Bromination of nitrosobenzene in carbon tetrachloride and iodine catalysis of bromine addition to ethyl cinnamate in carbon tetrachloride

Abstract

The Mechanism of Substitution. Many theories have been advanced in an attempt to explain the mechanism of aromatic substitution. Armstrong (l) drew attention to a suggestion by Williamson (2) that substitution might be preceded by a type of dissociation and an alternative suggestion by KeKule (3) that addition is the first step followed by cleavage. Hughes and Ingold (4) incorporated the latter addition mechanism in a generalized theory of aromatic substitution but rejected the dissociation theory of Williamson on the grounds that groups replaced are always too strongly held to undergo primary dissociation even in the most powerful ionizing solvents, Ingold and co-workers explained satisfactorily the mechanism of aromatic substitution by classifying reactions according to the electrical affinities of the reagents.