Enzymatic degradation of 2,6-dichlorophenol by horseradish peroxidase: UV–visible and mass spectrophotometric characterization of the reaction products

Abstract The reaction mechanism of the oxidation of 2,6-dichlorophenol (2,6-DCP) by horseradish peroxidase (HRP) and H 2 O 2 has been investigated and the reaction products have been characterized by UV–visible and mass spectrometry. Evidence for the dimerization of 2,6-DCP to 3,3′,5,5′-tetrachloro-4,4′-dihydroxybiphenyl and the subsequent fast oxidation of this product to the corresponding 3,3′,5,5′-tetrachlorodiphenoquinone have been collected. The reaction rate was found to decrease markedly as soon as the pH was raised, with a clear inflection point at pH≅6.6–6.9; it also resulted independent from H 2 O 2 concentration. Since the p K a for 2,6-DCP is 6.80, the reaction rate might be influenced by the protonation state of the substrate.