Kinetics and Mechanism of the Autocatalytic Reaction between Iodine and Chlorite Ion

The kinetics of oxidation of iodine by chlorite is much more complicated than previously found. The rate exhibits a minimum as a function of hydrogen ion concentration, the reaction being characteristically autocatalytic, mainly due to the fact that oxidation of iodine is even faster by hypochlorous acid and chlorine. An important feature of the reaction is the acceleration of the disproportionation of chlorite by the intermediates of the title reaction, leading to the formation of a significant amount of chlorine dioxide. The rate cannot be described by an overall equation, but all the findings can be quantitatively explained by a mechanism consisting of 13 elementary or quasi-elementary steps. The stoichiometry of the reaction is kinetically controlled. Formation and reactions of Cl₂O₂seem to play a crucial role in the reaction and in other reactions involving chlorite.