Acidity constants from DFT-based molecular dynamics simulations

Abstract

In this contribution we review our recently developed method for the calculation of acidityconstants from density functional theory based molecular dynamics simulations.The method is based on a half reaction scheme in which protons are formallytransferred from solution to the gas phase. The corresponding deprotonation freeenergies are computed from the vertical energy gaps for insertion or removalof protons. Combined to full proton transfer reactions, the deprotonationenergies can be used to estimate relative acidity constants and also the BrønstedpKa when the deprotonation free energy of a hydronium ion is used as a reference. We verified themethod by investigating a series of organic and inorganic acids and bases spanning a wide range ofpKa values (20 units). The thermochemical corrections for the biasing potentials assisting anddirecting the insertion are discussed in some detail.