Kinetics of the bromination of some aromatic amines in aqueous perchloric acid

Abstract

The rates of bromination of 2,6-diethylaniline, 2,4-dimethylaniline, 2,6-dichloroaniline, and 2,4-dichloroaniline have been measured over a wide range of acidities in aqueous perchloric acid, and that of 4-bromo-N-dimethylaniline in aqueous sulphuric acid. The effect of bromide ion concentration at constant acidity was also studied for the four primary amines. The inverse acidity dependence follows either H₀ or H₀‴ according to whether the amine is primary or tertiary, and for 4-bromo-N-dimethylaniline there is an additional inverse dependence upon the water activity. The effect of bromide ion concentration shows that at low bromide-ion concentrations the rate-determining step for the primary amines is the reaction between molecular bromine and undissociated amine. At higher bromide-ion concentrations the decomposition of the Wheland intermediate becomes partially rate-determining.