None
3o4 ORGANIC CHEMISTRY Tetrollc Acid, Methyl Acetylene Car- M P. B. P boxylicAcid , CH3C=C.C02H 76° 203° Ethyl Acetylene Carboxylic Acid . . . CH3.CH2.C=c.COaH 80° n-Propyl Acetylene Carboxylic Acid . CH3.CH2.CHa.CEEC.COaH 27° 125° (20 mm.) Isopropyl Acetylene Carboxylic Acid . . (CH3)2CH.C=EC.CO2H 38° 107° (20 mm.) n-Butyl Acetylene Carboxylic Acid . . CI 1 3.[CH2]3CEEC.CO2H liquid 136° (20 mm.) tert. Butyl Acetylene Carboxylic Acid . . (CH3)3C.C=C.COaH 48° no0 (10 mm.) Amyl Propiolic Acid C5HUC^C.CO2H 5° 149° (20 mm.) Hexyl Propiolic Acid C6H13C=C.CO2H -10° 155° (18 mm.) Heptyl Propiolie Acid C7H15C=EC.CO2H 6-10° 166° (20 mm.) Nonyl Propiolic Acid C9H18C=C.CO2H 30° Tetradecyl Propiolic Acid CH3[CH2]13OEEC.CO2H 44° Of these, Tetrolic Acid has been the most thoroughly investigated, and is obtained from j3-chlorocrotonic acid and /3-chlorisocrotonic acid when these are boiled with potassium hydroxide (A. 345, 103). At 210° the acid decomposes into CO a and allylene, C,H4 (B. 27, R. 751). Potassium permanganate oxidizes it to acetic and oxalic acids. It combines with HC1 and HBr, forming jS-chloro- crotonic acid and /?-bromocrotonic acid (B. 22, R. 51 ; 21, R. 243). With bromine, in sunlight, it yields dibromocrotonic acid, m.p. 120°, whereas in the dark the halogen produces the isomeric dibromocrotonic acid, m.p. 94° (B. 28, 1877 ; 34, 4216). aaj8-Trichlorobutyric acid (p. 289), upon the loss of HC1, yields two dichlorocrotonic acids, m.p. 75° and 92° (B. 28, 2665). These two acids are also produced when chlorine acts on tetrolic acid. Tetrolic Ethyl Ester, b.p. 164°, forms the amide, m.p. 148°, with ammonia, together with )5-aminocrotonic ester. An aqueous solution of the amide, when heated with mercuric chloride, becomes hydrated, forming acetoacetic amide : CH3C==CCONH2 > CH8CO.CHaCONH,, Phenylhydrazine forms the tetrolic ester, phenyl methyl pyrazolone ; diazoacetic ester produces a pyrazole derivative (A. 345, 100). Several higher homologues of propiolic acid have been prepared by the action of alcoholic potassium hydroxide on the brom-addition products of the higher define monocarboxylic acids (p. 300). Undecolic Acid, CH,C:C[CH2]7CO2H, m.p. 59°, is obtained from undeclyenic acid (p. 299). By oxidation, azelaic acid is formed (B. 33, 3571). Isomeric with it is dehydro-undecylenic acid (p. 299). Stearolic Acid, C8H17CiC[CH2]7CO2H, m.p. 48° (constitution, see p. 300), is obtained from oleic and ela'idic acids. Behenolic Acid, C22H40O2, m.p. 57'5° (constitution, see p. 300), from the bromides of erucic and brassidic acids (B. 24, 4116 ; 26, 640, 1867). On warm- ing the last two acids with fuming nitric acid they yield the monobasic acids : stearoxylic, or g,io-diketostearic acid, CH3[CH2]7CO.CO[CH2]7CO2H, m.p. 86°, and behenoxylic, or i^,i^-dikeiobehenic acid, CH3[CH2]7CO.CO.[CH,]11CO2H, m.p. 96° (B. 28, 276). Sulphuric acid converts stearolic acid into ketostearid acid, and behenolic acid into ketobrassidic acid (B. 26, 1867), whose oximes are then converted by the sulphuric acid into C8H17CO.NH[CHa]8CO,H (p. 300). (Oxidation, confp. Erucic and Brassidic Acids, p. 301.) DIOLEFINE CARBOXYLIC ACIDS 305 D. DIOLEFINE CARBOXYLIC ACIDS AV-Diolefine carboxylic acids are obtained by the two following general methods : — (1 ) By the condensation of aj8-olefine aldehydes with malonic acid, by means of pyridine (B. 35, 1143). C6H5N CH2:CH.CHO+CH2(COOH)a > CHa:CH.CH:CHCOOH+HaO+COa. (2) By the condensation of olefine aldehydes or ketones by means of halogen fatty acid esters and zinc, and subsequently splitting off water from the jS-hydroxy- olefine carboxylic esters thus formed, by heating with alkalis (B. 35, 3633 ; 36, 15, C. 1903, II. 555) : CH8CH:CH.CHO-fBrZnCHaCOaR > CH3CH:CH.CH(OH)CH3COOR > CH3CH:CH.CH:CH.COOH. Some of these acids are polymerized by barium hydroxide to di- and tri- molecular modifications which give up CO2, forming the corresponding cyclic or trimolecular hydrocarbons (B. 35, 2129) containing an eight-membered ring ; e.g. from j3- vinyl acrylic acid : CH4.CH:CH.CH, I =Cyclo-octadiene CHa.CH:CH.CH, CHj.CHiCH.CH, CH .CHiCH.CH =Dicyclo-dodecatricne AT CH2.CH: CH.CHj. Butadiene Carboxylic Acid, CH2:CH.CH:CHCO2H, m.p. 102°, is formed, together with ethylidene propionic acid (p. 298), by the reduction of Perchloro- butadiene Carboxylic Acid,CClz:CCl.CCl:CCLCO2H, m.p. 97°, and Perchlorobutine Carboxylic Acid, CC13.C:C.CC12.CO2H, m.p. 127°. These are products of decom- position resulting from the two hexachloro-R-pentenes (Vol. II.) on treatment with alkali (B. 28, 1644). product with water. Reduction by sodium amalgam brings at the 1,4 bonds (p. 90), forming a/?y-pentenic acid (p. 298). Oxidation with permanganate converts it into racemic acid (B. 35, 1136). It is isomeric with butadiene carboxylic acid, towards which it may stand in the same relation as fumaric acid to maleic acid (private information from Herr Doebner). Sorbic Acid, CHSCH=CH.CH=CH.COOH, m.p. 134-5°, b.p.228°,is obtained, together with malic acid, from the oil in the unripe juice of the berries of mountain ash (Sorbus aucuparia) (1859, A. W. Hofmann, A. 110, 129). It exists there in the form of a lactone, the so-called parasorbic acid (q.v.), which is boiled with sodium hydroxide or hydrochloric acid (B. 27, 351). Synthetically, it is prepared from croton aldehyde and malonic acid with pyridine (Doebner, B. 33, 2140), also from j3-hydroxy-y8-hexenic acid, by boiling it with a 20 per cent, barium hydroxide solution (B. 35, 3636). Oxidation by KMnO4 produces aldehyde and racemic acid (q.v.