Abstract

A Quantitative Structure-Activity Relationship (QSAR) was developed for the photohydrolysis of meta-substituted halogenated benzene derivatives in water. At low concentrations both the starting compounds and the photoproducts were irradiated at wavelengths ranging from 250 - 350 nm. By measuring the concentration of the starting compounds and the photoproducts as a function of time, first order rate constants for direct photolysis were determined. Subsequently, quantum yields for photohydrolysis were determined. To this end use was made of the measured rates of disappearance, the relative energy distribution of the light source used and the UV-spectra of the starting compounds. Calculated quantum yields were 10log-transformed and correlated to a limited number of structural parameters. The best correlation was obtained using the inductive constants and the summation of the steric constants of the substituents to the benzene moiety as parameters.