to one of the two carbonyl groups (A. 304, 135). This shows the alkyl aticonic acids to be yS-unsaturated acids. It follows, there- fore, that one of the itaconic acids is theoretically not possible, since this acid lacks the 8 carbon atom. The aticonic acids can be looked on as being vinyl succinic acids, or can be derived from pyrotartaric acid, considerations which are indicated in the names given to the dimethyl aticonic acids. The dilactones, obtained from the aticonic acids through the bromolactonic acids, are converted by prolonged boiling in water into isomeric unsaturated lactonic acids, known as isaconic acids. Sodium amalgam converts them into isoparaconic acids, in the same way that the better known aconic acids give paraconic acids. Glutaeonie .Acid, CO2H.CH : CH.CH2.CO2H, m.p. 132°, is prepared from dicarboxylic glutaconic ester by hydrolysis with hydrochloric acid (A. 222, 249); from coumalic ester and barium hydroxide (A. 264, 301); from/?-hydroxyglutaric acid (p. 559), and sodium hydroxide solution (B. 33, 1452). It is isomeric with itaconic, citraconic, mesaconic and ethylidene malonic acids. - The zinc salt is deposited from its boiling solution ; ethyl ester, b.p. 237°, is most readily obtained by distillation of j8-acetoxyglutaric ester (p. 599)- Under certain conditions it polymerises to a di-molecular substance which, on hydrolysis, yields diglutaconic acid [C3H4(CO2H)2]?, m.p. 207°. This acid is also formed by hydrolysing the dimolecular isaconitic ester (q.v.), whilst the di-molecular glutaconic dicarboxylic ester (q.v.} yields a diglutaconic acid, m.p. 234° (B. 34, 675). When warmed with sodium ethoxide two molecules of glutaconic ester unite with the loss of alcohol, and there is formed dicarboxycyclohexenone acetic ester (B. 37, 2113, comp. C. 1903, I. 960). Glutaconic Anhydride, m.p. 82°, is formed when glutaconic and /?-hydroxy- glutaconic acids are heated (Kekutt); and from glutaconic acid and acetyl chloride p-rr pp» _ (m.p. 87°, B. 27,882); the imide, aa-Dioxy pyridine, CH^^^^NH or ' m.p. 183°, is formed (i) from glutaconaminic acid; (2) from glutaconamide, and (3) from /?-hydroxyglutaric amide, when these are heated with H2SO4 to 130—140°. Na and CH3I react with it to produce glutaconic methylimide ; with nitrous acid it gives rise to a nitroso-compound ; when distilled over zinc dust pyridine is formed : PC15 produces pentachloropyridine, C5C15N (see Constitution of Pyridine, Vol. II.). fi-Chloroglutaconic Acid, m.p. 129°, is prepared from acetone dicarboxylic acid and PC16 (p. 566 ; comp. glutinic acid, p. 523). Telrachloroglutaconic Acid, m.p. 109-110° (B. 26,2697). Homologous Glutaconic Acids. The alkylated glutaconic acids are best obtained by heating the acetyl compounds of the alkylated £-hydroxyglutaric acids, just as glutaconic acid itself from alkylated glutaconic acids (comp. C. I9°3, II- I.3I3). The CHg- group of the glutaconic ester is replaceable by alkyl groups by means HOMOLOGOUS GLUTACONIC ACIDS 521 of sodium or sodium alcoholate and iodoalkyls. It appears, therefore that the second carboxyl group exerts its influence on the methylene group across the ethylene group ; t /-*TT Jsf\^\-S n±\* and CHo-x./-/^ T> • ^vj2is. • ^L/u2Jt\. Glutaconic Ester. Malonic Ester. The reaction with C2H5ONa and CH3I not only converts glutaconic ester into aa-dimethyl glutaconic ester, but also produces ay -dimethyl glutaconic ester. Of this latter compound two desmotropic forms, I. and II. (see below) exist; further methylating of II. results in the production of aay-trimethyl glutaconic ester (C. 1903, 1. 1405) : I. RO2C.CH(CH3)— CH=CHCO2R and II. RO2C.C(CH3)=CH— CH2CO2R R02C.C(CH3)2— CH=CHC02R RO2C.C(CH,)=CH— CH(CH3)CO,R RO2C.C(CH8)=CH— C(CH3)2COaR The existence of the two desmotropic modifications HO 2C.CR = CH — CH 2CO 2H and HO2C.CHR — CH=CHCO2H is also demonstrated by the identity of the a/J- and j8y-dialkyl glutaconic acids, obtained by the following syntheses : sodium cyanacetic ester and acetoacetic ester produce sodium cyano-j8-methyl-glutaconic ester (i); CH3I converts this into a-cyano-aj8-dimethyl glutaconic ester (2), which by hydrolysis and loss of CO2 is changed into a^S-dimethyl-glutaconic acid (3). This substance is identical with the decomposition product of the con- densation of cyanacetic ester and a-methyl acetoacetic ester (4), which should be similar to j8y-dimethyl glutaconic acid (5) (C. 1906, I. 183) : CH3 CH3  The alkyl glutaconic acids show cis-trans isomerism. fi-Methyl Glutaconic Acid, Homomesaconic acid, HO2C.CH : C(CH3).CH2CO2H. Cis-form 147°, trans-form, n6&, is prepared from cyano-/?-methyl-glutaconic ester (see below); from carboxyl j8 -methyl glutaconic ester CO2R)2CH.C(CH3):- CHCO2R ; and from isodehydracetic acid (lactone of aci-acetyl ^-glutaconic mono- ester, CH3C(OH) : (CO2R).C(CH3) : CHCO2H) obtained by splitting the cis- and trans-forms. The cis-acid can be transformed into the trans-a,cid by boiling with strong alkali. The cis-acid forms an anhydride, m.p. 86° ; imide, m.D. 104.° (A. 345, 60). a/?