Kinetics and Mechanism of the Oxidation of Iodine by Chlorite Ion

John L. Grant, Patrick De Kepper, Irving R. Epstein, Kenneth Kustin, Miklós Orbán

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16 Citations (Scopus)

Abstract

The stoichiometry of the reaction between chlorite and iodine in the pH range 2–5 and at low [I] has been determined to be 5C102 + 2I2 + 2H2O − 5C1 + 4IO3 + 4H+. The kinetics of this reaction have been studied by stopped-flow spectrophotometry at 22.2 °C and variable ionic strength (10−2−10−1 M). The rate law is −½d[I2]/dt = (k1/[ClO2] +/k2[C1O2]/[H+] + k3)[I2], where k1 = (1.1 ± 0.4) × 10 M−1 s−1, k2 = (1.1 ± 0.1) × 10−2 s−1, and k3 = (5.4 ± 0.3) × 10−1 s−1. A mechanism is proposed involving formation of the key intermediate IC1O2 by reactions between chlorite and I2, I2OH, and IOH2+. The rate constant for the elementary reaction C1O2 + I2 → IC1O2 + I is given by k1. The value of the rate constant for the elementary reaction I2OH + ClO2 - IClO2 + I + OH is 7.7 × 107 M−1 s−1. We have identified k3 with the reaction I2 + H2O → IOH2+ + I.

Original languageEnglish
Pages (from-to)2192-2196
Number of pages5
JournalInorganic Chemistry
Volume21
Issue number6
DOIs
Publication statusPublished - 1982

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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