}, a reaction which reveals the structure of sorbic acid (B. 23, 2377; 24,85): CH8CH=CH.CH=CH.COOH+HaO+40=CH3CHO+COOH(CHOH)2COOH. Sorbic Acid. Racemic Acid. Sodium amalgam converts it into Hydrosorbic acid (p. 299). Heated with ammonia, sorbic ac^ yields a diaminocaproic acid ; hydroxylamine brings about a peculiar reaction resulting in acetyl acetone dioxime (p. 355) (B. 37, 3316). Sorbic Ethyl Ester, b.p. 95°, a-Methyl Sorbic Acid, m.p. 91°, a-Ethyl Sorbic Acid, b.p. 76°, and fib-Dimethyl Sorbic Acid, m.p. 93°, are obtained by method 2 (above). VOL. I. X 3o6 ORGANIC CHEMISTRY yc- Dimethyl SorbicAcid, b.p.M 165°. is prepared according to method i (p. 305) from a methyl fl-ethyl acrolein and malomc acid. Diallvl Acetic Acid, (CH2:CH.CHa)aCH.COaH, b.p. 227 , is obtained from ethyl-diallvl acetoacetate and diallyj [ malonic acid. Nitric acid oxidizes it to tricarballvlic acid (CO«H.CHj)jv^-HC/vJjri. Geranlc Acid belongs to the class of olefine dicarboxyhc acids. It will be described together with the olefine terpene bodies (Vol. II.). IV. DIHYDRIC ALCOHOLS OR GLYCOLS, AKD THEIR OXIDATION PRODUCTS The monohydric alcohols, with their oxidation products,— the alde- hydes, the ketones, and the monocarboxylic acids, with their deriva- tives,—were discussed in the preceding section. Closely allied to these are the dihydric alcohols or glycols, and such compounds as may be considered oxidation products of the glycols. The glycols are derived from the hydrocarbons by the replacement of two hydrogen atoms attached to two different carbon atoms by two hydroxyls. In the case of the monohydric alcohols we distinguished three classes — primary, secondary, and tertiary alcohols. With the glycols the classes are twice as numerous. The compounds, which may be considered as oxidation products of the glycols, contain either two similar, reactive, atomic groups — e.g. : the dialdehydes (glyoxal, CHO.CHO), the diketones (diacetyl, CH3CO.COCH3), the dicarboxylic acids (oxalic acid, COOH.COOH), and therefore exhibit double the typical properties of the oxidation products of the monohydric alcohols — compounds of double function / or they contain two different reactive atomic groups in the same molecule, and have, therefore, the typical properties of different families of compounds. The following bodies have such a mixed function : Aldehyde Alcohols (Glycolyl Aldehyde, CH2OH.CHO). Ketone Alcohols (Acetyl Carbinol, CH2OH.COCH3). Aldehyde Ketones (Pyroracemic Aldehyde, CH3.CO.CHO). Alcohol Acids or Hydroxyacids (Glycollic Acid, CH2.OH.COOH). Aldehydic Acids (Glyoxvlic Acid, CHO.CO2H). Ketonic Acids (Pyroracemic Acid, CH3.CO.COOH). Four classes — alcohols, aldehydes, ketones, and monocarboxylic acids — occur with the monohydric alcohols and their oxidation products, whilst in the case of the dihydric alcohols and their oxidation products ten classes of derivatives are known. The successive series in which these ten classes will be discussed readily follow, if their systematic interdependence be developed similarly to that of the univalent alcohols and their oxidation products. MONOHYDRIC ALCOHOLS AND THEIR OXIDATION PRODUCTS. I a. Primary Alcohols. 2. Aldehydes. 4. Monocarboxylic Acids, ib. Secondary Alcohols. 3. Ketones. lv. Tertiary Alcohols. DIHYDRIC ALCOHOLS OR GLYCOLS DIHYDRIC ALCOHOLS AND THEIR OXIDATION PRODUCTS. 307 la. Diprimary Glycols. 20. prim. Hydroxy- ya. prim. Hydroxycarboxylic CH2.OH CH2.OH Glycol. aldehydes. 4. Dialdehydes. CHO CH2OH Glycolyl Aldehyde. CHO CHO Glyoxal. 2b. sec. Hydroxyalde- hydes. 3a. prim. Hydroxyke-, tones. 5. Aldehydketones. •2C. tert. Hydroxyalde- hydes. 3&. sec. Hydroxyketones. 6. Diketones. $c. tert. Hydroxyketones. Acids. 8. Aldehydocarboxylic Acids. 10. Dicarboxylic Acids. COOH CHj.OH Glycollic Acid. CO,H COOH CHO COOH Glyoxylic Acid. Oxalic Acid. 76. sec. Hydroxycarboxylic Acids. 9. Ketone Carboxylic Acids. 'jc. tert. Hydroxycarboxy- lic Acids. i b. Prim. sec. Glycols. ic. Prim. tert. Glycols. i d. Disec. Glycols. le. Sec. tert. Glycols. i/. Ditert. Glycols. The dihydric alcohols and their oxidation products will be described and discussed in the following order : 1. Glycols, Dihydric Alcohols. 2. Hydroxy aldehydes, Aldehyde Alcohols. 3. Hydroxyketones, Ketone Alcohols. 4. Dialdehydes. 5. Aldehyde Ketones. 6. Diketones. 7. Hydroxy acids, Alcohol Monocarboxylic Acids. S. Aldehyde Monocarboxylic Acids. 9. Kefo-monocarboxylic Acids. 10. Dicarboxylic Acids. From the very nature of the conditions there are no compounds in any of these series which contain but one carbon atom in the mole- cule. However, carbonic acid with its exceedingly numerous derivatives will be introduced before the dicarboxylic acids — the carbonic acid group. Carbonic acid is the simplest dibasic acid ; it is similar, in many respects, to the dicarboxylic acids and a special type for such acids, which, like it, only occur in an anhydride form. Formic acid, the simplest acid, showing, at one and the same time, the character of an aldehyde and a monocarboxylic acid, might, for the very same reason, have been placed before glyoxylic acid, at the head of the aldehyde acids. However, it is customary to place formic acid at the head of the fatty acids, because the acid nature in it appears more prominently than does its aldehyde character. I. DIHYDRIC ALCOHOLS OR GLYCOLS A. PARAFFIN GLYCOLS Wurtz (1856) discovered glycol, and thus succeeded in filling the ap between the monohydric alcohols and the triacid alcohol, glycerol. chose the name glycol to indicate the relation of the new body to 3o8 ORGANIC CHEMISTRY alcohol on the one hand and glycerol on the other. Glycols are dis- tinguished as a-, 0-, y-, S-, etc., according as the hydroxyls are attached to adjacent carbon atoms (1,2), or in 1,3-, 1,4-, and 1,5- positions respectively. There are also diprimary, primary-secondary, etc., glycols (consult p. 307). The Geneva names are obtained for the glycols by attaching the final syllable " diol " to the name of the parent hydrocarbon. Glycols differ from the monohydric alcohols just as the hydroxides of bivalent metals differ from those of univalent metals, or as a dibasic acid from a monobasic acid. As a rule, the reactions leading from the monohydric alcohols and glycols to their corresponding derivatives are very similar. It is only in the case of the two hydroxyl groups of the glycols that they are able to pass successively to completion, and in so doing they give* rise first to substances which still show the character of a monohydric alcohol. Take ethylene glycol, for example : it is capable of forming a mono- and dialkali glycollate, corresponding with the alcoholates of the monohydric alcohols, mono- and dialkyl ethers, mono- and dihalogen esters, nitric acid esters and esters of organic acids, e.g. : CH..OH CH,.ONa CHa.ONa CH2.O.C2H8 CHa.O.CaHs I I I I ! CH2.OH CH2.OH CH2.ONa CH2.OH CH2.O.C2HS Glycol. Monosodium D,isodium Glycol Mono-ethyl Glycol Diethyl Glycollate. Glycollate. Ether. Ether. CH2.C1 CH2C1 CHj.O.COCH, CHa.O.COCH, CH2.OH CH2C1 CH2.OH CH2.O.COCHt Glycol Ethylene Glycol Monacetate. Glycol Diacetate. Chlorhydrin. Chloride. All the mono compounds also exhibit the character of monohydric alcohols ; they and the di- compounds, which have been mentioned, can be obtained from the glycols by the same methods as the corre- sponding transposition products of the monohydric alcohols. The sulphur- and