Studies on the Rate of Hydrolysis of Sec-Butyl P-Toluenesulfonate

The rate of hydrolysis of sec-butyl p-toluenesulfonate has been investigated in different solvent mixtures of acetone and water and dioxane and water. The mechanism of the hydrolysis of this ester, which is similar to the secondary alkyl halides, is situated on the border line between the unimolecular dissociation and the bimolecular displacement. It has been found that the rate is proportional to a certain function of the dielectric strength of the solvent but that the proportionality factor is much larger when the solvating power of the medium is high. By studying the ionic strength effect, the so called "mass law effect", and the hydroxyl ion influence on the rate, one has come to the conclusion that both un1molecular and bimolecular mechanisms are involved in this hydrolysis. For low values of the dielectric constant of the medium, the bimolecular mechanism seems to be present to the larger extent while for high values of this function the unimolecular dissociation is predominant.