OMNISOL - FAST PREDICTION OF FREE-ENERGIES OF SOLVATION AND PARTITION-COEFFICIENTS

The SM5.0R model for predicting solvation energies using only geometry -dependent atomic surface tensions was developed previously for aqueou s solution. Here we extend it to organic solvents. The method is based on gas-phase geometries and exposed atomic surface areas; electrostat ics are treated only implicitly so a wave function or charge-model is not required (which speeds up the calculations by about 2 orders of ma gnitude). The SM5.0R model has been parametrized for solvation free en ergies of solutes containing H, C, N, O, F, S, Cl, Br, and I. The trai ning set for organic solvents consists of 227 neutral solutes in 90 or ganic solvents for a total of 1836 data points. The method achieves a mean unsigned error of about 0.4 kcal/mol when applied using gas-phase geometries calculated at either the Hartree-Fock level with a heteroa tom-polarized valence-double-zeta basis set (HF/MIDI!) or when applied using semiempirical molecular orbital gas-phase geometries. In relate d work. reported here, the parametrization for predicting aqueous solv ation free energies is also extended to include organic solutes contai ning iodine. This extension is based on eight solutes and yields a mea n unsigned error of 0.25 kcal/mol. The resulting SM5.0R model for solv ation energies in aqueous and organic solvents can therefore be used t o predict partition coefficients (including log P for octanol/water) f or any solute containing H, C, N, O, F, S, Cl, Br, and/or I.