GB837429A - Preparation of aliphatic carboxylic acids - Google Patents

Abstract

Saturated aliphatic monocarboxylic and dicarboxylic acids are prepared by reacting, at a temperature at which the reactants are fluid, a molten alkali metal hydroxide with a saturated aliphatic carboxylic acid containing 16-22 carbon atoms, exclusive of the carbon atoms in the cyano or acyloxy substituents specified below, or an ester of said acid and a monohydric or polyhydric alcohol, the acid or ester also containing in its acid chain (a) at least one group having the formula <FORM:0837429/IV (b)/1> in which X is chlorine or bromine and Y is an hydroxy or an -OCOR group in which R is hydrogen or a C1-C5 alkyl group, or (b) at least one group having the formula <FORM:0837429/IV (b)/2> dissolving the resultant mixture of salts in water and acidifying the aqueous solution formed to liberate the free acids. The fusion is preferably effected in the presence of an inert liquid such as a mineral oil. The reagents containing the (a) type groups are preferably added to the molten caustic reagent at about 270-400 DEG C., while those containing (b) type groups are preferably added at about 200-400 DEG C.; water may be added to facilitate fusion of the caustic alkali. Superatmospheri pressures may be used. The preferred working up comprises dissolving the cooled product in water, extracting the solvent if present with, for example, diethyl ether or petroleum ether, acidifying the aqueous solution with a mineral acid and extracting the mixture of mono- and di-basic acids with, for example, diethyl ether and stripping off the solvent. The mono- and dibasic acids may be separated from one another by dissolving the fusion product in water or the recovered acid mixture in dilute caustic alkali, adding an organic solvent such as octane and acidifying to a pH not below about 5.5; the organic layer now containing the monobasic acids is removed and the solvent distilled off. The aqueous layer is further acidified to about pH 1.5-2 and the precipitated dibasic acids are filtered off. Individual acids may be separated by chromatography. The acyloxyhalo acids and esters used as starting materials may be prepared as described in Specification 770,585 and the cyano-hydroxy acids and esters may be prepared as described in Specification 837,430; numerous starting materials for the preparation of these compounds are given including oleic, linolenic and palmitolenic acids and esters of such acids with numerous alcohols such as methyl, butyl, 2-ethyl hexyl, cyclohexyl and benzyl alcohols, ethylene glycol, diethylene glycol, dodecane diol-1, 12, glycerol and pentaerythritol and various fats and fatty oils including tallow. The hydroxy-halo acids and esters used as starting materials may be prepared by alkaline hydrolysis of the acyloxyhalo acids and esters referred to above. In typical examples: (1) a mixture of 9,10- and 10,9-formoxychloro stearic acids is slowly added to a mixture of potassium and sodium hydroxides heated to 320-330 DEG C. and the product is then dissolved in water and strongly acidified; the recovered mixed acids are separated as above described into monobasic acids and dicarboxylic acids comprising azelaic and sebacic acids; (2) the same products are obtained by adding a mixture of 9,10- and 10,9-hydroxy chlorostearic acids to a mixture of KOH, NaOH and a mineral oil at 315-320 DEG C., ethereally extracting the mineral oil from the product and then working up as in (1); the formoxychloro derivative of commercial tallow (which comprises oleic acid) and methyl formoxychloro stearate may be treated in the same manner; (6) a mixture of 9,10-cyanohydroxy and 10,9-cyano hydroxy stearic acids, and the cyano hydroxy derivatives of (7) the methyl esters of rape seed oil acids and (8) tallow are treated according to the method of (6). Reference is made under section 9 of the Patents Act 1949 to Specification 706,650.