nitrogen-containing derivatives of the glycols correspond with like derivatives of the monohydric alcohols : CHa.SH CHa.SH CHa.NHa CHa.NH, CH2.OH CHa.SH CH2.OH CHa.NH, Monothio-glycol.' Dithio-glycol. Hydroxyethylamine. Ethylene Diaraine- The aldehydes have been repeatedly spoken of as the anhydrides of dihydric alcohols, in which the two hydroxyl groups are joined to the same carbon atom, and which can only exist under special conditions. Yet, the ethers or acetals, esters and other derivatives of these hypo- thetical compounds are stable. These bodies are naturally isomeric with the corresponding derivatives of the dihydric alcohols, in which the hydroxyls are attached to different carbon atoms. The following, for example, are isomeric : — CH8.CH<g;g*g« Acetal and 9H*-aC*H» Glycol Diethyl Ether 2 6 CH-O^CH C\ C^C\C*~U f^T-T (~*\ f*f)r^TT CH 3. CH "\OCOCH 3 Ethylidene Diacetate and • 2' 3 Glycol Diacetate ' CH.O.COCri Aldehyde Ammonia and • 2 Hydroxyethylamine. DIHYDRIC ALCOHOLS OR GLYCOLS 309 The cyclic derivatives of the glycols are extremely characteristic. Thus, glycol yields two cyclic ethers : CH2V CH2.O.CH2 >O Ethylene Oxide. Diethylene Oxide, CH/ CH2.O.CH2 and also sulphur- and nitrogen-compounds corresponding with diethy- lene oxide : CH2V CH2.NH.CH, CH2.S.CH, CH2.NH.CHa 1 VH || || |i CH/ CH2.NH.CH2 CH2.S.CHa CH2.O.CH2 Ethylene Imide. Diethylene Imide. Diethylene Disulphide. Diethylene Imide Oxide. Methods of Formation. — The first three methods are concerned with the olefines, and lead, according to the constitution of the latter, to glycols of every description. The halogen addition products of the olefines — the alkylene halides — may be regarded as the halogen acid esters of the glycols. When these are acted on by alkalis, with the purpose of exchanging hydroxyl for their halogen, by loss of halogen acid, they pass first into monohalogen olefines and then into acetylenes. It was Wiirtz who observed that it was only necessary to treat the alkylene halides with acetates in order to reach the acetic esters of the glycols, and then, by saponification with alkalis, to obtain the glycols. (i) By heating the alkylene halides (p. 94) with silver acetate and glacial acetic acid, or with potassium acetate in alcoholic solution : CH2I CH3COOAg CH2OCOCH3 CH2I+CH3COOAg = CH2OCOCH3 Ethylene Diacetate. Inasmuch as the alkylenes are prepared from monohydric alcohols by withdrawal of water, and are transformed by the addition of halogens into alkylene halides, the preceding reaction may be regarded as a method of converting monohydric alcohols into dihydric alcohols or glycols. The resulting acetic esters are purified by distillation, and then saponified by KOH or barium hydroxide solution (C. 1899, 1. 968) : CHaOCOCH3 KOH CHaOH + = | +2CH3COOK. CHaOCOCH3 KOH CH2OH A direct conversion of alkylene halides into glycols may be attained by heating them with water (A. 186, 293 ), with water and lead oxide, or sodium and potassium carbonates. (2) Another procedure consists in shaking the alkylenes, CnH2n, with aqueous hypochlorous acid, and afterwards decomposing the chlorhydrins fdrmed with moist silver oxide : CHj OH CH2OH AgOH CHjOH CH, Cl ~CH2C1 CH2OH (3) By the oxidation of the olefines (a) in alkaline solution (p. 84) (Wagner, B. 21, 1230) with potassium permanganate, or (b) with hydrogen peroxide. Thus, ethylene yields ethylene glycol; isobutylene, isobutylene glycol, (CH8)a.C(OH').« CHa.OH : CHa CH2.OH || +0+H.O = | CHg CHa.OH 3IO ORGANIC CHEMISTRY (4) By the action of nitrous acid on diamines (p. 163). As they can be obtained from the corresponding nitriles of dibasic acids, and the nitriles themselves from alkylene halides, these reactions not only ally the classes of derivatives mentioned, but they afford a means of building up the glycols : CH2Br CHaCN CHaCHaNHa CH2CH2OH CH2 ^CH2 ^CH2 ^CH2 CH2Br CH2CN CH2CH2NH2 CH2CH2OH Trimethylene Trimethylene Pentamethylene Pentamethylene Bromide. Cyanide. Diamine. Glycol. Besides the normal glycols, isomeric glycols are sometimes obtained, as well as olefine alcohols and diolefines (B. 40, 2589). (50) By reduction of aldehydes or keto-alcohols, dialdehydes or dike tones. By this means the a-keto-alcohols butyroin and caproin (p. 342) yield the stereoisomeric forms of 4,5-octane-diol and 6,7-decanedo- diol ; aldol (p. 338) gives ay-butylene glycol ; y-acetobutyl alcohol (p. 342) gives i,5-hexane-diol, and acetonyl acetone (p. 351) yields 2,5-hexane-diol. Akin to these reactions is the formation of glycol by the conden- sation of isobutyl alcohol, alone or when mixed with other aldehydes, by means of alcoholic potassium hydroxide. An aldol (p. 338) is first formed, of which the aldehydic group is acted on by excess of butyl aldehyde producing a monobutyrin of the i,3-glycol (comp. p. 194), which in turn is decomposed by hydrolysis into the glycol and iso- butyric acid (M. 17, 68 ; 19, 16) : 3(CH3)aCH.CHO > (CH3)2CH.CH(OH) CH(CH3)2 (CH3)aCH.CHOH (CH3)aC.CH2O CO (CH8)2C.CHaOH CH(CH3)2 COOH. (5&) By the reduction of dicarboxylic esters or amides by sodium and alcohol (C. 1905, II. 1701). (CH3)2C.CO2R (CH3)2C.CH2OH CH2.COaR CH2CH2OH unsym.-Dimethyl ^-Dimethyl Tetramethylene Succinic Ester. Glycol. CHa.CHa.CH2.CONH2 CH2.CHa.CHaCH2OH CHa.CHa.CH2.CONHa CH2.CH2.CH2CH2OH. Suberic Amide^ Octomethylene Glycol. Lactones, the cyclic esters of y-, 8-, or €-hydroxy-carboxylic esters, are also reduced to glycols by sodium and alcohol (B. 39, 2851); similarly, j8-ethoxyl propionic ester yields the ethyl ether of trimethyl- ene glycol (C. 1905, I. 25). Nucleus Synthetic Methods (6a) Aldehyde alcohols, diketones, keto-carboxylic esters, dicar- boxylic esters, all react with alkyl magnesium halides (p. 185) forming :H2COOC2H6 CH2C(CH8)2OH lethyl Tetramethylene Glycol. DtHYDRIC ALCOHOLS OR GLYCOLS 311 glycols, accompanied by the entry of an alkyl group (B. 35, 2138 ; C. 1904, I. 578 ; 1906, II. 1639 ; I907> L 627) : CH,CH(OH) CH,Mgl CH8.CH(OH) CHjCHO CH2CH(OH)CH8 Aldol. Dimethyl Trimethylene Glycol. CH2COOCaH6 4CH3Mgl CH2C(CH3)2OH C Succinic Ester. Tetramethyl By the same reagent alkoxy-ketones and alkoxy-carboxylic esters are converted into monoalkyl ethers of the glycols (C. 1904, I. 504). Similarly, lactones yield primary-tertiary glycols (C. 1907, I. 708). (6b) The action of metals, such as sodium or magnesium, on many halogen-hydrin compounds of the ethers, either alone or mixed with halogen methyl alkyl ethers (p. 206), is to build up the ethers of the higher glycols from lower members (C. 1903, I. 455 ; 1904, 1. 