Disproportionation of chlorous acid. I. Stoichiometry

Article abstract of DOI:10.1021/ic50060a013

The disproportionation of chlorous acid was studied at an ionic strength of 2.0 M under a variety of hydrogen ion conditions from 1.2 × 10^-3 to 2.0 M and with up to 0.1 M added chloride ion. In the absence of added chloride ion, in 1.2 and 2.0 M perchloric acid at 25°, the stoichiometry can be approximated as: 4HClO₂ → 2ClO₂ + ClO₃^- + Cl^- + 2H⁺ + H₂O. At the beginning of the reaction less chlorine dioxide than that predicted by the above equation is formed, and, as the reaction proceeds, the relative amount of chlorine dioxide produced increases. The relative amount of chlorine dioxide produced also varies with the hydrogen ion concentration. Chloride ion catalyzes the disproportionation of chlorous acid and also alters the stoichiometry to approximately 5HClO₂ → 4ClO₂ + Cl^- + H⁺ + 2H₂O. As the reaction proceeds in the presence of initial chloride ion, less chlorine dioxide than that predicted by the second equation is formed. Also, as the initial concentration of chloride ion is decreased, the relative amount of chlorine dioxide formed decreases. A mechanism which is consistent with these observations is proposed.