Kinetics of the Triiodide Equilibrium

Abstract

The I¹²⁷ NMR absorption line of iodide ion in aqueous solution is broadened by the presence of iodine molecules. The broadening is consistent with the diminution of phase‐memory time caused by strong quadrupole coupling in triiodide ion, which occurs in dynamic equilibrium. On the basis of a simple bimolecular mechanism, the rate constants for the forward and reverse reactions of the triiodide equilibrium at ca 35°C are (4.1±0.4) × 10¹⁰ l/mole‐sec and (7.6±0.8) × 10⁷ sec^—1 in the concentration ranges which have been investigated.