GB697506A - Preparation of dibasic carboxylic acids - Google Patents

Abstract

Aliphatic dicarboxylic acids are prepared by treating with reducing agents the peroxides obtainable by the action of hydrogen peroxide on cyclic ketones R=C=O, R being a divalent radical of 3-9 carbon atoms (excluding substituents). Suitable reducing agents are compounds of metals showing more than one valency (e.g. iron, cobalt, manganese, copper, chromium), ascorbic acid, sodium formaldehyde sulphoxylate, sodium bisulphite and reducing sugars. Mixtures of such may be used, especially a ferrous salt with another reducing agent. The reaction may be carried out in water or organic solvents at - 100 DEG to + 100 DEG C., preferably in the absence of oxygen. It is desirable to mix the reactants rapidly, e.g. by dissolving each separately in a common solvent before mixing. The process may be carried out batchwise, semicontinuously or continuously, in the latter case by mixing the materials in a tubular reactor under conditions of turbulent flow. The dibasic acids can be isolated by distillation, ion-exchange or extraction, or by conversion into salts or esters. In an alternative process the alkyl ethers of the peroxides are reduced to give diesters of the acids, which can then be hydrolysed. Examples show the production of sebacic acid and dodecan-1 : 12-dioic acid from cyclopentanone peroxide and cyclohexanone peroxide respectively, reduction being carried out with ferrous sulphate, l-ascorbic acid and ferrous chloride. In one case an emulsion of the peroxide, benzene, water, sodium lauryl sulphate and sodium dihydrogen phosphate is treated with a mixture of sodium formaldehyde sulphoxylate and ferrous sulphate; the acid is recovered from the benzene phase. Many suitable radicals are specified for R in the above formula, which may be substituted with hydrocarbon radicals, chlorine, fluorine, hydroxyl, methoxyl, carboxylic acid, carboxylic ester or ketonic groups. Peroxides suitable for the above process may be prepared by reacting cyclic ketones with hydrogen peroxide or by oxidizing cyclic secondary alcohols with molecular oxygen in the presence of a free radical initiator such as ultraviolet rays or an azonitrile. In examples: (1) cyclopentanol is irradiated in the presence of oxygen, benzoin and calcium carbonate; (2) cyclohexanol is irradiated in oxygen. The products are probably 1-hydroxy-11-hydroperoxy-dicycloalkyl peroxides though other possible formul are given. The alkyl ethers of peroxides mentioned above are obtained by treatment of alkyl ethers of cyclic secondary alcohols with oxygen, preferably in the presence of free radicals.