Ab initio calculations of pKa values of some organic acids in aqueous solution

The acidity of different classes of organic compounds in aqueous solution has been calculated. The calculations are carried out at the SCF level with inclusion of entropic and thermochemical correction to yield free energies of dissociations. The polarized continuum model is used to describe the solvent. The model furnishes pK(a) values in relatively good agreement with experimental data. Scaling different parts of solvation energies provides a significant improvement in results and signifies the importance of balance of individual contributions from electrostatic, cavity, dispersion and repulsion interactions. (C) 2002 Elsevier Science B.V. All rights reserved.