Polar influences in radical reactions. Part V. Hydrogen abstraction from nuclear-substituted ethylbenzenes and benzhydryl methyl ethers by atomic bromine

Abstract

The relative rates of hydrogen-abstraction by atomic bromine (from N-bromosuccinimide) at 80° have been determined for nuclear-substituted ethylbenzenes and benzhydryl methyl ethers, by means of intermolecular competitive reactions using, respectively, benzhydryl methyl ether and dibenzyl ether as reference standards. The results show, in the former series, a polar effect (ρ=–0·69) correlated by the σ⁺constants, and, in the latter series, the absence of such an effect.

In attack by atomic bromine on the systems toluene, ethylbenzene, benzaldehyde dimethyl acetal, benzyl methyl ether, dibenzyl ether, and benzhydryl methyl ether, data are presented to show that the ρ-values bear a consistent inverse relationship to the relative reactivities of the systems.