Development of the fragment constant method for estimating the partition coefficients of nonionic organic mixtures.

The fragment constant model for estimating partition coefficient of nonionic organic mixtures is developed based on group contribution theory. For 60 mixtures randomly composed of eight substituted benzenes, the C(18)-Empore disks/water partition coefficients (K(MD)) are determined. Establishment of a model between these K(MD) and the mole fraction of the fragments (Cl, Br, I, NO(2), CH(3)) acquires the fragments constants for K(MD). The significant linear regression equation, between these fragment constants and that of Hansch, provides an approach for calculating K(MD) of untested nonionic organic mixtures by using the fragment constants of Hansch.