- or py-Dimethyl Glutaconic Acid (see above), m.p. 148°, is formed by the method (3), above ; also from j8-methyl glutaconic ester by the action of sodium and iodomethane (A. 346, 117) ; anhydride, b.p.26 162° ; imide, m.p. 189°. aa-Dimethyl Glutaconic Acid, HO2C.C(CH3)2CH : CHCO2H, cis-form, m.p. 134° ; trans-form, m.p. 172°, is prepared from a-dimethyl glutolactonic acid (B. 33, 1920) ; from j8-hydroxy a-dimethyl glutaric acid ; from glutaconic ester, sodium and iodomethane ; some ay-Dimethyl Glutaconic Acid, m.p. 147°, is also formed (above) (C. 1903, II. 1315). aay-Trimethyl Glutaconic Acid, cis-form, m.p. 125°, trans-form, m.p. 150°, is formed from jS-hydroxy trimethyl glutaric acid and by methylating ay-dimethyi glutaric acid. The cis- acid gives rise to an anhydride, m.p. 88°. aap-Trimethyl Glutaconic Acid, cis-form, m.p. 133°, tracts-form, m.p. 148* 522 ORGANIC CHEMISTRY (C. 1903, II. 1315). afiy-Trimethyl Glutaconic Acid, m.p. 127° ; anlvydride, m.p. 119° ; imide, m.p. 180* (C. 1906, I. 185). Hydromuconic Acids. aj8-acid : COaH.CH2CH2CH=CHCO2H, m.p. 169°, stable form. 0y-acid : CO2H.CH2CH=CH.CH2CO2H, m.p. 195°, labile form. The labile acid is formed by the reduction of dichloromuconic acid or muconic acid (below), and of diacetylene carboxylic acid (p. 523). It dissolves with difficulty in cold water, and is oxidised to malonic acid by potassium per- manganate. When boiled with sodium hydroxide solution it is transformed into the stable acid, which is oxidised to succinic acid by permanganate. Sodium ' amalgam converts the labile acid into the stable form and reduces this to adipic acid (p. 505). Bichlorides and Dimethylene ester (C. 1901, II. 1119). a-Methylene Glutaric Acid, CH2 : C(COOH)CH2.CH2CO2.H, m.p. 129-130°, and a-Ethylidene $ -Methyl Glutaric Acid, CH3.CH : C(CO2H)CH(CH3)CH2CO2H, m.p. 129°. The esters of these acids are obtained by the polymerisation of acrylic and crotonic acids respectively (pp. 294, 295) by means of sodium alcoholate (B. 33, 3766 ; 34, 427). a-Methylene glutaric acid is also formed by the dis- tillation of a-methyl a-hydroxy valeric acid (B. 36, 1202). Suitable methods of reduction convert these acids into a-methyl glutaric acid and a-ethyl j3-methyl glutaric acids respectively. a-Ethylidene Glutaric Acid, CH3CH : C(COOH)CHaCH2CO2H, m.p. 152°, see 8-Caprolactone Carboxylic Acid (p. 560). Sodium hydroxide solution converts it into a- Vinyl Glutaric acid, CH2:CH.CH(CO2H)CH2CHaCO2H, m.p. 97° (B. 31, 2000). Isoamylidene Glutaric Acid, (CH3)2CHCH2CH : C(CO2H)CH2CH2CO2H, m.p. 15°, is formed together with diisovalerylidene glutaric acid (see below). Ally I Succinic Acid, CH2:CH.CH2CH(CO2H)CH2CO2H, m.p. 94°, is prepared from allyl ethylene tricarboxylic ester (B. 16, 333). Allyl Methyl- and Allyl- Ethyl Succinic Acid, see B. 25, 488. C. Diolenne Dicarboxylie Acids. Di ally I Malonic Acid, (CH2=CHCH2)2C(CO2H)2, m.p. 133°, with hydrobromic CH2.CH2.CH2.C.CH2.CH.2CH2 acid yields a dilactone, | /\ | . It breaks down into CO2 and diallyl acetic acid when heated (p. 306). Muconic Acid, CO2H.CH=CH-CH = CH.CO2H, m.p. 292°, with decomposi- tion, is formed when alcoholic potassium hydroxide acts on the dibromide of j3y-hydromuconic acid ; also, synthetically, from glyoxal and two molecules of malonic acid by means of pyridine ; dimethyl ester, m.p. 158° (B. 35, 1147). Di- chloromuconic Acid, C6H4C12O4, results when PClg acts on mucic acid (B. 24, R. 629). It yields jSy-hydromuconic acid with sodium amalgam (B. 23, R. 232). Dichloromuconic Acid Dichloride, and Dimethyl Ester (C. 1901, II. 1119). Isomeric muconic acids are not known. CHa:C.COOH Dimethylene Succinic Acid, may be considered as being the CH2:C.COOH parent substance of a large number of strongly coloured well-crystallising acids of the aromatic series (Vol. II.). It easily passes into a more deeply coloured anhydride, and exhibits a reversible difference of state in violet and ultra-violet light (p. 63). Therefore Stobbe named the hypothetical acid Fulgenic Acid (fulgere=tp shine) and the anhydride fulgide. The lesser known aliphatic fulgenic acids and fulgides are colourless (A. 359, i, etc.). Diisopropylidene Succinic Acid, aa$8-Tetramethyl Fulgtnic Acid, (CH8)2C:- C(COOH).CfCOOH) : C(CH,)2, m.p. 230° with decomposition, and Isopropylidene Isobutylidene Succinic Acid, acid-Dimethyl Isopropyl Fulgenic Acid, (CH3)2C:- C(COOH)C(COOH):CHCH(CH3)2, m.p. 226° with decomposition, result from the reaction of teraconic ester and acetone or isobutyl aldehyde respectively, with sodium ethoxide. The anhydrides, m.ps. 59° and 72°, are formed by means of acetyl chloride (B. 38, 3673, 3683). Diisovaleral Glutaric Acid, CH2[C(CO2H):CHCH2CH(CH3)a],, m.p. 220°, and is obtained from glutaric acid and isovaleraldehyde with acetic anhydride and sodium ethoxide or sodium (A. 282, 357). tRIHYDRIC ALCOHOLS 523 D. Acetylene and Polyacetylene Dicarboxylic Acids. Acetylene Dicarboxylic Acid, CO2H.C=C.CO2H-|-2H2O, m.p. 175° with decomposition, is obtained when aqueous or alcoholic potassium hydroxide acts on dibromo- and isodibromo-succinic acid (A. 272, 127). It effloresces on exposure. The anhydrous acid crystallises from ether in thick plates. The acid unites with the halogen acids to form halogen f umaric acids, whilst with bromine and iodine it yields dihalogen fumaric acids (p. 515). Its esters unite with bromine and form dibromomaleic esters and dibromofumaric esters (B. 25, R. 855). With water they yield oxalacetic ester (B. 22, 2929). They combine with phenyl- hydrazine and hydrazine, forming the same pyrazolone derivatives as oxalacetic ester (B. 26, 1719); and with diazobenzene imide they form phenyltriazole dicarboxylic ester (B. 