Altaf, Mohammad.Jaganyi, Deogratius.2024-06-282024-06-282013-10-23Mohammad Altaf & Deogratius Jaganyi. (2016) Oxidative degradation of l -histidine by manganese dioxide (MnO 2 ) nano-colloid in HClO 4 medium with/without using TX-100 catalyst: a kinetic approach . RSC Advances 6:103, pages 101162-101170.https://doi.org/10.1080/01932691.2012.751029https://erepository.mku.ac.ke/handle/123456789/5951The oxidation of methionine by freshly prepared colloidal manganese dioxide in aqueous as well as micellar media was studied spectrophotometrically at 35°C. The reaction between methionine and MnO2 in both media exhibits 1:1 stoichiometry (methionine:MnO2). The oxidation reaction is first order with regard to the MnO2 concentration, but is fractional-order in the methionine concentration and HClO4 concentrations. A catalytic effect of nonionic surfactant TX-100 on the rate of oxidation was observed and reaction rate was found to be proportional to {k′ + k″ [TX-100]}, where k′ and k″ are the rate constants in absence and presence of surfactant, respectively. The use of surfactant micelles is highlighted as, in favorable cases; the micelles help the redox reactions by bringing the reactants in a close proximity through hydrogen bonding. The oxidation reaction in aqueous and micellar media is shown to proceed via methionine–MnO2 and methionine–MnO2–TX-100 complexes, respectively, which decomposes slowly in a rate determining step to give methionine sulfoxide as the product. A suitable mechanism is proposed for these observations.enArticle