1401) : Na 2C8H5O.CH2CH,CH,I - > C6H60[CH2]SOC6H6 - > HO[CH2]6OH y-Phenoxypropyl Iodide. Hexamethylene Glycol. HO[CH2]4OH rameth Glycol. The monoalkyl ethers of the glycols can be obtained by the similar reaction of chloromethyl alkyl ether on ketones in the presence of magnesium or other metals (C. 1907, I. 681). (7) Ditertiary glycols result, together with secondary alcohols, in the reduction of ketones (p. 230). In this manner pinacone or tetra- methyl ethylene glycol (p. 313) was made from acetone (Ffiedel) : Amyloxypropyl Tetramethylene Bromide. (8) A few glycols have been obtained in the form of their dialkyl ethers by the electrolysis of alkoxy-carboxylic acids. This is similar to the production of ethane from potassium acetate (p. 73, and C. 1905, I. 1698). Properties. — The glycols are neutral, thick liquids, holding, as far as their properties are concerned, a place intermediate between the monohydric alcohols and trihydric glycerol. The solubility of a compound in water increases according to the accumulation of OH groups in it, and becomes correspondingly less soluble in alcohol, and especially in ether. There will be also an appreciable rise^in the boiling point, whilst the body acquires at the same time a sweet taste, inasmuch as there occurs a gradual transition from the hydro- carbons to the sugars. In accord with this, the glycols have a sweetish taste, are very easily soluble in water, slightly soluble in ether, and boil much higher (about 100°) than the corresponding monohydric alcohols. As the number and dimensions of the alkyl groups grow, the higher homologues become increasingly soluble in ether, and the taste becomes sharper and, in some cases, burning. Behaviour. — (i) Towards dehydrating agents : (a) The 1,2- glycols, when heated with zinc chloride, P2O5, dilute acids or even water at 3i2 ORGANIC CHEMISTRY high temperatures, are converted into aldehydes or ketones, e.g. CH3CH(OH)CH2OH - ^CH3.CH2.CHO and CH3COCH3 (see also the transformations of the glycols and changes of the pinacones pp. 216, 313). (b) The 1,4- and i,5-glycols yield cyclic oxides (p. 316). (c) The i,3-glycols form cyclic oxides and also aldehydes and ketones (M. 23, 60). (2) Many glycols, especially the primary, when oxidized, pass into the corresponding oxidation products (see Ethylene Glycol) ; others break down with fracture of the carbon chains. (3) On the reactions with halogen acids, nitric acid, concentrated sulphuric acid, acid chlorides, and acid anhydrides, see esters of the glycols (p. 319). I. Ethylene Glycol, Glycol, [i,2-Ethane diol], CH2OH.CH2OH, m.p. —11*5°, b.p. I97'5°, DO = 1*125, is rniscible with water and alcohol. Ether dissolves but small quantities of it. It may be obtained from ethylene through ethylene bromide, ethyl- ene chlorhydrin (general method of formation, p. 309) or by direct oxidation ; and also from ethylene oxide by the absorption of water : CH» CH2.OH Preparation. — A mixture of ethylene bromide, potassium carbonate and water is boiled under a reflex condenser, until all the bromide is dissolved (A. 192, 240, 250). Or the «thylene bromide may be converted by heating with anhydrous potassium acetate into glycol diacetate, which yields glycol when hydrolyzed with alkali hydroxide (B. 29, R. 287 ; C. 8991, I. 968). Behaviour. — (i) On heating ethylene gtycol with zinc chloride to 250° water is eliminated and acetaldehyde and crotonaldehyde are formed ; at 210° with water, only acetaldehyde results. When ethylene glycol is distilled with 4 per cent, concentrated sulphuric acid, not only acetaldehyde and ethylidene ethylene ether (p. 317) are formed, but also Diethylene Oxide. Further treatment with sulphuric acid or zinc chloride results similarly in the production of acetaldehyde : CHa— O— CHa CH..O— CH8 CH3 HOCH, ,OH CH,— O— CH, CH— O— CH, CHO HOCH2 (2) Nitric acid oxidizes glycol to gly collie acid and glyoxal, glyoxylic acid and oxalic acid. The first oxidation product, glycol aldehyde (q.v.), is further oxidized too rapidly to be identified : CH2.OH COOH CHO COOH COOH CH..OH CH2OH CHO"" ^CHO *" COOH Glycol. Glycollic Acid.' Glyoxal: Glyoxylic Acid. Oxalic Acid: ^ (3) When glycol is heated with potassium hydroxide to 250°, it is oxidized to oxalic acid with evolution of hydrogen. (4) Heated to 160° with concentrated hydrochloric acid, glycol chlorhydnn results, which at 200° is converted into ethylene chloride. (5) The latter is also produced when PC16 acts on glycol. CH £ DIHYDRIC ALCOHOLS OR GLYCOLS 313 (6) A mixture of nitric and sulphuric acids changes gtycol into glycol dinitraU. (7) Concentrated sulphuric acid and glycol yield glycol sulphate. (8) The acid chlorides or acid anhydrides produce mono- and di- esters of glycol. Glycollates : Metallic sodium dissolves in glycol, forming sodium glycollate, C2H4<C;;-,ST , and (at 170°) disodium glycollate, C2H4(ONa)a. Both are white, crystalline substances, regenerating glycol with water. The alkylogens convert them into the corre- sponding ethers. Polyethylene Glycols : Ethylene oxide absorbs water and becomes glycol. The latter and ethylene oxide unite at 100° in varying proportions, thus yielding the polyethylene glycols : CH2V CH2OH /CH2CH2OH >O+ 1 =O< Diethylene Glycol, b.p. 250°. H/ CH2OH XCH2CH2OH CH2OH CH2— O— CH2CH2OH Triethylene Glycol, b.p. 287°. CH2OH CH2— O— CH2CH2OH etc. The polyglycols are thick liquids, with high boiling points. They behave like the glycols. Ether-acids may be obtained from them by oxidation with dilute nitric acid ; thus diglycollic acid (q.v.) is formed from diethylene alcohol. There are two series of homologues of ethylene glycoi ; the one resulting from alkyl substitution, and the other, including the 1,3-, i,4-,i,5-glycols, etc., produced by the insertion of an alkyl group between the carbinol groups. II. Homologous i,2-glycols. a-Propylene Glycol, Methyl Ethylene Glycol [Propane diol-i,2], CH3.CH(OH).CH2.OH, b.p. 188°, D0=roi5, is obtained from pro- pylene bromide or chloride. It is most readily prepared by distilling glycerol with sodium hydroxide (B. 13, 1805). Platinum black oxidizes it to ordinary lactic acid. Only acetic acid is formed when chromic acid is the oxidizing agent. Concentrated hydriodic acid changes it to isopropyl alcohol and its iodide. Heated with water at about 190° it yields propylaldehyde and acetone. It contains an asymmetric carbon atom, and when exposed to the action of the ferment Bacterium lermo, becomes optically active (B. 14, 843). a-Butylene Glycol, Ethyl Ethylene Glycol, C2H6CH(OH).