Thermodynamic and activation parameters in the reversible hydration of 1,3-dichloroacetone in dioxan

Abstract

The reversible hydration of 1,3-dichloroacetone in aqueous dioxan has been studied spectrophotometrically at 12 temperatures between 277 and 333 K. Rates and equilibrium constants were measured at two water concentrations for the uncatalysed reaction, and the rate of the reaction catalysed by benzoic acid was studied at a single water concentration. The enthalpy and entropy of hydration agree with previous results in aqueous solution, and the magnitude of the entropy change can be interpreted statistically. The entropy of activation for the uncatalysed reaction is consistent with a cyclic transition state containing two extra water molecules, and the less negative value for catalysis by benzoic acid supports the view that the catalyst replaces one water molecule in the transition state.