26, R. 585). Oxalacetic ester and acetylene dicarboxylic ester are condensed by alcoholic potassium hydroxide to aconitic ester (B. 24, 127). (See also Acetoxymaleic Anhydride, p. 565.) The primary potassium salt, C4O4HK, is not very soluble in water, and when heated decomposes into CO2 and potassium propiolate (p. 303) ; silver salt breaks down readily into CO2 and silver acetylide (A. 272, 139); diethyl ester, b.p.15 145-148°, is obtained from dibromosuccinic ester with sodium ethoxide (B. 26, R. 706). (See also Thiophene Tetracarboxylic Esters.) Glutinic Acid, CO2H.C=C.CH2.CO2H, m.p. 145° with evolution of carbon dioxide, is obtained by the action of alcoholic potassium hydroxide (B. 20, 147) upon chloroglutaconic acid (p. 520). Diacetylene Dicarboxylic Acid, CO2H.C=C— C=C.CO2H+H2O, is made by the action of potassium ferricyanide on the copper compound of propiolic acid (B. 18, 678, 2269). It assumes a dark red colour on exposure to light, and at 177° explodes with a loud report. Sodium amalgam reduces it to hydromuconic acid, and at the same time splits it up into adipic and propionic acids. The ethyl ester , b.p.208 184°. Zinc and hydrochloric acid decompose it and yield propargylic ester (p. 303). Tetra-acetylene Dicarboxylic Acid,CO2H.C=C.C=C.C=C.C=C.CO2H. Carbon dioxide escapes on digesting the acid sodium salt of diacetylene dicarboxylic acid with water, and there is formed the sodium salt of diacetylene monocarboxylic acid, CH=C.C^CO2Na, which cannot be obtained in a free condition. When potassium ferricyanide acts on the copper compound of this acid, tetra-acetylene dicarboxylic acid is formed. This crystallizes from ether in beautiful needles, rapidly darkening on exposure to light and exploding violently when heated. Consult B. 18, 2277, for an experiment made to explain the explosibility of this derivative. V. TRIHYDRIC ALCOHOLS: GLYCEROLS AND THEIR OXIDATION PRODUCTS The trihydric alcohols, or glycerols, and their oxidation products are connected with the dihydric alcohols (glycols) and their oxidation products. The glycerols, so-called after their most important member, are obtained from the hydrocarbons by the substitution of three hydroxyl groups for three hydrogen atoms, linked to different carbon atoms. As the number of hydroxyl groups increases, the number of theoreti- cally possible classes of glycerols, in contrast to the glycols, also becomes greater. The number of possible classes of oxidation products also grows accordingly, and in the case of the trihydric alcohols this number is 19. However, this chapter of organic chemistry has been less regu- larly developed than that pertaining to the dihydric derivatives, and it may be said that the glycerols serve, even to a less degree than the glycols, as parent bodies for the preparation of the various classes 524 ORGANIC CHEMISTRY belonging here, some of which are : dihydroxymonocarboxylic acids, monohydroxydicarboxylic acids, diketone-monocarboxylic acids, tricar- boxy lie acids. Hydroxydialdehydes, hydroxydiketones, trialdehydes, aldehyde-diketones and triketones are represented to only a slight extent, if at all. The same may be said of the hydroxyaldehyde ketones, hydroxyaldehydic acids, hydroxyketonic acids, aldehyde-carboxylic acids, and aldehyde-ketone-carboxylic acids. i. TRIHYDRIC ALCOHOLS Glycerol stands at the head of this class, although it is not a tri- primary alcohol, but rather a diprimary-secondary alcohol. The simplest imaginable triprimary alcohol would have the formula CH- (CH2OH)3, and could be referred to trimethyl methane, CH(CH3)3, whereas glycerol is derived from propane, and considering the structure of the carbon nucleus, it is the simplest trihydric alcohol. Although it may appear unnecessary to develop all the possible kinds of trihydric alcohols and their oxidation products, as was done with the glycols, yet the oxidation products theoretically possible from glycerol will be deduced. By enlarging this scheme we really construct a comparative review of the oxygen compounds, obtainable from methane, ethane, and propane. It is also possible to tabulate the formulae of the oxygen derivatives of a hydrocarbon in such manner that the hydrogen atoms may be regarded as re- placed, step by step, by hydroxyl groups, and we may indicate the number of hydrogen atoms attached to one carbon atom, which have been replaced by hydroxyl groups.* Thus, in compounds containing more than one hydroxyl attached to the same carbon atom, numbers are employed to express the formulae of ortho- derivatives, usually only stable in the form of ethers. When a carbon atom of a hydrocarbon is joined to hydrogen, and no hydrogen atoms are replaced by hydroxyl, this is expressed by a zero : Methane  V VI oo 10 20 30 22 32 33 II 21 31 CH8 CH2OH CH(OH)a C(OH8) CH(OH)2 C(OH)3 C(OH), CH, CH, AH. CH3 CH(OH), CH(OH), C(OH), CH2.OH CH(OH)2 C(OH)3 CHa.OH CH2OH CH2OH * The author is indebted to A , J. Baeyer in Munich for indicating this method of exposition, " which has the great advantage of facilitating the derivation of the possible hydroxyl compounds from the higher hydrocarbons, and also to make apparent the degree of oxidation, i.e. the number of oxygen valencies which have entered." TRIHYDRIC ALCOHOLS 525 Propane = CH3.CH2.CH3=ooo ooo IOO OIO 2OO O2OJ no 101 3OO; 3IQ 32°: 3°3: 210 220: 302 j 321 120: 301 i 311 312: 201 202 