Aqueous solubility and n-octanol/water partition coefficient correlations

Abstract Studies of the fate of chemicals require the knowledge of numerous parameters, among which of utmost importance are the water solubility and the n-octanol/water partition coefficient. Numerous writers have demonstrated that there is a close correlation between these two parameters. The literature offers about fifteen cases of correlations between solubility and n-octanol/water partition coefficient with, for some of them, and for solids, a third variable: the fusion point. Unfortunately, the coefficients are often the results of theoretical considerations and the size of the data base is often small. A study carried out on 300 products shows clearly the importance of the size of the data base. It is demonstrated that the coefficients obtained in practice are different from those which had been calculated theoretically. In particular, the introduction of a fusion point correction appears to be justified only to a limited extent. This analysis has shown that there is a need to reexamine the theoretical approach and determine why the coefficients of the regression equation do not appear to adopt the values excepted from theoretical considerations.