NONMETAL REDOX KINETICS - A REEXAMINATION OF THE MECHANISM OF THE REACTION BETWEEN HYPOCHLORITE AND NITRITE IONS

Hypochlorite oxidation of NO2- does not take place by oxygen atom transfer, but proceeds by Cl+ transfer from HOCl to NO2- to give NO2Cl as a reaction intermediate. The kinetics indicate that the subsequent decomposition of NO2Cl proceeds by two pathways: loss of Cl- to give NO2+ and reaction of NO2Cl with NO2- to form N2O4 and Cl-. At high Cl- and low OH- and NO2- concentrations the overall rate of NO3- formation is suppressed by Cl-. The relative reactivities for the reaction with NO2+ are OH- >> Cl- >> H2O. Although oxygen isotope experiments are consistent with a Cl+ transfer mechanism, the rate of exchange of oxygen between OCl- and H2O is relatively rapid (even at high pH in the absence of Cl-). We predict that the OCl-/H2O exchange rate in base will be independent of OH- concentration.