The kinetics and mechanism of the electrophilic substitution of heteroaromatic compounds. Part XIV. Rates of acid-catalysed hydrogen exchange of para-substituted anilines and heterocyclic analogues
Abstract
Acid-catalysed hydrogen exchange of 4-substituted anilines occurs ortho to the amino-group in the free-base species, and is correlated by σm+ constants with ρ=–3·51. The corresponding σm+ constants for the NH+ and N+(OH)– heterocyclic groups are found to be 1·82 and 1·99 respectively. These are discussed and compared with previous σ constants for these groups.