Calculating partition coefficient by atom-additive method

A new atom-additive method is presented for calculating octanol/water parti tion coefficient (log P) of organic compounds. The method, XLOGP v2.0, give s log P values by summing the contributions of component atoms and correcti on factors. Altogether 90 atom types are used to classify carbon, nitrogen, oxygen, sulfur, phosphorus and halogen atoms, and 10 correction factors ar e used for some special substructures. The contributions of each atom type and correction factor are derived by multivariate regression analysis of 18 53 organic compounds with known experimental log P values. The correlation coefficient (r) for fitting the whole set is 0.973 and the standard deviati on (s) is 0.349 log units. Comparison of various log P calculation procedur es demonstrates that our method gives much better results than other atom-a dditive approaches and is at least comparable to fragmental approaches. Bec ause of the simple methodology, the `missing fragment' problem does not occ ur in our method.