-\ CH2OH, b.p. 192°. Py-Butylene Glycol, sym.-Dimethyl Ethylene Glycol, Are obtained f rom the CH3CH(OH).CH(OH).CH3, b.p. 184°. / corresponding butyl- Isobutylene Glycol, unsym.-Dimethyl Ethylene Glycol, ene bromides- (CH3)2C(OH).CH2(OH), b.p. 177°. ; a-Isoamylene Glycol, Isopropyl Ethylene Glycol,\ «^ G/y Are obtained ,0-n the (CH3)2C(OH).CH(OH)CH3, b.p. 177°. ( corresponding amyl, fA mylene Glycol, sym.-Ethyl Methyl Ethylene Glycol, ene d C2H6CH(OH)CH(OH).CHa, b.p. 187°. Pinacone, Telramethyl Ethylene Glycol, (CH3)2.C(OH).C(OH).(CH8)2+6HtO, m.p. 42°, anhydrous, m.p. 38°, b.p. 171-172°, is formed, together with isopropyl alcohol, when sodium or magnesium and mercuric chloride (C. 1906, II. 148) 3i4 ORGANIC CHEMISTRY act on acetone ; or by electrolysis (B. 27, 454 '> c- I9°°. H. 794) (see method of formation, No. 8, p. 311). Further, by the action of IMgCH8 on diacetyl or oxalic ester (mode of formation, No. 6a). It crystallizes from its aqueous solution in quadratic plates (hence the name, from 7nVa£, plate), and gradually effloresces on exposure. In common with other ketones (p. 216), dilute sulphuric or hydrochloric acids cause it to lose water and undergo intramolecular change, forming pinacoline or tert.-butyl methyl ketone (p. 224). An isomer of this substance exists — tetramethyl ethylene oxide (p. 318), which very readily absorbs water forming pinacone. Similarly to pinacone, a whole series of tetra-alkylated ethylene glycols can be prepared by reduction of aliphatic ketones, known collectively as Pinacones, which behave towards dilute sulphuric and hydrochloric acids as pinacone itself does. Comp. Methyl Isopropyl Pinacone, C. 1903, II. 23. sym.-Dipropyl Ethylene Glycol [Octane diol-4,5], C3H7CH(OH).CH(OH)C3H7, occurs in two modifications ; a-form, liquid, b.p.10 115-120°, /?-form, m.p. 125°, and is prepared by reduction of butyroin (p. 342) by sodium and alcohol. ssym.-Dipentyl-ethylene Glyeol [Dodecane diol-6,7], a-form, m.p. 54°, b.p.10 155-160° ; j8-form, m.p. 136°, is produced when capronom is reduced by sodium and alcohol (C. 1906, II. 1114); III. i,3-Glycols. Trimethylene Glycol [Propane diol-i.s], CH,OH.CH2CH2OH, b.p. 216°, D.0= i '065, is obtained from trimethylene bromide (B. 16, 393) ; or by the fermenta- tion of glycerol by Schizomycetes, together with w-butyl alcohol (B. 20, R. 706). It is isomeric with a-propylene glycol. Moderate oxidizing agents produce fl-Hydroxypropionic Acid or Hydr acrylic Acid; sulphuric acid changes it intopro- pionaldehyde and acetone (C. 1904, I. 1401). fi-Butylene Glycol, fi-M ethyl Trimethylene Glycol [Butane diol- 1,3] CH3CH(OH)- CH2OH, b.p. 207°, is obtained by the reduction of aldol (p. 338) ; 50 per cent, sulphuric acid converts it into butyl aldehyde and methyl ethyl ketone (comp. p. 312, and C. 1904, I. 1400). y-Isoamylene Glycol, aa-Dimethyl Trimethylene Glycol, (CH3)aC(OH).CH2CH2- OH, b.p. 203°, is obtained from the bromide (B. 29, R. 92). sym.-Dimethyl Trimethylene Glycol [Pentane diol-2,4], CH3CH(OH)CH2CH- (OH)CH3, b.p. 199°, is prepared by reduction of hydracetyl acetone (p. 342) ; and by the action of magnesium methyl iodide on aldol (C. 1904, 1. 1327 ; B. 37, 4730). aay-Trimethyl Trimethylene Glycol, 2,4-Isohexylene Glycol, (CH3)2C(OH)CH2- CHaCH(OH)CH3, b.p. 194°, is obtained by reduction of diacetone alcohol (p. 342). sym.-Tetramethyl Trimethylene Glycol, (CH3)2C(OH).CH2.C(OH)(CH3)2, b.p.13 98°, results from the action of CH3MgI on diacetone alcohol (C. 1902, I. 455 ; B. 37, 473 1). A series of higher homologues of the i,3-glycols is obtained from the con- densation of isobutyl aldehyde with other aldehydes, such as the isobutyl aldols, by means of alcoholic potassium hydroxide (method of formation No. 50, p. 310). ^-Dimethyl Trimethylene Glyeol, Pentaglycol, (CH3)2C(CH2OH)2, m.p. 129°, b.p. 206°. Heated with H2SO4 it forms isovaleric aldehyde, isopropylmethyl ketone and a cyclic oxide (C. 1900, II. 36). aBB-Trimethyl Trimethylene Glycol, CH2(OH)C(CH8)2CH(OH)CH8, b.p. 207°, and a^-Ethyl Dimethyl Trimethylene Glycol, m.p. 81°, are obtained from isobutyl aldehyde, and acetaldehyde and propionaldehyde, respectively. aBB-Isopropyl Dimethyl Trimethylene Glycol, CH2(OH)C(CH8)2CH(OH)C3H7, m.p. 51°, b.p. 223°, is prepared from isobutyl aldehyde alone. This substance on oxidation yields first a hydroxy-acid and then diisopropyl ketone. sym.'Tetramethyl p-Ethyl Trimethylene Glycol, (CH3)2C(OH)CH(C2H6)C(OH)- (CH,)2, b.p.n 128°, is obtained from ethyl acetoacetic ester and CH3MgI (mode of formation 6a, p. 310) (C. 1902, I. 1197). IV. i,4-Glycols. Tetramethylene Glycol, [Butane diol-i,4], HO.CH2.CHa.CH2CH2OH, b.p. 202-203°, D = i-oi i, is prepared from tetramethylene dinitramine and sulphuric acid (B. 23, R. 506) ; also, by reduction of succinic dialdehyde (p. 347), by aluminium amalgam. It possesses an unpleasant odour of leeks (B. 35, 1187). UNSATURATED GLYCOLS, OLEFINE GLYCOLS 315 The Diamyl Ether results from the electrolysis of the potassium salt of j8-amyloxy- propionic acid (C. 1901, I. 613 ; 1905, I. 1698). a-Methyl Tetramethylene Glycol, (Pentane diol-i,4), CH3.CH(OH)CH2CH2CH2- OH, b.p.J6 123-126°, with partial decomposition into y-pentylene oxide and water. It is obtained from acetopropyl alcohol (C. 1903, II. 531) and from yvalerolactone by reduction (B. 39, 2851). a-Dimethyl Tetramethylene Glycol, i.^-Isohexylene Glycol, (CH3)2C(OH)CH2- CH2CHaOH, b.p. 222°, results from the action of CH3MgI on butyrolactone (C. 1907, I. 708). p-Dimethyl Tetramethylene Glycol, CH2(OH)C(CH3)2CH2CH2OH, b.p.10 123°, is produced from unsym.-dimethyl succinic ester by reduction with sodium and alcohol (1905, II. 178). ao-Dimethyl Tetramethylene Glycol, 2,$-Hexylene Glycol, [Hexane diol-2,5] CH3CH(OH)CH2CH2CH(OH)CHa> b.p. 217°, is easily obtained by the reduction of acetonyl acetone by sodium amalgam (B. 35, 1335). V. i,5-Glycols. Pentamethylene Glycol, [Pentane diol-i.s], HOCH2.CH2.CH2CH2CH2OH, b.p. 239°, Dlg=o'994, is obtained frompentamethylene diamine (mode of formation 4, p. 310) (B. 40, 2559). Diamyl Ether is prepared from S-amyloxybutyl bromide, magnesium and bromomethyl amyl ether (mode of formation 6b., p. 311 ) (C. 1904, 11.587). a-Methyl Pentamethylene Glycol, [Hexane diol-i,5], CH3CH(OH)[CH2]8CHaOH, b.p.710 235°, is produced from acetobutyl alcohol (p. 342). VI. 1,6-, 1,7-, i,8-Glycols, etc. The melting points of these polymethylene glycols appear to follow the same rule as those of the normal paraffin mono- and di-carboxylic acids and other homologous series (p. 48), namely, that those of members possessing an odd number of atoms lie lower than those of the neighbouring even-numbered members (C. 1904, II. 1698). Hexamethylene Glycol, [Hexane diol-i,6], HO[CH2]6OH, m.p. 42°, b.p. 250°, is prepared from hexamethylene dibromide or diacetate ; and from adipic ester by reduction. Dialkyl Ether is obtained from y-alkoxypropyl halides by the action of sodium (methods of formation 6b and 8 (p. 311); and from y-amyloxybutyric acid by electrolysis (B. 27, R. 735 ; C. 1905, I. 1698 ; II. 1701). Heptamethylene Glycol, Diethyl Ether, C2H6O.