GB647160A - Improvements in or relating to processes of producing alkyl esters of sulphonated monohydroxybenzoic acids - Google Patents

Abstract

The C6 to C18 alkyl esters of sulphonated ortho-, meta- or para-mono-hydroxy benzoic acid, wherein the alkyl group is attached to the carboxyl group, are prepared by reacting the corresponding lower alkyl ester with sulphur trioxide in sufficient quantity to at least produce monosulphonation and subjecting the sulphonated product to ester interchange with an aliphatic alcohol having from 6 to 18 carbon atoms in the molecule or mixtures thereof. By lower alkyl is meant alkyl groups containing from 1 to 5 carbon atoms. The methyl ester of the hydroxy benzoic acid may be employed and the rate of addition of sulphur trioxide is such that the temperature is kept between 23 DEG and 125 DEG C., preferably 90 DEG to 115 DEG C. A mixture of alcohols having an average molecular weight of about 186 may be employed. Salts of the above alkyl esters of sulphonated hydroxy benzoic acids are prepared by neutralizing the acids with an oxide, hydroxide or carbonate of an alkali or alkaline earth metal (including magnesium). In the examples, alkyl esters of sulphonated ortho hydroxy benzoic acid are prepared by sulphonating methyl salicylate and subjecting the product to alcoholysis with a mixture of alcohols comprising hexyl, octyl, decyl, lauryl, myristyl, cetyl, stearyl and oleyl alcohols.