Reaction orders and isotope effects in the reversible addition of water to 1,3-dichloroacetone in aqueous dioxan

Abstract

The kinetics of the reversible addition of water to 1,3-dichloroacetone have been studied spectrophotometrically in aqueous dioxan with and without the addition of catalysts (hydrogen chloride, perchloric acid, four carboxylic acids and 2,6-dichlorophenol). Reaction orders with respect to water were determined, and also kinetic isotope effects in systems containing 50 and 100 atom % of deuterium. It is concluded that the uncatalysed reaction involves a cyclic transition state containing two extra water molecules, one of which may be replaced by a molecule of catalyst. The dependence of the kinetic orders and isotope effects upon the nature of the catalyst is attributed mainly to differences in the hydration or other properties of the catalyst in the initial state. It is believed that proton movement is partly synchronous with the making or breaking of the carbon-oxygen bonds, but there is no evidence that more than one proton moves simultaneously.