Identification of Intermediate and Product from Methemoglobin-Catalyzed Oxidation of o-Phenylenediamine in Two-Phase Aqueous-Organic System

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De-Jia Li, Xi-Wen Li, Yu-Xiang Xie, Xiao-Qiang Cai, and Guo-Lin Zou^*

College of Life Sciences, Wuhan University, Wuhan, Hubei 430072, PR China; fax: +86-27-87669560; E-mail: zouguolin@whu.edu.cn

^* To whom correspondence should be addressed.

Received April 21, 2004; Revision received June 1, 2004

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Methemoglobin (metHb) was used as a mimetic enzyme for peroxidase to catalyze the oxidation reaction of o-phenylenediamine (OPDA) with H₂O₂ functioning as an oxidant. A reaction intermediate was obtained in two-phase aqueous-organic system and an absorption peak at 710 nm was confirmed to be that of the intermediate in relation to OPDA. The isolated product and intermediate were characterized by UV-Vis and IR spectrophotometry and HPLC-tandem mass spectrometry. The results showed that the product is 2,3-diaminophenazine, the molecular mass of the intermediate is 212 daltons, and a conceivable structure of the intermediate is suggested. Combining the catalyzed reaction mechanism of peroxidase and our experimental results, a conceivable oxidation reaction mechanism of OPDA and H₂O₂ using metHb as catalyst is proposed.

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KEY WORDS: hemoglobin, o-phenylenediamine, intermediate, reaction mechanism

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