Calculating partition coefficient by atom-additive method

A new atom-additive method is presented for calculating octanol/water partition coefficient (log P) of organic compounds. The method, XLOGP v2.0, gives log P values by summing the contributions of component atoms and correction factors. Altogether 90 atom types are used to classify carbon, nitrogen, oxygen, sulfur, phosphorus and halogen atoms, and 10 correction factors are used for some special substructures. The contributions of each atom type and correction factor are derived by multivariate regression analysis of 1853 organic compounds with known experimental log P values. The correlation coefficient (r) for fitting the whole set is 0.973 and the standard deviation (s) is 0.349 log units. Comparison of various log P calculation procedures demonstrates that our method gives much better results than other atom-additive approaches and is at least comparable to fragmental approaches. Because of the simple methodology, the `missing fragment' problem does not occur in our method.