Model Study of the Acid−Base Proton-Transfer Reaction of the ClH···OH2 Pair in Low-Polarity Solvents

We present a theoretical study of a model of the ClH···OH 2 ⇌ Cl - ···HOH 2 + acid−base proton-transfer reaction in nonaqueous solvents with low dielectric constants. In this low-polarity environment, both the reactants and products of the proton-transfer reaction are observable. The electronic structure of the acid−base pair is treated via a two-state valence-bond description parametrized using a combination of experimental and ab initio data. The fundamental nature of this proton-transfer reaction is investigated with particular emphasis on the effects of quantization of the proton and hydrogen-bond vibrations. Vibrational wave functions in these coordinates are presented, along with coordinate expectation values and variances, and are placed in the perspective of the proton-transfer process.