Rate acceleration by steric inhibition to solvation of sulphur nucleophiles in acyl transfer processes. A comparison of steric effect in nucleophilic substitutions at carbonyl and aromatic carbon atoms

Abstract

On increasing the size of the alkyl group in the ortho-position of benzenethiol from methyl to t-butyl the nucleophilicity of benzenethiolate is found to increase in carbonyl carbon atom substitution and to decrease in nucleophilic aromatic substitution; steric inhibition to solvation of the anionic sulphur nucleophile is invoked to account for the rate-accelerting steric effect.