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Vol. 27 No. 10 (2015): Vol 27 Issue 10

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Mechanism of Oxidation of L-Cysteine by Tetraoxoiodate(VII) in Aqueous Acid Medium

https://doi.org/10.14233/ajchem.2015.18976
Pius O. Ukoha
Department of Pure and Industrial Chemistry, University of Nigeria, Nsukka, Enugu State, Nigeria
Oguejiofo T. Ujam
Department of Pure and Industrial Chemistry, University of Nigeria, Nsukka, Enugu State, Nigeria; Department of Chemistry, University of Victoria, Victoria, BC, V8W 3V6, Canada
Johnson F. Iyun
Department of Chemistry, Ahmadu Bello University, Zaria, Kaduna State, Nigeria
Solomon E.O. Okereke
Department of Pure and Industrial Chemistry, Abia State University, Uturu, Abia State, Nigeria

Corresponding Author(s) : Oguejiofo T. Ujam

oguejiofo.ujam@unn.edu.ng

Asian Journal of Chemistry, Vol. 27 No. 10 (2015): Vol 27 Issue 10

Abstract

The kinetics and mechanism of the oxidation of L-cysteine by tetraoxoiodate(VII) ion in aqueous acid medium has been studied at 0.03 £ [H+] £ 0.1 mol dm-3 under pseudo-first order conditions of an excess of tetraoxoiodate(VII) concentration at 1 = 0.11 mol dm-3 (NaClO4). The reaction obeys the rate expression:


-d [IO4–]/dt = {k3K1K2[H+] + k5} [RSH][IO4–]


Addition of AcO– and NO3– had no effect on the reaction but the rate of reaction decreased with increase in ionic strength of the medium. Increase in dielectric constant decreased the rate of reaction. The rates are consistent with a mechanism which involves the formation of free radicals which subsequently dimerized into disulfides. The reaction has been rationalized on the basis of the inner-sphere electron transfer mechanism.

Keywords

L-Cysteine Oxidation Mechanism Tetraoxoiodate(VII)
O. Ukoha, P., T. Ujam, O., F. Iyun, J., & E.O. Okereke, S. (2015). Mechanism of Oxidation of L-Cysteine by Tetraoxoiodate(VII) in Aqueous Acid Medium. Asian Journal of Chemistry, 27(10), 3777–3780. https://doi.org/10.14233/ajchem.2015.18976
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