A SEMIEMPIRICAL METHODOLOGY APPLICABLE TO THE ACCURATE CALCULATION OF HYDRATION ENTHALPY OF ORGANIC-MOLECULES

A semi-empirical methodology is introduced for calculating the hydration enthalpy of organic molecules. The enthalpy term is decomposed into electrostatic and non-electrostatic contributions. The former is calculated on the basis of a reaction field theory developed in our previous studies. The theory is combined with the MNDO method, The non-electrostatic contributions are estimated using empirical equations derived from experimental data for some nonpolar molecules. For typical cation, anion and neutral molecules, an excellent correlation is found between the calculated and observed hydration enthalpies.