Kinetics and mechanism of the oxidation of iodine by chlorite ion

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

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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 5ClO2- + 2I2 + 2H2O → 5Cl- + 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 -1/2d[I2]/dt = (k1[ClO2-] + k2[ClO2-]/[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 IClO2 by reactions between chlorite and I2, I2OH-, and IOH2+. The rate constant for the elementary reaction ClO2- + I2 → IClO2 + 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
Publication statusPublished - 1982

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Iodine
iodine
Rate constants
Ions
Oxidation
oxidation
Kinetics
Spectrophotometry
kinetics
Ionic strength
Stoichiometry
ions
spectrophotometry
chlorite
stoichiometry
hydroxide ion

ASJC Scopus subject areas

  • Inorganic Chemistry

Cite this

Grant, J. L., De Kepper, P., Epstein, I. R., Kustin, K., & Orbán, M. (1982). Kinetics and mechanism of the oxidation of iodine by chlorite ion. Inorganic Chemistry, 21(6), 2192-2196.

Kinetics and mechanism of the oxidation of iodine by chlorite ion. / Grant, John L.; De Kepper, Patrick; Epstein, Irving R.; Kustin, Kenneth; Orbán, M.

In: Inorganic Chemistry, Vol. 21, No. 6, 1982, p. 2192-2196.

Research output: Contribution to journalArticle

Grant, JL, De Kepper, P, Epstein, IR, Kustin, K & Orbán, M 1982, 'Kinetics and mechanism of the oxidation of iodine by chlorite ion', Inorganic Chemistry, vol. 21, no. 6, pp. 2192-2196.
Grant JL, De Kepper P, Epstein IR, Kustin K, Orbán M. Kinetics and mechanism of the oxidation of iodine by chlorite ion. Inorganic Chemistry. 1982;21(6):2192-2196.
Grant, John L. ; De Kepper, Patrick ; Epstein, Irving R. ; Kustin, Kenneth ; Orbán, M. / Kinetics and mechanism of the oxidation of iodine by chlorite ion. In: Inorganic Chemistry. 1982 ; Vol. 21, No. 6. pp. 2192-2196.
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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 5ClO2- + 2I2 + 2H2O → 5Cl- + 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 -1/2d[I2]/dt = (k1[ClO2-] + k2[ClO2-]/[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 IClO2 by reactions between chlorite and I2, I2OH-, and IOH2+. The rate constant for the elementary reaction ClO2- + I2 → IClO2 + 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-.",
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N2 - The stoichiometry of the reaction between chlorite and iodine in the pH range 2-5 and at low [I-] has been determined to be 5ClO2- + 2I2 + 2H2O → 5Cl- + 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 -1/2d[I2]/dt = (k1[ClO2-] + k2[ClO2-]/[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 IClO2 by reactions between chlorite and I2, I2OH-, and IOH2+. The rate constant for the elementary reaction ClO2- + I2 → IClO2 + 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-.

AB - The stoichiometry of the reaction between chlorite and iodine in the pH range 2-5 and at low [I-] has been determined to be 5ClO2- + 2I2 + 2H2O → 5Cl- + 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 -1/2d[I2]/dt = (k1[ClO2-] + k2[ClO2-]/[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 IClO2 by reactions between chlorite and I2, I2OH-, and IOH2+. The rate constant for the elementary reaction ClO2- + I2 → IClO2 + 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-.

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