Rotational enhancement of the proton-transfer barrier for ion—molecule reactions on a double-minimum surface

Abstract

Experiments indicate that the methanol/methoxide proton-transfer reaction is slower than expected. Quantum calculations indicate that the barrier for proton-transfer within the ion—molecule dimer{CH 3OH…OCH 3]s] − → {CH 3O…HOCH 3} − is strongly dependent on the oxygen—oxygen separation. We show that the dimer is formed with high orbital angular momentum and that this can lead to elongation of the O—O distance. The proton-transfer transition state with conservation of orbital angular momentum is ≈ 1 kcal mol − higher than the saddle point.