Nucleophilic substitution at two-co-ordinate sulphur. Brønsted relationships with nitrogen nucleophiles
Abstract
The rate of reaction of p-nitrophenyl triphenylmethanesulphenate with a variety of amines has been measured in 45% dioxan–water. The kinetic data, plotted in a Brønsted fashion against the pKa of the conjugate acid of the nucleophile, yield linear relationships characterized by β= 1·5 for anilines, 0·84 for pyridines, 0·75 for secondary heterocyclic amines, and 0·58 for primary aliphatic amines. The large effect of the basicity of the nucleophile on the rate of reaction is interpreted in terms of large bond formation in the transition state and the much larger slope found for anilines is discussed.