i *2I2 222! Ill 211 i i2ij 322 323! The following formulae correspond with I : ooo CH3.CH2.CH3 zoo CH2OH.CH2.CH3 oio CH3.CHOH.CH3 II : 200 CH(OH)2.CH2.CH3 020 CH3C(OH)2CH3 no CH2OHCH.OH.CH3 101 CH2OH.CH2.CH2OH III : 300 C(OH)3.CH2.CH3 210 CH(OH)2.CH(OH)CH3 201 CH(OH)2CH2.CH2OH 120 CH2OH.C(OH)2CH3 in CH2OH.CHOH.CH2OH IV : 310 C(OH)3.CHOH.CH3 301 (COH)3.CH2.CH2OH 220 CH(OH)2.C(OH)2.CH3 202 CH(OH)2.CH2.CH(OH)2 211 CH(OH)2.CH.OH.CH2OH 121 CH2OH.C(OH)2.CH2OH V: 320 C(OH)3.C(OH)2.CH3 302 C(OH)3.CH2.CH(OH)2 311 C(OH)3.CHOH.CH2OH 221 CH(OH)2.C(OH)2.CH2.OH 212 CH(OH)2.CH(OH).CH(OH)2 VI : 303 C(OH)3.CH2.C(OH)3 321 C(OH)3.C(OH)2.CH2OH 312 C(OH)3.CHOH.CH(OH)2 222 CH(OH)2.C(OH)2.CH(OH)2 VII : 322 C(OH)3.C(OH)2.CH(OH)2 313 C(OH)3.CH(OH).C(OH)3 VIII : 323 C(OH)3.C(OH)2.C(OH)3 these groups of numbers : Propane n-Propyl Alcohol Isopropyl Alcohol Propionic Aldehyde Acetone Propylene Glycol Trimethylene Glycol Propionic Acid Unknown (pp. 336, 340) jS-Hydroxypropionic Aldehyde Hydroxyacetone, Ketol Glycerol Lactic Acid Hydracrylic Acid Pyroracemic Aldehyde Malonic Dialdehyde (p. 347) Glycerose Dihydroxyacetone Pyroracemic Acid Formacetic Acid Glyceric Acid Unknown Unknown Malonic Acid Hydroxypyroracemic Acid (p. 543) Tartronic Semialdehyde (p. 543) Mesoxalic Dialdehyde Unknown Tartronic Acid Mesoxalic Acid Of the 29 possible hydroxyl substitution products of propane indicated in the above tables by numbers, five are underlined, n-propyl alcohol, isopropyl alcohol, propylene glycol, trimethylene glycol and glycerol. The remaining 24 can be looked on as being oxidation products of these. The dotted line connects these products with the parent substance. Two are derivable from n-propyl alcohol, one from isopropyl alcohol, five from propylene glycol and from trimethyl- ene glycol ; eleven from glycerol. The following table shows them rearranged according to their usual formulae — that is, their ortho-formulae minus water : CH2OH CH.OH CH2OH (in) Glycerol. CHO C02H CH2OH CHO C02H CO2H CHOH CHOH "l° CO CHOH CH2OH CH2OH 1° CH2.OH CH2.OH CH2.OH CHO (211) (311) (l2l) (221) (321) ^312; Glyceric Glyceric Acid. Dihydroxy- Unknown. Hydroxypyro- Tartronic Aldehyde. acetone. racemic Acid. Semialde- hyde. 526 ORGANIC CHEMISTRY CHO C02H CHO C02H CO2H CHOH CHOH CO CO C(OH)a CHO C02H CHO CHO CO2H (212) (313) (222) (322) (323) Unknown. Tartronic Acid. Mesoxalic Di- Mesoxalic Semi- Mesoxalie aldehyde. aldehyde. Acid. Glyceric acid, tartronic acid, and mesoxalic acid are the only accurately known representatives of these eleven oxidation products of glycerol. Glyceric aldehyde, dihydroxyacetone, hydroxyacemic acid, tartronic semialdehyde, mesoxalic di- and semi- aldehydes have all been investigated to only a small extent. Three hydrogen atoms in glycerol can be replaced by alcohol or acid radicals, producing ethers and esters : (OH (OH (O.C2H3O C3HXOH C3HXO.C2H30 C3H5{ O.C2H3O (O.C2H30 (O.C2H30 (O.C2H30 Acetin. Diacetin. Triacetin. The haloid esters are the halohydrins : C,H5(OH)aCl C3HB(OH)C12 C3H6C13 Monochlorhydrin. Dichlorhydrin. Trichlorhydrin. Formation. — The trihydric alcohols are obtained (i) by heating the bromides of the unsaturated alcohols with water ; or — (2) By oxidizing the unsaturated alcohols with potassium per- manganate (B. 28, R. 927). (3) Aldehydes having the constitution RCH2CHO condense with formaldehyde in the presence of lime to form triprimary glycerols : RCH2CHO + 3CH20+H20=RC(CH2OH)2CH2OH+HCOOH. (4) Dialkyl ethers of glycerol are prepared by the magnesium organic synthesis from carboxylic esters or alkoxyketones and chloro- or iodo-substituted ethers. Glycerol [Propanetriol], CH2OH.CHOH.CH2OH, m.p. 17° (solidifies below o°), b.p.760 290° almost without decomposition, b.p.12 170°, D15= 1*265, is produced (i) in small quantities in the alcoholic fermentation of sugar ; hence is contained in wine (p. 114). (2) It is prepared by hydrolysis of oils and fats, which are glycerol esters of the fatty acids. Glycerol is also formed (3) from synthetic allyl trichloride by heating it with water, and (4) from allyl alcohol when it is oxidized with potassium permanganate. (5) Also, by the reduction of dihydroxyacetone. Historical. — Scheele discovered glycerol in 1779, when he saponified olive oil with litharge, in making lead plaster. Chevreul, who recognized ester-like derivatives of glycerol in the fats and fatty oils, introduced the name glycerol, and in 1813 pointed to similarities between it and alcohol. The composition of glycerol was established in 1836, by Pelouze. Berthelot and Lucca (1853), and later Wurtz (1855), explained its constitution, and proved that it was the simplest trihydric alcohol, the synthesis of which Friedel and Silva (1872) effected from acetic acid : C02H CH3 CHa CH3 CH3 CH2C1 CH2OH CH 41 <W, -< CH, CH3 CH2 CH2C1 CHjCl CH2OH GLYCEROL 527 (i) Acetone is obtained from calcium acetate. (2) Acetone by reduction passes into isopropyl alcohol. (3) Propylene results when anhydrous zinc chloride withdraws water from isopropyl alcohol. (4) Chlorine and propylene yield propylene chloride. (5) Propylene chloride and iodine chloride unite to form propenyl trichloride or allyl trichloride, the trichlorhydrin of glycerol. (6) Glycerol is produced when trichlorhydrin is heated with much water to 160° (B. 6, 969). Metallic iron and bromine convert propylene bromide into tri- bromhydrin, which silver acetate changes to triacetin. Bases saponify the latter and glycerol results (B. 24, 4246). A second method of synthesizing glycerol is that of 0. Piloty (1897), which starts from L. Henry's nitro-tert.