Substituent effect of the sulphinyl group in electrophilic aromatic substitution

Abstract

Partial rate factors have been determined for molecular chlorination in nitromethane and protodesilylation in H₂SO₄–AcOH mixtures of methyl phenyl and diphenyl sulphoxide. The electron-activating effect observed in molecular halogenation is interpreted in terms of polarization of the sulphoxide group in the transition state, induced by the electrophilic reagent. In H₂SO₄–AcOH mixtures K_rel for protodesilylation at the para-position of methyl phenyl sulphoxide is very low, possibly because of hydrogen bonding between the sulphinyl group and the acidic medium. For methyl phenyl sulphide, sulphoxide, and some other compounds the ground state electron densities at the para-position have been evaluated from their ¹³C n.m.r. spectra.