The Influcence of the Solvent on Reaction Velocity. XXIV. The Acid Hydrolysis of Ethyl Acetate in Dimethyl Sulphoxide-Water Mixtures.

Abstract

The rate of alkaline hydrolysis of carboxylic esters usually decreases with decreasing water concentration in mixtures of water and an organic solvent. In contrast to this, the rate of alkaline hydrolysis of ethyl acetate in dimethyl sulphoxide-water mixtures increases with increasing dimethyl sulphoxide concentration, the enhancement being especially pronounced at high dimethyl sulphoxide concentrations. This increase is attributed to an increased activity of the hydroxide ion caused by its reduced solvation in the presence of dimethyl sul- phoxide. The relation between the dielectric constant of the solvent and the rate constant, the variation of deltaG *, deltaH* and TdeltaS* with solvent composition and the specific effect of water on the reaction are discussed.