Aqueous phase kinetic studies involving intermediates of environmental interest: phosphate radicals and their reactions with substituted benzenes

Abstract

This manuscript describes our research work devoted to the understanding of the aqueous phase reactions of phosphate and polyphosphate radicals. Inorganic phosphate and polyphosphate radicals were generated after photolysis of peroxodiphosphate, tripolyphosphate and pyrophosphate ions. The reactions of SO₄ •⁻ radicals with P₂O₇ ⁴⁻ and P₃O₁₀ ⁵⁻ are also discussed. The logarithm of the bimolecular rate constants for the reactions of the three phosphate radicals (H₂PO₄ •, H₂PO₄ •⁻, PO4 •²⁻) with substituted benzenes are discussed in terms of Hammett correlations and a reaction mechanism is proposed. Phenoxyl type radical formation from the reactions of H₂PO₄ • and HPO₄ •⁻ radicals with phenol, chlorobenzene, and a, a, a-trifluorotoluene (TFT) supports the contribution of an addition pathway yielding a phosphate adduct with the substituted benzene. Additional information on the absorption spectra and decay kinetics of the hydroxycyclohexadienyl radicals of chlorobenzene and TFT is also given.