-butyl glycerol, the condensation product of formaldehyde and nitromethane. (i) Nitro-tert.-butyl glycerol is reduced to hydroxylamino-tert. -butyl glycerol, which is then (2) oxidized by HgO to di- hydroxyacetone oxime : (CH2OH)3C.NH(OH)+20 = (CH2OH)2C:NOH+HC02H+H20; (3) bromine water converts this substance into dihydroxy-acetone : 2(CH2OH)2C : NCH + 2Br2+H2O=2(CH2OH)2C : O+N2O+4HBra ; which, finally, is reduced to glycerol by sodium amalgam (B. 30, 3161) : CH2OH /CH2OH /CH2OH (i) NO2.C(-CH2OH > (2) NH(OH).C^-CH2OH > (3) C=NOH > \CH2OH \CH2OH CH2OH CH2OH CH2OH CO -•> (4) CHOH 2OH CH2OH Preparation. — Glycerol is produced in large quantities during the saponifica- tion of fats and oils in soap and candle manufacture. When the process is carried out with superheated steam, an aqueous solution of glycerol and free insoluble fatty acids are formed. Pure glycerol is produced from its solution by distillation under reduced pressure. Properties. — Anhydrous glycerol is a thick, colourless syrup, which slowly solidifies at o°, forming transparent crystals. With superheated steam it distils entirely unaltered. It has a pure, sweet taste, hence the name glycerol, and it is very , hygroscopic, mixing in every pro- portion with water and alcohol. It is fairly soluble (i : 3) in acetone (A. 335, 319), but insoluble in ether. It dissolves the alkalis, alkali earths and many metallic oxides, forming with them, in all probability, metallic compounds similar to the alcoholates (p. 116) . Copper Sodium Gly cerate, (CsHsOsCuNa^+sH^O, is obtained from glycerol, copper oxide and sodium hydroxide solution (B. 31, 1453). Reactions. — (i) When glycerol is distilled with dehydrating sub- stances, like sulphuric acid and phosphorus pentoxide, boric acid, or preferably potassium hydrogen sulphate, it decomposes into water and acrolem (p. 214). (2) When heated to 430-450°, glycerol decomposes partly into acrolem and partly into acetol : CH2:CH£HO -<^°CH2(OH).CH(OH).CHa(OH) — *-> CH,.CO.CH2OH (comp. transformation of glycols into aldehydes and ketones, p. 312) ; the acetol partially decomposes into acetaldehyde and formaldehyde 528 ORGANIC CHEMISTRY which, like acrolein itself, unite with glycerol to form acetal-like substances (A. 335, 209). (3) When sodium glycerol or glycerol and sodium hydroxide are heated together, hydrogen is evolved and mainly lactic acid is formed, together with lower fatty acids, methyl alcohol and propylene glycol (A. 335, 279). (4) Platinum black and air, mercuric oxide and alkali or dilute nitric acid convert glycerol into glyceric and tartronic acids ; sodium and bismuth nitrate oxidize it to mesoxalic acid (B. 27, R. 666). Energetic oxidation produces oxalic, glycollic and glyoxylic acids (p. 400) ; silver oxide gives rise to formic and glycollic acids (A. 335, 316). (5) Moderated oxidation (with nitric acid or bromine) produces glycerose, which consists chiefly of glyceraldehyde and dihydroxyacetone, CO(CH2.OH)2. This unites with HNC and forms trihydroxybutyric acid : CHO CH2OH CH20*H C02H CO2H CO2H CHOH CO -<— - CH.OH - -> CH.OH — > CH.OH C(OH)2 CH2.OH CH2OH CH2.OH CH2OH C02H C02H Glyceral- Dihydroxy- Glycerol. Glyceric Tartronic Mesoxalic dehyde. acetone. Acid. Acid. Acid. (6) Phosphorus iodide or hydriodic acid converts it into allyl iodide, isopropyl iodide, and propylene (p. 104). (7) In the presence of yeast at 20-30° it ferments, forming propionic acid. By Schizomyceles fermentation, induced by Butyl bacillus (B. 30, 451 ; 41, 1412), normal butyl alcohol (p. 118), trimethylene glycol and formic and lactic acids result (p. 314). (8) When glycerol is distilled with ammonium chloride, ammonium phos- phates and other ammonium salts, /J-picoline (Vol. II.), as well as 2,5-dimethyl pyrazine (Vol. II.), results. Under certain conditions it is only the latter which is produced (24, 4105 ; B. 26, R. 585 ; 27, R. 436, 812 ; A. 335, 223). Uses. — Glycerol is applied as such in medicine. It is also used in gas meters. Duplicating plates and hectographs consist of mixtures of gelatin and glycerol. The bulk of glycerol is consumed in the manufacture of nitro- glycerine (p. 529). Glycerol Homologues.— 1,2,3-Butyl Glycerol, CH3.CH(OH).CH(OH).CH2OH, b.p.27 172-175°, is prepared from crotonylalcohol dibromide (p. 124). [1,2,3-Pentanetriol], C2H5.CH(OH).CH(OH).CH2.OH, b.p.63 192° ; [2,3,4- Pentanetriol], CH3.CH(OH).CH(OH).CH(OH).CH3, b.p.27 180°; p -Ethyl Glycerol, CH3.CH2C(OH)(CH2OH)2> b.p.68 186-189°. These and other glycerols result upon oxidizing unsaturated alcohols with potassium permanganate (B. 27, R. 165 ; 28, R. 927). Pentaglycerol, CH3C(CH2OH)3, m.p. 199°, is obtained by the action of lime on propyl aldehyde and formaldehyde (A. 276, 76). Dimethyl Pentaglycerol, (CH3)2CHC(CH2OH)3, m.p. 83°, 'is prepared from iso- valeraldehyde and formaldehyde by the action of lime (B. 36, 1341). These substances are triprimary glycerols. {T.,4,5-Hexanetrior\, CH3.CH(OH).CH(OH).CHa.CH2.CH2OH, b.p.10 181°, and some other isomers and higher homologues have been obtained from the addition products of bromine and hypochlorous acid with the corresponding unsaturated alcohols. GLYCEROL ESTERS OF INORGANIC ACIDS 529 A. GLYCEROL ESTERS OF INORGANIC ACIDS (a) Glycerol Haloid EstTS. — These are called halohydrins (p. 124). There are two possible isomeric mono- and di-halohydrins. They are distinguished as a-halohydrins and /?