Feasibility of the spontaneous gas-phase proton transfer equilibria between neutral Brønsted acids and Brønsted bases

The computational investigation of interactions of different acid–base pairs regarding the nature and extent of spontaneous proton transfer was carried out at B3LYP/6-311 + G** level. The selected acid–base pairs include the interactions of strong base (K2O) with acids of different strength (HClO4, HCl, and HF), and strong acid (HClO4) with bases ranging from K2O (GB = 322.8 kcal/mol) to H2O (GB = 157.6 kcal/mol). It was shown that spontaneus, unassisted proton transfer can take place in the gas-phase reactions of strong neutral Bronsted acids and bases. The reaction might be barrierless as in case of interactions between strong acids and bases, for example perchloric acid and alkali metal oxides or potassium oxide and halogen hydrides, or involve the encounter complex (hydrogen bonded acid–base cluster), which is separated from ion-pair by the transition state. Copyright © 2008 John Wiley & Sons, Ltd.