Analyses of the partition coefficient, log P, using ab initio MO parameter and accessible surface area of solute molecules

To analyze the log Psol/w values (sol: n-octanol or chloroform, w: water) in the framework of the molecular orbital (MO) procedure, we selected solute descriptors such as the solvation energy difference between aqueous and organic solvent phases and the “surface” area of solute molecules to which water molecules are accessible. The solvation energy of solute molecules in their minimum free-energy conformation was calculated using the ab initio self-consistent reaction field-MO method with the conductor-like screening model. The experimentally measured log Psol/w value of various solutes except for those of amphiprotics was shown to be analyzable reasonably well by the MO model with additional descriptors for the hydrogen-bonding patterns in the solute–solvent interactions. © 2004 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 93:2681–2697, 2004