- halohydrins : CH2C1 CH2OH CHaCl CH2OH CHOH CHC1 CHOH CHC1 CH2OH CH2OH CH8C1 CH2C1 o-Chlorhydrin. /3-Chlorhydrin. «-Dichlorhydrin. /3-Dichlorhydrin. The monohalohydrins may also be regarded as halogen substitution products of propylene and trimethylene glycol, whilst the dihalohydrins are probably the dihalogen substitution products of propyl and isopropyl alcohol (p. 117). a-Monohalohydrins are formed when the halogen acids act on glycerol, and by the interaction of water and epihalohydrins. a-Chlorhydrin, CH2OH.CHOH.CH2C1, b.p.18 139°. a-Bromhydrin, b.p.10 180°. a-Iodohydrin, b.p.24 62° (A. 335, 237). p-Chlorhydrin, CH2OH.CHC1.CH2OH, b.p.lg 146°, is obtained from allyl alcohol andClOH (C. 1897, I. 741). a-Dihalohydrins are produced when the halogen acids (A. 208, 349) act on glycerol, and on the epihalohydrins (p. 532) (B. 10, 557). Potassium iodide changes the chlorine derivative into the iodine compound. a-Dichlorhydrin, CH2C1.CHOH.CH2C1, b.p. 174°, D19 = i'367, is a liquid, with ethereal odour. It is not very soluble in water, but dissolves readily in alcohol and ether. When heated with hydriodic acid it becomes converted into isopropyl iodide ; sodium amalgam produces isopropyl alcohol. When sodium acts on an ethereal solution of a-dichlorhydrin, we do not get trimethylene alcohol, but allyl alcohol as a result of molecular transposition (B. 21, 1289). Chromic acid oxidizes it to ^S-dichloracetone (p. 224) and chloracetic acid. Potassium hydroxide converts it into epichlorhydrin (p. 532). a-Dibromhydrin, CH2Br.CHOH.CH2Br, b.p. 219°; D1?=2-ii. a-Di-iodhydrin, 0=2-4, solidifies at —15°, is a thick oil. It readily loses HI and polymerizes to fi-iodopropionaldehyde (C. 1900, II. 169). fi-Ethyl a-Dichlorohydrin, C2H6C(OH)(CH2C1)2, b.p.18 77°, is formed from sym.- dichloracetone and ethyl magnesium bromide (C. 1906, I. 1471). The £-Dihalohydrins result from the addition of halogens to allyl alcohol. fl-Dichlorhydrin, b.p. 183°, D0=i'379, is converted by sodium into allyl alco- hol. Hydriodic acid changes it to isopropyl iodide ; fuming nitric acid oxidizes it to a/?-dichloropropionic acid. Both dichlorhydrins are changed to epichlorhydrin by alkalis. fi-Dibromhydrin, b.p. 212—214°. Trihalohydrins are formed when halogens are added to the allyl halides; also in the action of phosphorus halides on the dihalohydrins, and when iodine chloride acts on propylene chloride, and bromine and iron on propylene bromide and trimethylene bromide (B. 24, 4246). Trichlorhydrin, Glyceryl Chloride, 1,2,3-Trichloropropane, CH2C1.CHC1.CH2C1, b.p. 158°. Tribromhydrin, m.p. 16°, b.p. 220°, is converted by silver acetate into glycerol triacetyl ester. When this is saponified it yields glycerol (p. 527). (b) Glycerol Esters of the Mineral Acids containing1 Oxygen. — The neutral nitric acid ester (nitroglycerol) — nitroglycerine (discovered by Sobrero in 1847) — is the most important member of this class. Nitroglycerine, Glycerol Nitrate, CH2(ONO2).CH(ONO2).CH2(ON92), m.p. 16°, D = i-6, is produced by the action of a mixture of sulphuric and nitiic acids on glycerol. The latter is added, drop by drop, to a well-cooled mixture of two parts of fuming nitric acid and three parts of concentrated sulphuric acid. On standing the nitroglycerol rises, and, after separation, is poured into water. VOL. I. 2 M 530 ORGANIC CHEMISTRY The heavy oil (nitroglycerine) is washed with water and dried by means of calcium chloride. Nitroglycerine is a colourless oil, which is easily volatilized at 160° (15 mm. pressure) (B. 29, R. 41). It has an acrid taste, and is poisonous when taken internally. It is sparingly soluble in water, dissolves with difficulty in cold alcohol, but is easily soluble in wood spirit and ether. Heated quickly, or upon percussion, it explodes very violently ; mixed with kieselguhr it forms dyna- mite, and with nitrocellulose, smokeless powder. Alkalis convert nitroglycerine into glycerol and nitric acid ; ammonium sulphide also regenerates glycerol. Both reactions prove that nitroglycerine is not a nitro-compound, but a nitric acid ester. Partial nitration of glycerol or partial hydrolysis of nitroglycerine by dilute sulphuric acid produces the two possible dinitroglycerines, C3H6(OH)(ONO2)2, oils, which are not explosive; and also the two mononitroglycerines, C3H5(OH)2- (ONO)2, m.ps. 59° and 54° ; these substances are easily soluble in water (B. 41, 1107). Glycerol Nitrite, C3H5(O.NO)8, is formed by the action of N2O3 on glycerol. It is isomeric with trinitropropane (B. 16, 1697). Glycerol Sulphuric Acid, CHaOH.CHOH.CH2.OSO3H, is obtained from glycerol and sulphuric acid. Propane-i.z^-trisulphonicAcid, C3H6(SO2H)3, how- ever, is formed from tribromhydrin and ammonium sulphite (C. 1904, II. 944). Glycerol Phosphoric Acid, C3H6<o>po*H ' occurs combined with the fatty acids and choline as lecithin (p. 531) in the yolk of eggs, in the brain, in the bile, and in the nerve tissue. It is produced on mixing glycerol with metaphosphoric acid. The free acid is a thick syrup, which decomposes into glycerol and phos- phoric acid when it is heated with water. It yields easily soluble salts with two equivalents of metal. The calcium salt is more insoluble in hot than in cold water ; on boiling its solution, it is deposited in glistening leaflets (C. 1899, 1. 