[CH2]7OC2H5, b.p. 225°, results from the interaction of 6-ethoxyhexyl iodide, magnesium and iodomethyl ethyl ether (mode of formation 6b, p. 311) (C. 1906, I. 4.43). Octomethylene Glycol, [Octane diol-i,8], HO[CH2]8OH, m.p. 60°, b.p.0 162°. Enneamethylene Glycol, [Nonane diol-1,9], HO[CH2]9OH, m.p. 45°, b.p.1B 177°. Decamethylene Glycol, [Decane diol-i.io], HO[CH2]10OH, m.p. 70°, b.p.15 179°. These glycols are obtained from dicarboxylic esters or amides by reduction (mode of formation 56, p. 310) (C. 1904, I. 1399 ; 1905, II. 1701). B. UNSATURATED GLYCOLS, OLEFINE GLYCOLS, ACETYLENE GLYCOLS Unsaturated dihydric alcohols have been but slightly investigated. The simplest representatives possible theoretically are not known, and probably are not capable of existing. See p. 318, upon the view of furfurane as an oxide of an unknown, unsaturated glycol. Also consult acetonyl acetone (p. 351). iso-Dipropionyl, iso-dibutyryl, iso-diisobutyryl, and iso-diisovaleryl are olefine glycol derivatives. They resulted from the action of metallic sodium on an ethereal solution of propionyl chloride, butyryl chloride, and isobutyryl chloride, and iso-valeryl chloride. They are esters of alkyl acetylene glycols (Klinger and Schmitz, B. 24, 1271 ; B. 28, R. 1000 ; J. pr. Ch., [2], 63, 364). CnHK.C.OCOCaH,; Diethyl Acetylene Glycol Dipropionate, Dipropionyl, * - .__ _ V_ , b.p.10 o H /2 g.'.v-o 5 CHC OCO C H 108°. Di-n-propyl Acetylene Glycol Dibutyrate, Dibutyryl, '7 ' 8T 3I6 ORGANIC CHEMISTRY b.p-12 119-130°- Diisobutyl Acetylene Glycol Diisovalerate, Diisovaleryl, (CH3)2.CH.CH2.C— OCOC4H9 145-155°. Butyroin and isovaleroin, the (CH8)2.CH.CH2.C-O.COC4H9' corresponding a-ketone alcohols (q.v.), are produced, and not the alkyl acetylene glycols, when these three compounds are saponified. The diacetate, CH3C- (OCOCHj) : C(OCOCH8)?CH8, is produced from the di-sodium salt of acetoin (p. 341) and acetyl chloride. Hexa-di-ine dial, CH2(OH)C :C-C:C.CHa.OH, m.p. 111°, is a diacetylene glycol. It is formed by the oxidation of the precipitate from propargyl alcohol and ammoniacal cupric chloride with potassium ferricyanide (C. 1897, 1, 281 ; II. 183). GLYCOL DERIVATIVES I. ALCOHOL ETHERS OF THE GLYCOLS A. The alcohol ethers of the glycols are prepared (i ) from the metallic glycolates and alkyl iodide : CH2ONa ^ I=N^ CH2OC2H6 Qlycol Monoeihyl Eihey> b p I2?o (B 35> CHaOH CH2OH CH2ONa CaH6I CH2OCaH5 + =2NaI + 1 Glycol Diethyl Ether, b.p. 123°. CH2ONa C2H6I CH,OC2H6 (2) The monoalkyl ethers of ethylene glycol result from the combination of ethylene oxide and alcohol. (3) Dialkyl ethers can be obtained synthetically by means of the methods of formation 6b and 8 (p. 311) : (a) From halogen-substituted ethers RO[CH2]n X and Na or Mg ; (b) From ketones with chloromethyl alkyl ethers and magnesium ; (c) From alkoxy ketones and alkoxycarboxylic esters with magnesium alkyl halides. (d) From alkoxy fatty acid salts by electrolysis. Hydriodic acid de- composes the neutral ethers into iodoalkyls and glycols (B. 26, R. 719), which are converted into alkylene iodides by excess of HI. Hydrobromic acid in the cold converts glycol dialkyl ether into the bromo- hydrins of the mono-alkyl ether, RO[CHa]nBr (C. 1904, 1. 1400). The mono-alkyl ethers of tertiary- primary i,2-glycols are changed into alde- hydes by the action of anhydrous formic or oxalic acid (comp. p. 192). The polyethylene alcohols are most closely related to the alcohol ethers. They have been already considered after ethylene glycol (p. 312). Diethylene glycol bears the same relation to glycol as ethyl ether to ethyl alcohol : Bne Glycol (First Ether of Glycol). B. Cyclic Ethers of the Glycols, Alkylen Oxides. Diethylene Oxide, O<£^2-£^a>O, m.p. 9°, b.p. 102°, is the second ether of glycol (see above, Diethylene Glycol). It is obtained from the red, crystalline bromine addition product of ethylene oxide, (CaH4O)2Bra, m.p. 65°, b.p. 95°, when it is treated with mercuric oxide. It is also prepared by heating glycol with con- :entrated sulphuric acid (p. 312). It unites with bromine, forming the above- mentioned dibromide ; with iodine, to a diiodide, m.p. 85° ; and with sulphuric acid it forms a sulphate, m.p. 101°. Thus, it forms double compounds or oxonium salts similar to those of the simple ethers (p. 126) (C. 1907, I. 1103). It is de- composed into acetaldehyde and glycol when heated with sulphuric acid (p. 312). Ethylene Methylene Ether, Glycol Methylene Acetal, ^H2'°>CH2, b.p. 78°, is obtained from trioxymethylene. ethylene glycol and ferric chloride (B. 28, R. 109). GLYCOL DERIVATIVES 317 or syrupy phosphoric acid (C. 1899, I. 919). Also from glycol, formaldehyde and hydrochloric acid (C. 1900, II. 1261). Ethylene Ethylidene Ether, CH2 Q>CH.CH3, b.p. 82'5°, results from the union of ethylene oxide and acet- aldehyde (comp. p. 312). Diethylene oxide is a cyclic double ether. For the preparation of this class of substance the i,3-glycols seem also to be suitable (M. 23, 67). Simple cyclic ethers or glycol oxides are also known ; and a third ether, Ethylene Oxide, c^*-^0 (w^rtz)> is also derived from glycol. The simple cyclic ethers of the glycols, the alkylene oxides, are readily pro- duced in various ways, depending upon whether the two OH-groups are attached to adjacent carbon atoms or not. Alkylene oxides, in which the O-atoms are in union with adjacent carbon atoms, are termed the a-alkylene oxides, whilst the others are the /?