A non-linear function for the approximation of octanol/water partition coefficients of aromatic compounds with multiple chlorine substitution

Abstract

From the comparison of linear and power curve regression analyses of several sets of congeners, it is suggested that the increasing chlorine substitution of aromatic and heterocyclic parent compounds, such as benzene, aniline, pyridine, and diphenyl results in declining increases of the octanol/water partition coefficients. The partition coefficients of the chloro congeners follow the general equation logP N = (N +1)∗ logP O , where N is the number of chlorine substituents, logP O the partition coefficient of the parent compound and b is a constant, specific for each set of congeners. The parameters logP O and b are also correlated with each other by the equation b = z∗ logP O Y , where z and y are the same constants for all sets. Together, the two equations allow the quick estimation of the partition coefficient of any congener from the known value of another. This ability is of special importance for compounds with 4 < logP, where experimental values are difficult to obtain.