Directive effects in benzylic hydrogen atom abstraction—II : Radical chlorination by sulphuryl chloride

Abstract

Relative reactivity values for benzaldehyde, deoxybenzoin, alkylbenzenes and cyclohexane toward sulphuryl chloride have been measured at 40° in carbon tetrachloride. The values (per α-H atom) for ethylbenzene, cumene and diphenylmethane, and that for cyclohexane relative to toluene are found to be significantly different from those reported for photochlorination under similar conditions, α-Chlorination of substituted toluenes relative to cyclohexane and of substituted ethylbenzenes relative to m-chlorobenzaldehyde by sulphuryl chloride in dilute CCl 4 solution at 40° has been measured and the results show a polar effect with ϱ-values of −0·56 and −0·49, respectively, correlated by σ constants. Although the relative reactivity data for alkylbenzenes can probably be interpreted as evidence for H abstraction mainly by the chlorosulphinyl radical the reaction constant ϱ found for the toluene system cannot be utilised to identify the principal H-abstracting species. Nevertheless, abstraction by the “π-complexed” Cl atom has been ruled out under the condition studied.