The components of the "critical quartet" log Kow values assessed by four commercial software packages

Partition coefficient (log K_ow) values of 103 compounds in four different solvent-water systems (alkane-water, octanol-water, chloroform-water and propylene glycol dipelargonate (PGDP)-water - the "critical quartet") were published by Leahy et al. (1992). J. Chem. Soc. Perkin Trans. 2, pp. 723-731. They used the Abraham LSER (linear solvation energy relationship) descriptors to model the log K_ow values in the four systems. The calculation of Abraham LSER descriptors has now been computerized in the ABSOLV program, and we have used ABSOLV, and three other commercial software packages (HYBOT-PLUS, Molecular Modeling Pro and QsarIS) that calculate descriptors of similar classes, to model partitioning in the four solvent-water systems. Stepwise regression selected broadly similar types of descriptor from each software package to model log K_ow values in each solvent-water system. Overall, HYBOT-PLUS gave the best results. The rôle of the various classes of descriptor (size, polarity, polarizability, hydrogen bonding) in modeling partitioning in the four different solvent-water systems is discussed.