GB740747A - Preparation of alpha-omega-dicarboxylic acids - Google Patents

Abstract

Alpha-omega-dicarboxylic acids or esters thereof are obtained by reacting a cycloaliphatic peroxidic compound which is liquid at normal temperatures and pressures and in which the peroxide group is linked to a carbon atom which forms part of the cyclic ring which carbon atom is also linked to an exocyclic oxygen atom, with a ferrous salt in solution or suspension in an aqueous medium, in the presence of an added acid, the ferrous salt being employed in excess of the equivalent amount and the process being carried out at between 50 DEG C. and the freezing point of the mixture. The cyclic peroxidic compounds employed are preferably the compounds formed by treating cycloaliphatic ketones with hydrogen peroxide and such treatment may be carried out in the presence or absence of an acid, e.g. hydrochloric acid, as catalyst. The hydrogen peroxide may suitably be used in the form of a solution of concentration from 5 per cent upwards, advantageously in excess of 30 per cent and preferably of about 90 per cent concentration. The cyclic ketone may be a cycloparaffin- or substituted cycloparaffin ketone, e.g. cyclopentanone, cyclohexanone, cycloheptanone, or alkyl substituted, e.g. methyl-, ethyl-, or isopropyl-substituted cyclopentanone, cyclohexanone, or cycloheptanone. It is preferred to carry out the process by adding the peroxidic material gradually, with stirring, to the aqueous acid medium containing the ferrous salt, the reaction temperature being preferably maintained at about 0 DEG C. The aqueous acid medium may comprise an aqueous solution of an acid such as sulphuric acid or an acidified aqueous organic solvent solution such as aqueous alcohol to which acid has been added. The cyclic peroxidic compunds used may also be 1-alkoxy-cycloalkyl hydroperoxides which may be obtained by direct oxidation of alkoxy substituted aliphatic compounds. These hydroperoxides on being treated in accordance with the invention yield the esters of the dicarboxylic acids. The ferrous salt may be ferrous sulphate, ferrous lactate, or ferrous chloride and it is preferred to use two equivalents of the ferrous salt based on the cycloperoxidic compound used. In examples: (1) to (9) dodecane-1:12-dioic acid together with some cyclohexanone, caproic acid and other monobasic acids is obtained by treating cyclohexanone with hydrogen peroxide solution and adding the product gradually to a solution of ferrous sulphate in 2N sulphuric acid; (1) paramethylcyclohexanone is treated with 90 per cent hydrogen peroxide and the oily liquid formed is added to a solution of ferrous sulphate in 2N sulphuric acid to yield 4:9-dimethyldodecane-1:12-dioic acid together with some 4-methyl caproic acid and other monobasic acids; (11) cycloheptanone is treated with hydrogen peroxide containing a little hydrochloric acid and the product added to a solution of ferrous sulphate in 2N sulphuric acid to yield tetradecane - 1:14 - dioic acid together with some cycloheptanone and heptoic acid; (12) cyclopentanone is treated with hydrogen peroxide and the reaction mixture added to a solution of ferrous sulphate in 2N sulphuric acid to yield sebacic acid, valeric acid, and cyclopentanone; (13) 1-methoxycyclohexyl hydroperoxide obtained by the oxidation of methyl cyclohexyl ether is treated with ferrous sulphate in 2N sulphuric acid to yield the methyl esters of caproic acid and dodecane-1:12-dioic acid which on hydrolysis are converted to the free acids; (14) a peroxide concentrate obtained by the oxidation of dicyclohexyl formal is treated with ferrous sulphate as in (13) to yield dodecane-1:12-dioic acid. Reference has been directed by the Comptroller to Specification 697,506.