Inverse order of solvolytic reactivity for benzylic substrates containing electron-attracting aromatic substituents. A probe for the absence of resonance contribution of the α-aryl group to the cationic transition state

Abstract

An inverse order of reactivities, k_p/k_m > 1, for electron-attracting α-aryl substituents was observed in the solvolysis of highly crowded toluene-p-sulphonates (5) and p-nitrobenzoates (6), which could be used as a probe for the lack of significance of resonance contribution in the cationic transition state.