Reactions of phosphate radicals with monosubstituted benzenes. A mechanistic investigation

The kinetics and reaction mechanism of phosphate radicals with substituted benzenes, PhX (X = OH, Me, H, Cl, MeO, and CHO), were studied by flash photolysis and continuous irradiation of aqueous solutions containing potassium peroxodiphosphate (K-4[(PO3)(2)O-2]). The rate constants for the reactions of phosphate radicals with the aromatic contaminants PhX were measured and the reaction intermediates and products detected. A correlation between the logarithm of the rate constant for every substrate with H2PO4(.), HPO4.-, and PO4.2- and the logarithm of the dissociation constant K-a for H3PO4, H2PO4-, and HPO42- was found. A general mechanism is proposed (Scheme 1), which accounts for the experimental results.