title: Kinetics and Mechanism of Oxidation of Methimazole by Chlorite in Slightly Acidic Media.
abstract: The kinetics and mechanism of the oxidation of methimazole (1-methyl-3H-imidazole), MMI, by chlorite in mildly acidic environments were studied. It is a complex reaction that gives oligo-oscillations in chlorine dioxide concentrations in excess chlorite conditions. The stoichiometry is strictly 2:1, with the sulfur center being oxidized to sulfate and the organic moiety being hydrolyzed to several indeterminate species. In excess MMI conditions over chlorite, the sulfinic acid and sulfonic acid were observed as major intermediates. The sulfenic acid, which was observed in the electrochemical oxidation of MMI, was not observed with chlorite oxidations. Initial reduction of chlorite produced HOCl, an autocatalytic species in chlorite oxidations. HOCl rapidly reacts with chlorite to produce chlorine dioxide, which, in turn, reacts rapidly with MMI to produce more chlorite. The reaction of chlorine dioxide with MMI is competitive, in rate, with the chlorite-MMI and HOCl-ClO2(-) reactions. This explains the oligo-oscillations in ClO2 concentrations.
authors.affiliation: Department of Chemistry, Portland State University , Portland, Oregon 97207-0751, United States.
authors.forename: Kudzanai
authors.initials: K
authors.lastname: Chipiso
authors.affiliation: Department of Chemistry, Portland State University , Portland, Oregon 97207-0751, United States.|School of Chemistry and Physics, University of KwaZulu-Natal , Westville Campus, Durban 4014, South Africa.
authors.forename: Reuben H
authors.initials: RH
authors.lastname: Simoyi
mesh_terms: D002712:Chlorides / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008713:Methimazole / Q000737:chemistry*; D016877:Oxidants / Q000737:chemistry; D010084:Oxidation-Reduction
chemical_list: D002712:Chlorides; D016877:Oxidants; D008713:Methimazole; C001599:chlorite