A method for calculating the pKa values of small and large molecules
A method was developed for predicting of the aqueous ionization constants (pKa) of organic molecules. The method is a based on empirically calculated physico-chemical parameters that are obtained from ionization site-specific regression equations.
The presentation starts with the description of the ChemAxon's pKa calculation method. It is built around the pKa of the monoprotic molecules that is calculated as the sum of the next three increments. The explanation includes that the pKa calculation of multiprotic molecules is governed by a theoretically derived kinetic equations in our model and it describes the effect of tautomerization and resonance that can be taken into account in pKa prediction. You can read about the acidic and basic groups that are available in the ChemAxon's pKa model. Afterwards the presentation goes for the title topic and defines the small and large models of pKa calculations that is followed by a testing of these models. The implementation of the ChemAxon's pKa calculator to the company's Marvin and JChem software suits is described in the last part of the presentation.
American Chemical Society Spring meeting, March 25-29th, 2007