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 σ_m⁺ constants with ρ=–3·51. The corresponding σ_m⁺ 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.