ChemPhysChem, 19, 2486-2491 (2018)

DOI: 10.1002/cphc.201800518

Enhancement of Thermodynamic Gas‐Phase Acidity and Basicity of Water by Means of Secondary Interactions

A series of A⋅water, B⋅water complexes (A=acid, B=base) are studied at the G4 level of theory to show that water acidity or basicity can be modulated by non‐covalent interactions. Protic and non‐protic acids interacting with water form hydrogen bonds or other kinds of non‐covalent interactions, respectively, that may dramatically change the acidity of water up to almost 360 kJ ⋅ mol−1 in terms of enthalpy. Similarly, hydrogen bonds responsible for the interaction between typical small nitrogen‐containing Lewis bases and water can enhance the proton affinity of water by almost 300 kJ ⋅ mol−1. Our results reveal that these large enhancements are linearly related with the binding energy of the charged complexes, and are determined by the Lewis acid−base properties of the molecule involved in the interaction, allowing a quite precise modulation of the corresponding acid−base properties of water.