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Dalton Transactions

The international journal for inorganic, organometallic and bioinorganic chemistry



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Dalton Trans., 2009, 10541 - 10549, DOI: 10.1039/b906478h

Kinetics and mechanism of the Co(II)-assisted oxidation of L-ascorbic acid by dioxygen and nitrite in aqueous solution

Elena A. Vlasova, Natalya Hessenauer-Ilicheva, Denis S. Salnikov, Evgeny V. Kudrik, Sergei V. Makarov and Rudi van Eldik

A detailed study of the oxidation of L-ascorbic acid by dioxygen and nitrite in water at pH 5.8 and 7.0, catalyzed by the octasulfophenyltetrapyrazinoporphyrazine complex of cobalt(II), was carried out using conventional spectrophotometric, low-temperature and high-pressure stopped-flow techniques. The Co(II) complex activates L-ascorbic acid through an intramolecular one-electron oxidation step that involves the reduction of the octasulfophenyltetrapyrazinoporphyrazine. The reaction rate strongly depends on pH due to the different redox behaviour of the L-ascorbic acid/ascorbate species present in solution. Kinetic parameters for the different reaction steps of the catalytic process were determined. The final product of the reaction between L-ascorbic acid and nitrite was found to be nitrous oxide.

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