-, y-, S-alkylene oxides. (i) Ethylene oxide itself and the ethylene oxides, as well as the /3-alkylene oxides (trimethylene oxide), are pre- pared by the action of potassium hydroxide on the chlor- or brom-hydrins, the monohaloid esters of the respective glycols : (2) The y- and 8-alkylene oxides (y-pentylene oxide, pentamelhylene oxide), are formed when the glycols are heated with sulphuric acid (B. 18, 3285 ; 19, 2843 ; M. 23, 67) : /CH2.CH2OH H2S04 /CH2.CH3V CH/ - —>CH/ >0+H20. XCHa.CH2OH NCHa.CH/ The a-glycols, under like treatment, lose water and yield either un- saturated alcohols, aldehydes, or pinacolines, depending upon their constitution (pp. 192, 216, 312). The ethylene oxide ring is easily ruptured, hence ethylene oxide enters into addition reactions quite as freely as its isomer acetaldehyde. The rings of tetra- and pentamethylene oxides, however, are far more stable. These can only be broken up by the halogen acids. Ethylene Oxide, ?Ha>O, b.p. 12-5°, 0.0=0-898 ,isomeric with acet- CHa aldehyde, CH3.CHO, is a pleasantly smelling, ethereal, mobile liquid, with a neutral reaction, yet able gradually to precipitate metallic hydroxides from many metallic salts. CHa.OH OH =26H;a +Mg<OH Ethylene oxide is characterized by its additive power, (i) It combines with water and slowly yields glycol. (2) Nascent hydrogen converts it into ethyl alcohol. (3) The halogen acids unite with it to form halogenhydrins, the mono- haloid esters of the glycols ; hydrofluoric acid is, however, an exception (C. 1903, I. n). (4, a) With alcohol it yields glycol monoethyl ether ; (b) with glycol it forms diethylene glycol ; (c) and with the latter it combines to triethylene glycol. (5) It forms ethylene alkylidene ethers (p. 316) with aldehydes. (6) Acetic acid and ethylene oxide form glycol monacetate, and (7) with acetic anhy- dride the product is glycol diacetate. (8) Sodium bisulphite changes it to sodium isethionate. (9) Ammonia changes ethylene oxide to hydroxyethylamine. (10) With hydrocyanic acid it forms the nitrile of ethylene lactic acid or hydracrylic acid, from which hydrochloric acid produces the ethylene lactic acid itself. ( 1 1 ) Ethylene oxide unites with sodium malonic ester (see Hydroxethyl Malonic Ester). Potassium hydroxide polymerizes ethylene oxide at 50-60° (B. 28, R. 293). For comparison, the following additive reactions of ethylene oxide and alde- hyde are arranged side by side : ORGANIC CHEMISTRY KHS03 CH2.OH KHSO^ CH ^ l~ ^CH^SO.K NHs CH2.OH CH8.CH:0 CH2.NH, HNC CH..OH CN NH3 -> CH3, HNC ^iH, CH..CH- Ethylene oxide and magnesium alkyl halides form addition compounds, which are converted by heat into primary alcoholates, RCH2CHaOMgX (pp. 107, 185). Heated with a little potassium hydroxide at 50-60°, ethylene oxide polymerizes (B.28.R.S95). CH (CH a-Propylene Oxide, | >O, b.p. 35°. Isobutylene Oxide, \ ,O, CH.% CH3' b.p. 51-52°. sym.-Dimethyl Ethylene Oxide, b.p. 56-57°. sym.-Methyl Ethyl Ethylene Oxide, b.p. 80°. Isopropyl Ethylene Oxide, b.p. 82°. Trimethyl Ethylene Oxide, b.p. 75-76°. Tetramethyl Ethylene Oxide, b.p. 95-96°, is produced from tetramethyl ethylene bromide by PbO and water (C. 1902, I. 628). It unites with water to form pinacone with considerable evolution of heat (p. 313). Heated to 200-260° with A12O3 or other contact substances, ethylene oxide, propylene oxide and isobutylene oxide are transformed into the isomeric alde- hydes, acetaldehyde, propionaldehyde, isobutyl aldehyde, whilst trimethyl ethylene oxide gives methyl isopropyl ketone (B. 36, 2016). Trimethylene Oxide, CH,<£^2>O, - b.p. 50°; preparation, see p. 317; homologues (M. 23, 67 ; C. 1906, II. 1179). CH2(j9)-CH2(a) x Tetramethylene Oxide, Tetrahydrofurfurane, )O, b.p. 57° CH.O^-CHifo) / (B. 25, R. 912). 2,5-Hexylene Oxide, aa^Dimethyl Tetrahydrofurfurane, b.p. 93° (B. 35, 1336). aa-Dimethyl Tetramethylene Oxide, b.p. 98° (C. 1907, I. 708), Diisocrotonyl Oxide, aa^Tetramethy I Tetrahydrofurfurane, b.p. 113°. Diisoamylene Oxide, aa^Dimethyl-aa-Diethyl Tetrahydrofurfurane, b.p. 160° (C. 1899, 1. 774, 775). y-Pentylene Oxide, a-Methyl Tetrahydrofurfurane, b.p. 77° (p. 314) (B. 22, 2571). Pentamethylene Oxide, CH2<£^2~£^2>O, b.p. 82° (B. 27, R. 197). 8-Hexylene Oxide, a-Methyl Pentamethylene Oxide, b.p. 104°, does not unite with ammonia (B. 18, 3283). The higher polymethylene glycols are converted into their oxides with difficulty. Decamethylene Oxide, b.p. 181°, has, however, been prepared, by distilling the chlorohydrin of decamethylene glycol over sodium hydroxide (C. 1906, II. 596). Addendum. — Furfurane corresponds with tetramethyl ene oxide. It may be considered as the cyclic ether of an unknown, unsaturated glycol. It is probable that this glycol could not exist ; it would be more likely to become rearranged into succinic dialdehyde, and this in turn to y-butyrolactone (q.v.) : CH2.CH2OH CHa.CH2v CH=CHOH CH=CHV I I >0 | | >0 CH2.CH2OH CH2.CH/ CH=CHOH CH=CH/ Tetramethylene Tetramethylene Unknown. Furfurane. Glycol. Oxide. By the substitution of sulphur and again of the NH-group for oxygen in furfurane the products are thiofurfurane, which, from its remarkable resemblance to benzene, has been called Thiophene, and Pyrrol. Notwithstanding that the manner of union in the rings of these heterocyclic compounds is not definitely known, it is possible to refer many bodies to them : CH=CHX CH=CHV CH=CHV >0 | >S >NH CH=CH/ CH=CH/ CH=CH/ Furfurane. Thiophene. Pyrrole. GLYCOL DERIVATIVES 319 All of them contain rings, and they will be discussed later in conjunction with related classes of heterocyclic derivatives. 2. ESTERS OF THE DIHYDRIC ALCOHOLS OR GLYCOLS A. Esters of Inorganic Acids. (a) Halogen Esters of the Glycols. — The glycols and monobasic acids yield neutral and basic esters. The dihalogen substitution products of the paraffins are the neutral or secondary halogen esters of the glycols. The halogen atoms in them are attached to different carbon atoms. They are isomeric with the alde- hyde halides (p. 206) and the hetone halides (p. 225), having an equally large carbon content : CH2C1 CHoCl CHCL CH. II II CHC1 and CHa are isomeric with CH2 and CC1, CH3 CH2C1 CH3 CHS Propylene Trimethylene Propvlidene Chloracetol Chloride. Chloride. Chloride (p. 225). (p. 206). The basic or primary haloid esters of the glycols are the halohydrins. These are obtained : (1 ) When the glycols are treated with hydrochloric and hydrobromic acids : CH2OH CH2OH + HC1= | +H80. CH2OH CH2C1 When heated with HI, a more far-reaching reaction occurs. Ethyl iodide (p. 136) is obtained from ethylene glycol. The result of the action of HBr on neutral glycol ethers in the cold is the pro- duction of the ether of the bromhydrin. Like the ether of the chlorhydrin, it can also be obtained from the benzoyl derivative