Contribution of Substituents to the Distribution Coefficient of N-Benzoyl-N-phenylhydroxylamine Derivatives

Abstract

The distribution coefficient (K_d) for twenty kinds of N-benzoyl-N-phenylhydroxylamine (BPHA) derivatives between chloroform or benzene and the aqueous phase was determined. A linear correlation was obtained between log K_d and the number of carbon atoms containing substituent groups for a series of alkyloxy derivatives. However, the data for those having a series of alkyloxy groups, and others having a straight or branched alkyl chain, fall on two independent lines in plots of log K_Dvs. the van der Waals volume of the BPHA derivatives. From these results, the empirical contribution values (π_x), defined as π_x=log K_D(X)—log K_D(H) K_D(H) is the distribution coefficient of a parent compound and K_D(X) that of a derivative}, of the functional group to the distribution coefficient (log K_D), were as follows: 0.54 in a chloroform/ water system and 0.49 in a benzene/ water system for the methyl and methylene groups, 0.30 in a chloroform/water system and 0.27 in a benzene/water system for the methoxy group, and —0.23 in a chloroform/water system and —0.12 in a benzene/water system for the nitro group, respectively. The utility of the contribution values π_x) for the methyl, methylene, methoxy and nitro groups was verified for estimating the distribution coefficient (K_D) of the BPHA derivatives.