Polar influences in radical reactions. Part VI. Hydrogen abstraction from nuclear-substituted ethylbenzenes, benzaldehyde dimethyl acetals, and diphenylmethyl methyl ethers by the trichloromethyl radical

Abstract

The relative reactivities of nuclear-substituted ethylbenzenes, benzaldehyde dimethyl acetals, and diphenylmethyl methyl ethers toward the trichloromethyl radical at 80° have been determined by means of intermolecular competitive reactions. The results show a σ⁺ correlation by the Hammett equation with ρ-values of –0·53, –0·18, and –0·12, respectively, a decreasing polar effect consistent with the increasing reactivity of the three series.

Relative reactivity data are presented to show that atomic bromine and the trichloromethyl radical exhibit similar selectivity in abstraction of benzylic hydrogen atoms. In contrast to atomic bromine, the ρ-values found for the trichloromethyl radical in a number of systems bear no consistent inverse relationship to the relative reactivities of these systems.