Exploring the mechanism of diphenylmethanol oxidation: A combined experimental and theoretical approach

Abstract

The mechanistic aspects of hydroxyl (OH) and sulfate radical (SO4−) induced oxidation of diphenylmethanol (DPM) in aqueous medium has been explored using a combined experimental and theoretical approach. OH initiates the generation of hydroxycyclohexadienyl-type radicals (i) upon reaction with DPM (λmax = 330 nm; k2 = (1.44 ± 0.08) × 1010dm3 mol−1 s−1). Time-dependent density functional theory (TDDFT) calculations revealed an ortho-hydroxylated adduct structure to radical i,which shows comparable absorbance characteristics (λmax = 322 nm). High resolution mass spectrometric (HRMS) studies reveal the existence of mono- and di-hydroxylated compounds of DPM and benzophenone as the main degradation products. Hydroxylated products werederived from the radical i by either a radical-radical disproportion or a bimolecular transformation felicitated by molecular oxygen. Benzophenone (III) is likely originated from the radical cation (iii), generated as a result of one electron oxidation of DPM by OH/SO4−, by deprotonation followed by electron and proton release.