Kinetics and mechanistic studies of chlorine dioxide reactions in aqueous solution, and, Kinetics of halites reactions with aqueous bromine chloride

Abstract

Chlorine dioxide is a strong oxidizing agent and a powerful disinfectant. The kinetics and mechanisms of several reactions involving chlorine dioxide in aqueous solution are determined. The self-decomposition of ClO2 is accelerated in the presence of hydroxide, carbonate, and phosphate. Three pathways are responsible for ClO2 decay, all of which are base-assisted electron-transfer reactions. The reaction of HO2− with ClO2 is fast (1.6 × 105 M −1s−1) and buffers do not affect the rate of the reaction. The relative rates of sulfur-containing species with ClO 2 are cysteine \u3e sulfite \u3e\u3e cystine. Aqueous Iron(II) reaction with ClO2 is rapid, a study of the subsequent Cl(III)/Fe2+ reaction is completed and an overall mechanism for the five-electron reduction of ClO2 to Cl− is outlined. Bromine chloride is involved in ozone depletion in the troposphere during the polar sunrise in the Arctic. Aqueous bromine chloride reacts with halites through BrOXO intermediates (X = Br or Cl). The reaction of ClO2 − with BrCl to give ClO2 is 27.4 times faster the BrCl/BrO2 reaction. The BrCl/BrO2 reaction forms chloride and the carcinogen bromate. Both reactions proceed by Br+-transfer mechanisms