1 105). For mono-acidic and neutral glycerol phosphate, C3H5.O3PO, see C. 1904, I. 431. For the action of PCI, on glycerol, see C. 1902, I. 1048. Glycerol mercaptans are produced when chlorhydrins are heated with alcoholic solutions of potassium hydrosulphide. B. GLYCEROL FATTY ACID ESTERS, GLYCERIDES (a) Formic Acid Esters. Monoformin, C8H6(OH)2OCHO, is volatile under diminished pressure. It is supposed that it is formed on heating oxalic acid and glycerol. When it is heated alone it breaks down into allyl alcohol (p. 123), water, and carbon dioxide. Diformin is1 most certainly produced under these conditions. Monoformin also results from the action of d-monochlorhydrin on sodium formate. Diformin, C3H5(OH).(O.CHO)2, b.p.20_30 163-166°. (b) Acetic Esters, or Acetins, result when glycerol and acetic acid are heated together (C. 1897, II. 474). Monacetin, b.p.2_3 131°. Diacetin, C3H5(O.COCH3)2- (OH), b.p. 159° (B. 25, 3466). Triacetin, C3H6(O.COCH3)3, b.p. 258°, occurs in small quantities in the seed of Euonymus europceus, and has also been obtained from tribromhydrin (p. 529). Dichloromonacetin and monochlorodiacetin (C. 1905, I. 12). (c) Tributyrin, C3H5(OC4H7O)3, b.p.10 185° (C. 1899, II. 21 ; 1900, II. 215), occurs in cow's butter (p. 259). (d) Glycerides of Higher Fatty Acids occur, as already stated (p. 264), in the vegetable and animal fatty oils, fats, and tallows. They can be artificially obtained by heating glycerol with the fatty acids (C. 1899, II. 20), or from tri- bromhydrin and fatty acid salts (C. 1900, II. 215). The mono- and di-esters (monostearin, dipalmitin, etc.) are prepared from mono- or di-chlorhydrins and salts of the fatty acids, or by esterifying glycerol and the fatty acids by means of concentrated sulphuric acid (C. 1903, I. 133 ; B. 38, 2284). If esterification is completed with different acids mixed glycerides, such as palmitodistearin, are formed, which occur to a certain extent in natural fats (B. 36, 2766). Glycerides are very slightly soluble in cold alcohol, but easily so in ether. They are saponified by alkalis or lead oxide (comp. p. 264) (C. 1899, II. 1699). GLYCEROL ETHERS 531 When boiled with alcohols in presence of a little alkali or acid, the glycerides are, to a great extent, converted into glycerol and fatty esters of the alcohols (C. 1907, I. 151 ; 1908, I. 1157 ; II. 495). The most important glycerides are : Trimyristin, or Myrislin, Glycerol Myristic Ester, C3H5(O.C14H27O)3, m.p. 55°, occurs in spermaceti, in nutmeg butter, and chiefly in oil nuts (from Myristica surinamensis), from which it is most readily obtained (B. 18, 201 1 ). It crystallizes from ether in glistening needles. It yields myristic acid (p. 261 ) when saponified. Tripalmitin, C3H5(O.C1<5H31O)8, m.p. (45°) 65°, is found in most fats, especially in palm oil ; it can be separated from olive oil at low temperatures. Tristearin, C3HS(O.C18H35O)3, m.p. (55°) 71-5°, occurs mainly in solid fats (tallows). It can be obtained by heating glycerol and stearic acid to 280—300°. It crystallizes from ether in shining leaflets. On the phenomenon of the " double melting-point " of palmitin and stearin, see C. 1902, I. 1196. Triolein, or Olein, C3H5(O.C1SH33O)3, solidifies at —6°. It is found in oils, like olive oil. It is oxidized on exposure to the air. Nitrous acid converts it into theisomeric elaidin, m.p. 36° (p. 301). Lecithins are widely distributed in the animal organism and occur especially in the brain, in the nerves, the blood corpuscles, and the yolk of egg, from which stearin-palmitic lecithin is most easily prepared. Lecithin occurs in the seeds of plants (B. 29, 2761). It is a wax-like mass, easily soluble in alcohol and ether, and crystallizes in fine needles. It swells up in water and forms an opalescent solution, from which it is reprecipitated by various salts. It units with bases and acids to salts, forming a sparingly soluble double salt, (C42H84NPO8.HC1)2.- PtCl4, with platinic chloride. Lecithin is decomposed into choline, glycero- phosphoric acid (see above), stearic acid, and palmitic acid, when it is boiled with acids or barium hydroxide solution. Therefore we assume it to be an ethereal compound of choline with glycerophosphoric acid, combined as glyceride with stearic and palmitic acids : CH2— O.COC17HS$ CH— O.COC16HS1 (CH3)3v. ^ nT» CH2— O.PO(OH).O.CH2CH2>jN Lecithin is optically active — dextro-rotatory. When heated in alcoholic solution to 90-100° it is racemized, and from this i-lecithin, \-lecithin can be separated by lipase (C. 1901, II. 193 ; 1906, II. 493)- The distearin and dioleo- compounds are also known. Protagon, a substance obtained from the brain, appears to be closely related to the lecithins. Glycerol Ethers : i. Alkyl Ethers. Mixed ethers of glycerol with alcohol radicals are obtained by heating the mono- and dichlorhydrins with sodium alcoholates. Epichlorhydrin, sodium hydroxide solution, and an alcohol form glycerol dialkyl ether (C. 1898, I. 237). Monoethylin, CH2OH.CHOH.CH2OC2H6, b.p. 230°, is soluble in water. Glycerol Dimethyl Ether, b.p. 169°. Diethylin, CH2OH.CH(OC2H5)CH2OC2H5, b.p. 191°, dissolves with difficulty in water, and has an odour resembling that of