Kinetics and mechanisms of the non-metal redox reactions of chlorite and bromite ions

Jeffrey S Nicoson, Purdue University

Abstract

The mechanisms of several non-metal redox reactions of chlorite and bromite ions are determined. The reaction of Cl2 with ClO2 − occurs by Cl+-transfer to form ClOClO in the rate-determining step. Rapid reactions of ClOClO with ClO2 − and H2O form ClO2 and ClO3 −, respectively, and release Cl−. The reactions of HOCl, Cl2O, Cl2, HOBr, Br2O, and Br 2 with BrO2− also occur through halogen-cation transfer mechanisms. In the reactions of HOCl and Cl2O with BrO 2−, the formation of steady-state species, HOClOBrO − and ClOClOBrO−, is followed by an interconversion to HOBrOClO−. The HOBrOClO− intermediate dissociates into HOBr and ClO2− or undergoes acid-assisted decomposition to form BrOClO. The BrOClO intermediate rapidly hydrolyzes to form ClO3− and Br− as the major products. The reaction of BrOClO with ClO2 − forms 2ClO2 and Br− in a minor pathway. The metastable BrOClO intermediate exists as a cyclic adduct with HOCl. In the reactions of HOBr and Br2O with BrO2 −, the formation of the steady-state species, HOBrOBrO − and BrOBrOBrO−, is followed by their acid-assisted decomposition to form BrOBrO. The rapid hydrolysis of BrOBrO forms BrO3− and Br− as the final products. The reactions of Cl2 and Br2 with BrO2− form the steady-state species, ClOBrO and BrOBrO, respectively. The hydrolysis of ClOBrO and BrOBrO forms BrO 3− and Cl− or Br− as the final products. The reaction of O3 with BrO 2− occurs through an initial electron-transfer step to form O3− and BrO2. The O3− radical rapidly decays to OH radical and O2. The reaction of OH radical with BrO2− produces BrO2 and OH−. The BrO 2 intermediate is produced in observable concentrations prior to its disproportionation into BrO2− and BrO 3−.

Degree

Ph.D.

Advisors

Margerum, Purdue University.

Subject Area

Analytical chemistry

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