Kinetic studies of hydrogen exchange in substituted dialkylanilines. Part IV. Isotope effects and reaction mechanism

Abstract

Isotope effects in hydrogen exchange of dimethylaniline in acid solution have been investigated by measurement of exchange rates for tritiation, detritiation, deuteriation, and dedeuteriation in H₂O and D₂O. The results indicate that two distinct rate-limiting steps operate in the electrophilic substitution mechanism. The first is the transfer of a proton from solvent to substrate, the other being an intramolecular decomposition of a carbon conjugate acid ion intermediate. A correlation is observed between magnitude of isotope effect and specific rate constant.