When carefully cooled and brought into contact with bromine, a dimethacetyl bromide, or dimethglyceryl tribromide: is produced, forming colourless elastic needles of camphor-like odour. It is soluble in ether and warm alcohol. Dimethyl-allyl bromide combines with chlorine to form dimethyl-glyceryl brom-dichloride: (CH3)2: CCI.CHCI.CH2Br. On heating the above isoamylene dibromide with potassic acetate in alcohol solution, a brom-isoamylene diacetate, CH,Br(O.C2H3O) 2, is produced, which yields, on saponification, brom-isoamylene dihydrate, CH,Br(OH)2, from which the bromine may be removed by long heating with potassic hydrate, giving Isoamyl glycerine, or dimethyl glycerine: CH3 CH3 C.OH CH.OH CH.OH CH2.OH This is a thick liquid, soluble in water, and of a sweet, aromatic taste. 702. Pseudo-Diallyl Alcohol-When diallyl is heated with hydric iodide, a compound of diallyl with two molecules of hydric iodide (§ 491, 2) is formed, and also a compound containing but one molecule of HI, thus: CH2:CH.CH2.CH2.CH: CH2 + HI = CH2:CH.CH2.CH2.CHI.CH3. This iodide boils at 164°-165°, and is converted on heating with argentic acetate into the salt CH2:CH.CH2.CH(O.C2H2O)CH3 (boiling point 150°-160°), which gives on saponification pseudo-diallyl alcohol, CH2: CH.CH2.CH2.CH(OH).CH,, an oily liquid boiling at 140° and of sp. gr. 8625 at 0°. The corresponding triatomic or trihydric alcohol: CH2(OH).CH(OH).CH2.CH2.CH(OH).CH3, has not yet been prepared. 405 DERIVATIVES OF THE TETRAVALENT HYDROCARBON NUCLEI, CnH2n-2 COMPOUNDS OF THE ALCOHOL ACID RADICALS, CnH2n- 703. By replacement by hydroxyl of one of the hydrogen atoms of the alcohol radical contained in a fatty acid, compounds are obtained which combine the characters of a monobasic acid with that of a monacid alcohol, the hydroxy fatty acids: CnH2n'.OH CO.OH According to the position of the hydroxyl on the carbon nucleus, primary, secondary, or tertiary alcohol acids are obtained : If the nucleus contains three or more carbon atoms, the proximity or otherwise of the hydroxyl and carboxyl groups causes isomerism, which, according to the degree of proximity, are termed a-, ß-, 7-, &c., derivatives: 704. The alcohol and the acid hydroxyl groups can be replaced by other elements (halogens) or radicals (amides, &c.) in similar manner to the replacement of the hydroxyl groups of acids or alcohols; further, the hydrogen atoms can be replaced by metals and the radicals of acids and alcohols. -2. 705. The following are amongst the most generally applicable methods of preparation : 1. Those of the glycols which contain the primary alcohol group, CH2.OH, at least once, are converted into hydroxy-acids on gentle oxidation, as by atmospheric oxygen in presence of platinum black or by dilute nitric acid : = CnH2n(OH).CH2.OH + 20 H2O + CnH2n(OH).CO.OH. 2. The hydroxy-aldehydes (§§ 653 and 656) absorb oxygen from the air and reduce the oxides of noble metals: CnH2n(OH).CO.H+0=CnH2n(OH).CO.OH. 3. The fatty acids yield mono-substitution products on heating with the halogens, and, when the nucleus contains at least three carbon atoms, give the a derivative in by far the greatest quantity CH3.CH.CO.OH + Br2 = HBr + CH3.CH Br.CO.OH Propionic acid. a On long boiling the alkali salts of these latter, they decompose into metallic haloid and hydroxy-acid : CH.CL.CO.OK + HOH = KCl + CH2(OH).CO.OH, the process occurring in shorter time in presence of free alkali : CH¿CI.CO.OK + KOH = KCl + CH2(OH).CO.OK. 4. The aldehyde and ketone acids derived from the pentavalent nucleus CnH2n-3 (see later) combine with hydrogen and are converted into hydroxy-acids, the first into primary, the second into secondary alcohol acids: 5. The aldehydes can be converted, with nucleus synthesis, in two ways into secondary a-alcohol acids. a. Aldehydes unite directly with hydro-cyanic acid to form an alkylidene hydrate cyanide : CH3 CH3 + HCN=CH.OH CH:0 CEN which, like all nitriles, is decomposed on warming with acids, yielding an ammonic salt and the secondary a-hydroxyl acid : CH3 = CH3 CEN CO.OH b. Aldehyde ammonias (§ 422) are readily converted into alkylidene amid cyanides by action of prussic acid: The latter are converted by dilute mineral acids into acid derivatives of a-amidated fatty acids: from which the secondary a-hydroxy-acid can be obtained by action of nitrous acid (comp. § 266): CH.NH, + NO.OH = H2O + N2 + CH.OH CO.OH CO.OH The secondary a-hydroxy-acids are therefore alkylidene hydrate carbonic acids: он C1H2n+1.CH {CO.OH 6. Tertiary a-hydroxy-acids can be prepared in similar manner from the ketones when a mixture of ketone and hydro-cyanic acid is decomposed by a mineral acid: 7. In similar manner to the formation of fatty acids from the alkyl haloids of next lower carbon contents the alcohol acids can be obtained from the olefine hydrate haloids (§ 493). The latter combine with potassic cyanide to olefine hydrate cyanides: CH2(OH).CH2Cl + KCN = KCl + CH2(OH).CH.CN, and from these, olefine hydrate carbonic acids, which must be at least B-oxy-acids, are readily obtained: CH2(OH).CH2.CN + HCl + 20H2 = CH2(OH).CH2.CO.OH + NH,Cl. 8. A method of very general application for the formation of tertiary a-alcohol acids consists in the decomposition of neutral ethereal oxalates with zinc dialkyls. If they are mixed together, or if the oxalate be heated with an alkyl iodide and zinc, and the product decomposed by water, the ethereal salt of a tertiary hydroxy-acid separates: C2H, C2H2 5 706. On heating in sealed tubes with concentrated hydriodic acid the alcohol acids are reduced to the fatty acid of like carbon nucleus : By dry distillation, or better by heating with dilute sulphuric acid, the a-hydroxy-acids are split up into formic acid and an aldehyde (secondary) or a ketone (tertiary): CnH2n+1.CH(OH).CO.OH = CnH2n+1.CH:0 + H.CO.OH (CnH2n+1)2.C(OH).CO.OH = (CnH2n+1)2CO + H.CO.OH. If oxidising agents are also present the formic acid is in great part converted into carbonic anhydride, the aldehyde into the corresponding fatty acid. 707. A peculiar property of the oxy-acids consists in their power to form two different ether-like derivatives when gently warmed with acids for some time, or by long standing in a perfectly dry atmosphere. Two molecules then so behave that one acts as an alcohol, the other as an acid: This first ethereal anhydride is at once both alcohol and monobasic acid, and is slowly decomposed by water into two molecules of the oxy-acid, or quickly by alkalies yielding salts of the latter. In dry |