Kinetics and Mechanisms of the Reactions of Hypochlorous Acid, Chlorine, and Chlorine Monoxide with Bromite Ion

The reaction between BrO2- and excess HOCl (p[H+] 6−7, 25.0 °C) proceeds through several pathways. The primary path is a multistep oxidation of HOCl by BrO2- to form ClO3- and HOBr (85% of the initial 0.15 mM BrO2-). Another pathway produces ClO2 and HOBr (8%), and a third pathway produces BrO3- and Cl- (7%). With excess HOCl concentrations, Cl2O also is a reactive species. In the proposed mechanism, HOCl and Cl2O react with BrO2- to form steady-state species, HOClOBrO- and ClOClOBrO-. Acid facilitates the conversion of HOClOBrO- and ClOClOBrO- to HOBrOClO-. These reactions require a chainlike connectivity of the intermediates with alternating halogen−oxygen bonding (i.e. HOBrOClO-) as opposed to Y-shaped intermediates with a direct halogen−halogen bond (i.e. HOBrCl(O)O-). The HOBrOClO- species dissociates into HOBr and ClO2- or reacts with general acids to form BrOClO. The distribution of products suggests that BrOClO exists as a BrOClO·HOCl adduct in the presence of excess HOCl. The primary products, Cl...