GB876487A - Preparation of acetonedicarboxylic acid and esters thereof - Google Patents

Abstract

Acetonedicarboxylic acid and C1-4 alkyl esters thereof are prepared by adding citric acid to over 95% concentrated sulphuric acid, without stirring, at a temperature from about 40 to about 65 DEG C., gradually adding oleum or sulphur trioxide to the reaction mixture, with stirring and maintaining the mixture in the aforesaid temperature range, the reactants being employed in amounts sufficient to react with substantially all of the water produced, and continuing the reaction until substantial amounts of acetonedicarboxylic acid are produced; if an ester is required a dry alkanol is added to the resulting mixture, preferably at 25-45 DEG C. The acid may be isolated by rapidly cooling the reaction mixture to about 0 DEG C. and then rapidly adding cold water or ice without causing the temperature to rise above about 10 DEG C. The ester may be isolated by quenching the reaction mixture in water, e.g. below 20 DEG C., preferably at a pH of about 1.5 to 6 (a weak alkali such as ammonia may be used to control the pH), and extracting with an organic solvent, e.g. benzene.