Affiliation:
1. Modeling and Calculation Methods Laboratory University Dr. Moulay Tahar of Saida B.P. 138 20002 Saida Algeria
Abstract
AbstractThe investigation of experimental pKa values in liquid ammonia at room temperature for a series of 30 organic compounds containing eight distinct chemical groups enabled an accurate assessment of the proton ammoniation free energy. The deprotonation free energies, as well as the solvation free energies of acids and conjugate bases, were computed using a combination of quantum chemical and electrostatic approaches. Two thermodynamic schemes were employed to reproduce experimental pKa values while scanning a large interval of probable values of proton ammoniation free energy. The desired quantity corresponded to the lowest mean absolute deviation of the overall reproduced pKa values of the series. As a result, the proton ammoniation free energy was evaluated to be −275.0 Kcal/mol. Test results show that this proposed value is well suited for pKa calculation in liquid ammonia at room temperature.