GENERAL SEMIEMPIRICAL QUANTUM-MECHANICAL SOLVATION MODEL FOR NONPOLARSOLVATION FREE-ENERGIES - N-HEXADECANE

A new solvation model has been developed that accurately predicts solv ation free energies in the nonpolar solvent n-hexadecane. The model is based on AM1-CM1A and PM3-CM1P partial charges, and it is based on a single set of parameters that is applicable to both the AM1 and PM3 Ha miltonians. To take account of both short-range and long-range solvati on-shell interactions, each atom has two surface tensions associated w ith different effective solvent radii. For hydrogen, one of these surf ace tensions depends on the bond orders to carbon, nitrogen, oxygen, a nd sulfur, although only weakly. In addition to presenting the general parameterization, the article provides an analysis of the surface ten sion parameterization based on data for three rare gases. The model yi elds an rms error of 0.41 kcal/mol over a set of 306 data points (153 molecules, two Hamiltonians) that includes alkanes, alkenes, alkynes, aromatics, alcohols, ethers, aldehydes, ketones, esters, amines, nitri les, pyridines, thiols, sulfides, fluorides, chlorides, bromides, iodi des, water, and ammonia.