peppermint. Triethylin, C3H6(OC2H5)3, b.p. 185°, is insoluble in water. Allylin, CH2OH.CHOH.CH2C3H5, b.p. 225-240°, is produced by heating glycerol with oxalic acid (B. 14, 1946, 2270), and is present in the residue from the preparation of allyl alcohol (p. 123). It is a thick liquid. Diallylin, HO.C8H5(OC3H5)2, b.p. 225°-227, is produced when sodium allylate acts on epichlorhydrin (B. 25, R. 506). Dialkyl Ethers of Homologous Glycerols. Fatty acid esters are condensed with chloromethyl alkyl ethers to form dialkyl ethers of homologous glycerols by means of magnesium, which can be rendered more active by means of HgCl2 (C. 1907, I- 8?1) : RCOOC2H6+2ClMgCH2OC2H6 > RC(OH)(CH2OC2H5)2. These diethylines yield acrole'ins, similarly to glycerol itself, when treated 532 ORGANIC CHEMISTRY with oxalic acid : two molecules of alcohol are eliminated and o-alkyl acroleins result (comp. p. 214). Ethyl Glycerol Diethyl Ether, C2H6C(OH)(CH2OC2H6)2, b.p. 195°, is prepared from propionic ester, chloromethyl ethyl ether and magnesium. Propyl Glycerol Diethylin, b.p. 210°; the Isobutyl, b.p. 215°; n-Amyl, b.p.13 119°; Hexyl, b.p.,6 136° ; Octyl, b.p.16 160° ; Decenyl Glycerol Dimethylin, b.p.12 180°. i,7-Dimethoxyheptane-4-ol, HC(OH)[CH2CH2CH2OCH3]2, b.p. 247°, is pre- pared from formic ester, y-methoxypropyl iodide and magnesium. It is a liquid possessing a very bitter taste (C. 1906, I. 332). 2. Cyclic Ethers : /CH2.O.CH2x / Glycerol Ether, CH^ O ^CH or CH, /OCH, b.p. 171°, is ,CHt— O.CH2 — ^j V/V/J.J. VJ. VsJLJLg V^V^V^XX, \CH2.O.CH/ \ / I \CH — OCH2 formed when glycerol is heated to 270-330°, with a little ammonium chloride (A. 335, 209) ; also, together with diallylin, from epichlorhydrin and sodium allylate (see above). It is readily soluble in water, and is hydrolyzed with difficulty. An isomeric substance, m.p. 124°, has been obtained as a by-product of the preparation of pyridine bases from glycerol and ammonium phosphate (comp. p. 528) (C. 1897, I. 583)- Glycerol derivatives resemblingthe acetalsare formed when formaldehyde, acet- aldehyde, acrolem, benzaldehyde, or acetone act on glycerol hot, or in presence of /O.CH, /O.CH2X hydrochloric acid. Formal Glycerol, CHS \ orCHj/ >CHOH, XO.CH.CH2OH XO.CH/ b.p. 193° (A. 289, 29 ; 335, 209). Acetal Glycerol, HOC8H6O2>CHCH3, b.p.18 86*. a-Acrolefn Glycerol, HO.C3H5O2>CH.CH:CH2, is isomeric with glycerol ether or j3-acrolem glycerol (q.v.). Benzal Glycerol, HOC3H6O2>CHC6H5, m.p. 66°. Acetone Glycerol, HOC3H6O2>C(CH3)2, b.p.n 83° (B. 27, 1536; 28, 1169). XCH.CH2OH Glycide Compounds: Glyeide, Epihydrin Alcohol, Oc | , b.p. 162°, CH2 D0=i'i65, is isomeric with acetyl carbinol (p. 341). This body shows the properties both of ethylene oxide and of ethyl alcohol. It is obtained from its acetate by the action of sodium hydroxide or barium hydroxide. Glycide and its acetate reduce ammoniacal silver solutions at ordinary temperatures. Glycerol also forms polyglycerols. Thus glycerol yields Diglycerol, (HO)2.C3- H6OC3H6(OH)2, when it is treated withchlorhydrin or aqueous hydrochloric acid at CH2— O — CH CH2OH 130°. The polymer of glycide, Diglycide • • (?), JtlU — L<rl o — l^rl — -U — UJrl 2 results from the action of sodium acetate on epichlorhydrin in absolute alcohol, and the subsequent hydrolysis of diglycide acetate with sodium hydroxide. XCH.CH2C1. Epichlorhydrin, O<; b.p. 117°, Dt=i*203, is isomeric with mono- chloracetone, and constitutes the parent substance for the preparation of the glycide compounds. It is obtained from both dichlorhydrins by the action of alkali hydroxides (analogous to the formation of ethylene oxide from glycol chlorhydrin) (p. 319) : C1CH2.CHOH C1CH2.CH x C1CH.CH2C1 I -- •> I CH2C1 CH HOCH2 It is a very mobile liquid, insoluble in water. Its odour resembles that of chloroform, and its taste is sweetish and burning. It forms a-dichlorhydrin with concentrated hydrochloric acid. PC16 converts it into trichlorhydrin. Con- tinued heating with water to 180° changes it to a-monochlorhydrin. Con- centrated nitric acid oxidizes it to j8-chlorolactic acid. Metallic sodium converts it into sodium allylate, CH?=CH,CH,ONa, DIHYDROXY-ALDEHYDES 533 Like ethylene oxide, epichlorhydrin combines with HNC to the hydroxy- Epibromhydrin, C3H5OBr, b.p. 130-140°, is prepared from the dibrom- hydrin. Epi-iodohydrin, C3H6OI, b.p.12 62°, is prepared from epichlorhydrin by the action of KI and alcohol, and subsequent treatment with aqueous alkali hydroxides. Epihydrin-ether, [O<C3H6]2O, b.p.22 103°, is produced from the above by means of silver oxide ; and Nitroglycide, NO2.OC3H5>O, b.p.15 63°, by silver nitrate. It also results when alkali acts on either of the two. dinitroglycerols (p. 530) (A. 335,238; B. 41, 1117). Di-epi-iodohydrin, ICH2.CH/°~^aNcH.CH2I, m.p. 160°, is formed when iodine acts on mercury allyl alcohol iodide, (C3H5O.HgI)2. This body, as well as mercury propylene-glycol iodide, IHg.CHaCH(OH)CH2OH, is also obtained from allyl alcohol and mercury salts (comp. Mercury Ethanol Iodide, p. 326) (6.34,1385,2911). Epiethylin, Ethyl Glycide Ether, O<C8H6.OCaH6, b.p. 129°, and Amyl Glycide Ether, b.p. 188°, are produced from the respective ethers of chlorhydrin by distillation with potassium hydroxide (A. 335, 231). Glycide Acetate, O<C8H6.OCOCH3, b.p. 169°, is formed from epichlorhydrin and anhydrous potassium acetate. Nitrogen Derivatives of the Glyeerols. 