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

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-.