The kinetics and mechanisms of aromatic halogen substitution. Part 34. Comments on the physical interpretation of high kinetic orders in bromine

Abstract

Reactions of bromine with aromatic and with olefinic compounds in acetic acid show kinetic behaviour which varies with solvent and initial concentration of bromine, and can indicate the presence of one, or of more than one, molecule of bromine in the transition state. Additional kinetic disturbances can result from complexing of bromine with added, or with developing, bromide ion, from environmental (salt) effects, and from the reversible formation of a carbocation. Some of the important criteria necessary for interpretation of the results in terms of the composition of the transition state, and in particular of the number of bromine molecules concerned in the transition state, are analysed.