Solvolysis of covalent arylsulfonylmethyl perchlorates. General base catalysis by dipolar, aprotic solvents

The dynamic basicity of Me2SO and Me2SO--H2O mixtures was studied employing the rates of irreversible deprotonation of two carbon acids as a kinetic probe. Upon the gradual addition of Me2SO to water, a continuous and strong rate of reaction was observed until at mole fraction of water, n/sub H2O/ = 0.62, the rate became too fast to be measured with the available kinetic equipment. The small change of the magnitude of the primary kinetic deuterium isotope effect (k/sub H//k/sub D/) as a function of n/sub H2O/ indicates that in the Me2SO-rich mixtures the mechanism of hydrolysis does not change from a base-catalyzed process to nucleophilic substitution