MECHANISM OF Fe-EDTA CATALYZED SUPEROXIDE DISMUTATION.

Article abstract of DOI:10.1021/ja00354a019

The catalysis of superoxide dismutation (2O//2 plus 2H** plus yields O//2 plus H//2O//2) by Fe**3** plus -EDTA and Fe**2** plus -EDTA has been examined. Potentiometric and spectrophotometric titrations of Fe**3** plus -EDTA revealed an ionization at pK//a equals 7. 6 consistent with the ionization of a bound water molecule. No other ionizations were detected below pH 10. 7. Potentiometric titration of Fe**2** plus -EDTA revealed no ionizations in the pH range 5-11. A mechanism has been derived for reaction 6 which accounts for the pH dependence of the individual rate constants, general-acid catalysis, and the pH dependence of the formation constant. The breakdown of the peroxo complex is catalyzed by both specific and general acids, and k// minus //6/ left bracket H** plus right bracket approximately equals 10**1**0 M** minus **1 s** minus **1 in the absence of general acids. The rate of formation of the peroxo complex is independent of pH but is increased by general acids.