Kinetics and mechanism of catalytic decomposition and oxidation of chlorine dioxide by the hypochlorite ion

The oxidation of ClO2 by OCl- is first order with respect to both reactants in the neutral to alkaline pH range: -d[ClO2]/dt = 2k(OCl)[ClO2][OCl-]. Th e rate constant (T = 298 K, mu = 1.0 M NaClO4) and activation parameters ar e k(OCl) = 0.91 +/- 0.02 M-1 s(-1), DeltaH(double dagger) = 66.5 +/- 0.9 kJ /mol, and DeltaS(double dagger) = -22.3 +/- 2.9 J/(mol K). In alkaline solu tion, pH > 9, the primary products of the reaction are the chlorite and chl orate ions and consumption of the hypochlorite ion is not observed. The hyp ochlorite ion is consumed in increasing amounts, and the production of the chlorite ion ceases when the pH is decreased. The stoichiometry is kinetica lly controlled, and the reactants/products ratios are determined by the rel ative rates of the production and consumption of the chlorite ion in the Cl O2/OCl- and HOCl/ClO2- reactions, respectively.