Conversion of Pentahalogenated Phenols by Microperoxidase-8/H2O2 to Benzoquinone-Type Products

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• 作者：Ahmed M. Osman ; Maarten A. Posthumus ; Cees Veeger ; Peter J. van Bladeren ; Colja Laane ; and Ivonne M. C. M. Rietjens
• 刊名：Chemical Research in Toxicology
• 出版年：1998
• 出版时间：November 1998
• 年：1998
• 卷：11
• 期：11
• 页码：1319 - 1325
• 全文大小：246K
• 年卷期：v.11,no.11(November 1998)
• ISSN：1520-5010

文摘

This study reports the microperoxidase-8 (MP8)/H₂O₂-catalyzed dehalogenation of pentafluorophenol and pentachlorophenol, compounds whose toxic effects and persistence in theenvironment are well documented. The primary products of this dehalogenation reactionappear to be the corresponding tetrahalo-p-benzoquinones. Under the conditions used, thefluorinated phenol and its intermediate products are more susceptible to degradation thanthe corresponding chlorinated analogue and its products. The main degradation products oftetrachloro-p-benzoquinone and tetrafluoro-p-benzoquinone were identified as trichlorohydroxy-p-benzoquinone and trifluorohydroxy-p-benzoquinone, respectively. This secondary conversionof tetrafluoro-p-benzoquinone and tetrachloro-p-benzoquinone was not mediated by MP8, butwas driven by H₂O₂. Evidence is presented for a mechanism where H₂O₂ molecules and nothydroxide anions are the reactive nucleophilic species attacking the tetrahalo-p-benzoquinones.In addition to the formation of the trihalohydroxy-p-benzoquinones, the formation of adductsof the tetrahalo-p-benzoquinone products with ethanol, present in the incubation medium, wasobserved. The adduct from the reaction of tetrachloro-p-benzoquinone with ethanol was isolatedand identified as trichloroethoxyquinone. Thus, the present paper describes a system in whichthe formation of tetrahalo-p-benzoquinone-type products by an oxidative heme-based catalystcould be unequivocally demonstrated.