The Hydration of Ketones in Mixtures of Water and Polar Aprotic Solvents

Abstract

The hydration of a series of ring-substituted trifluoroacetophenones (Z) has been studied by means of u.v. and n.m.r. spectroscopy in DMSO–water and sulfolane–water mixtures. The W0 function is defined as [Formula: see text] where Kd is the equilibrium constant for the reaction [Formula: see text]Mixtures of water and sulfolane in all proportions have a dehydrating effect compared to water but mixtures of water and DMSO down to 15 mol % water are more hydrating with respect to the carbonyl group of trifluoroacetophenones than is pure water. An analysis of activity coefficient behavior indicates that the diol, ZH2O, has a higher requirement for solvation by water molecules than does water itself.The rate of the uncatalyzed hydration in aqueous sulfolane drops drastically as the water content of the medium decreases, whereas the rate of the acid-catalyzed reaction is not greatly affected by changes in the solvent composition; a plot of log k for both catalyzed and uncatalyzed reactions is approximately linear in W0.