On the kinetics and mechanism of the oxidation of I− by OH/O− in alkaline aqueous solution

The kinetics and mechanism of the oxidation of I− to I2- by OH and O− in alkaline aqueous solution have been re-investigated by pulse radiolysis combined with optical detection. The data are shown to be consistent with k(OH + I− → HOI−) = 1.6 × 1010 and k[O− + I− (+H2O) → HOI− + OH−] = 2.0 × 109 dm3 mol−1 s−1, respectively, and the reversible dissociation of the adduct HOI− into I and OH− with kf(HOI−) = 3.5 × 107 s−1 and kr(I + OH−) = 1.6 × 108 dm3 mol−1 s−1 so that pKa(I · H2O) = 13.3. There is no evidence for the reactions HOI− → OH + I− and HOI-+I2-→I3-+OH-. The equilibrium HOI-+I-⇌I2-+OH- reported in the literature [H. Büchler, R.E. Bühler, Chem. Phys. 16 (1976) 9-18; H. Shiraishi, H. Okuda, Y. Morinaga, K. Ishigure, JAERI - M 92-012, 152-161.] in 10 mol dm−3 hydroxide solution is not detectable at pH 13.