Evaluation of Acid Dissociation Constants in DMSO and DMF by Quantum-Chemical Methods

Abstract

We have calculated total electronic energies (E) and Gibbs energies (G) of a large number of acids and their anions in water, dimethylsulfoxide, and dimethylformamide using the hybrid B3LYP functional DFT method in the 6-31++G(d,p) basis set, taking into account the solvent effect by the conductor-like polarizable continuum model method. A linear correlation has been found between the experimental values of acid dissociation constants (pKa) of different nature and the difference between anion and acid E values, and between pKa and the difference between anion and acid G values. The obtained correlations allowed us to evaluate the pKa values of both inorganic and organic acids. Such an evaluation is of special importance for nonaqueous solvents as it is quite problematic to determine these dissociation constants.