Investigation of tautomeric A—H ⋯ B ⇌ A–⋯ H—B+ equilibrium by linear and non-linear dielectric polarization

Abstract

Proton motion within the hydrogen bond is discussed, and the non-linear dielectric effect is used to check the tautomeric equilibrium hypothesis of two equilibrium positions of the proton. The results of this investigation lead to the conclusion that the simultaneous existence of tautomers with a lifetime longer than the dielectric relaxation time is highly doubtful. The results, however, are in good agreement with the charge transfer model of the hydrogen bond as well as with the proton transfer model which has a very low activation barrier or rapid proton tunneling in the hydrogen bridge.