of the alkoxy-alkylamines by PC1B or PBr,, with the loss of benzonitrile (comp. p. 320) (B. 38, 960). (2) They can be obtained, too, by the direct addition of hypochlorous acid (see Inorg. Chem.) to the olefines, whereby the OH group becomes attached to the carbon atom poorest in hydrogen (J. pr. Ch. [2] 64, 102, 387 ; comp. C. 1902, I. 1316) : CH2 CH8C1 || +HOC1= | C(CH3)2 C(CH8)2OH (3) By the action of halogen acids on ethylene oxide and its homologues : CH2.OH +HC1=| CH2C1 (4) Synthetically, it can be prepared from haloid ketones or haloid car boxy lie esters and alkyl magnesium halides (B. 39, 225, 3678 ; C. 1906, I. 1584, II. 1179) : CHjCO CH,Mgl (CH3)2COH CHa.CH2I C2H6Mgl CH2CH2I CH2C1 CH2Cl' C02R (C2H6)2COH Similarly, a-Chloro-fi-ethoxybutane, C1CH2CH(C2H6O)C2H6 is prepared from aj8-dichlorethyl ether and zinc ethyl (B. 28, 3111). Glycol Chlorhydrin, Ethylene Chlorhydrin, CH2C1.CH2OH, b.p. 128°. Glycol Bromhydrin, b.p. 150°, results also from glycol bromacetin (p. 324) by boiling with methyl alcohol. Similarly Glycol lodohydrin, b.p.16 78°, is obtained from iodo- acetin (C. 1901, I. 1356). The iodohydrin is converted completely into acetalde- hyde when heated with lead hydroxide (C. 1900, II. 31). Trimethylene Glycol Chlorhydrin, y-Chloro-n-propyl Alcohol, CH2C1.CH8CH8OH, b.p. 160°, is obtained 320 ORGANIC CHEMISTRY from trimethylene glycol byHCl. a-Propylene Glycol a-Chlorhydrin, CH8CH(OH>- CH,C1, b.p. 127°, is prepared from alkyl chloride by dilute sulphuric acid ; also by the addition of HC1O topropylene, a-Propylene Glycol fi-Chlorhydrin,CHdCHCl.- CH8OH, b.p. 134° (C. 1903, II. 486). Isobutylene Glycol a-Chlorhydrin, (OH)C- (CH3)2CH2C1, b.p. 129°, is obtained from chloracetone or monochloracetic acid by Mg(CH3)I ; also from isobutylene and HC1O (C. 1902, I. 1093). Isobutylene oxide and HC1 gives a mixture of this chlorhydrin and Isobutylene Glycol fi-Chlor- hydrin (CH3)2CC1.CH2OH, which easily passes into isobutyl aldehyde (B. 39, 2789, 3678). The primary haloid esters can also be considered as substitution products of the monohydric alcohols. Glycol chlorhydrin • would be chlorethyl alcohol. (i) Nascent hydrogen converts them into primary alcohols. (2) Oxidizing agents convert them into halogen fatty acids, e.g., glycol chlorhydrin yields monochlor- acetic acid ; trimethylene glycol chlorhydrin yields fi-chloropropionic acid. (3) They change to alkylene oxides, and partially also into aldehydes, under the influence of alkalis. (4) Basic esters of the glycols are produced when they combine with salts of organic acids ; e.g., glycol chlorhydrin and potassium acetate yield glycol mono-acetate, CH3COO.CH2.CH2OH. (5) Potassium cyanide changes them to nitriles of the hydroxyacids. The Ethers of the glycol brom- and iodohydrin can be employed in the building up of the neutral dialkyl ethers of the higher glycols (comp. p. 310). In close relation to the halohydrins stand certain substances produced by the action of mercury salts on ethylene (p. 82), such as Mercury Ethanol Iodide, HOCH2.CH2HgI, and Mercury Ether Iodide, O(CH2CH2HgI)2. Iodine changes them to Glycol Iodohydrin (p. 319) and fi-Diiodo-ether, O(CH2CHaI)2. Alkaline stannic solutions react with mercury ether bromide producing Mercury Diethylene Oxide, O(CH2.CH2)2Hg, m.p. 145°, a very stable compound, which requires fuming hydrochloric acid to decompose it, generating ethylene (B. 33, 1641 ; 34, 1385, 2910). Neutral Haloid Esters of the glycols are very important parent bodies for the preparation of the glycols (comp. methods i and 4 for the formation of glycols, p. 309). Methods of Formation. — (i) By the addition of halogens to the olefines — e.g., ethylene gives rise to ethylene chloride, bromide and iodide : CH2 CH2C1 CH2 CH2Br CH2 CH2I il +C12=| ; || +Bra=| ; || +Ia=| : CH2 CH2C1 CH2 CH2Br CH2 CH2I (2) by substitution in paraffins and monohalogen paraffins : CH3 C12 CH2C1 C12 CH2C1 CH3 CH3 <Fe> ^ CH2Cl' (3) by the addition of halogen acids to monohalogen olefines. In this instance much will depend on the temperature, concentration, and other conditions, as to whether both or only one of the two possible isomers is formed : CHBra dil. HBr CHBr Cone. HBr CH2Br. AH. (4) by the action of HC1, HBr or HI on glycols and glycol halo- hydrins. The second OH group will be replaced with more difficulty, and at a higher temperature, than the first. Similarly, the glycol ethers (p. 316) are converted into the dihalides by an excess of halogen acid. (5) Alkylene diamines or halogen alkyl monoamines yield alkylene dihalides, either by the action of nitrosyl chloride or bromide (C. 1899, 1. 25) ; or better by warming the benzoyl derivative of the amide ESTERS OF THE DIHYDRIC ALCOHOLS OR GLYCOLS 321 with phosphorus chloride or bromide, and distilling the resulting imide chloride or bromide (v. Braun, B. 38, 2346 ; 39, 4112) : The benzoyl derivatives of the cyclic imines, such as benzoyl piperidine, benzoyl pyrrolidine (comp. p. 335), yield dichloro- and dibromo-paraffin and benzonitrile by breakage of the ring, under the action of PC15 or PBr6. This constitutes a convenient method of preparing i,5-dichloro- and dibromopentane. (6) by the action of PC15 on glycols : (7) by the action of KI on alkylene bromides, producing iodides ; and HgCl2, producing chlorides. Properties. — The simple dichlor- and dibrom-esters of the glycols, or olefine dichlorides and dibromides, volatilize without decom- position. The di-iodides decompose readily in the light, and when distilled break down into ole fines and iodine. The ethylene dihalides have a very pleasant odour. Reactions. — (i) The dihalogen paraffins are converted into ole fines by sodium : CH2C1 CHCla 2Na CH, I and | - > || • CHaCl CHa CH, The production of trimethylene from trimethylene bromide and sodium or zinc is noteworthy : yCHaBr yCH2 CH,< +2Na=CH2< I +2NaBr. \CHaBr \CH2 (2) Nascent hydrogen converts both di- and mono-halogen paraffins into paraffins. This is the reverse of substitution — retrogressive sub- stitution (p. 93). (3) When digested with alcoholic potassium hydroxide, halogen hydride splits off, acid molecules are lost, and monohalogen olefines and acetylenes or diolefines result (p. 86). (4) Suitable reagents change dihalogen paraffins into the corre- sponding glycols (p. 309) or their esters. Heating with water produces first the mono-halogen hydrines of the glycols, and finally ketones and aldehydes. The 1,4- and i,5-dihalides yield also cyclic oxides (comp. 