Hydrogen atom abstraction by metal-oxo and metal-superoxo complexes: Kinetics and thermodynamics
The superoxochromium complex Cr{sub aq}OO{sup 2+} abstracts a hydrogen atom from CMe{sub 3}CHO in acidic aqueous solution with k = 0.16 M{sup {minus}1} s{sup {minus}1}. This rate constant is only {approximately}10{sup 2} times smaller than that for the reaction of Cr{sub aq}O{sup 2+} with the same aldehyde, k = 23 M{sup {minus}1} s{sup {minus}1}, in contrast to the much greater reactivity difference between alkoxyl and alkylperoxyl radicals, k{sub t{minus}BuO}/k{sub t{minus}BuOO} {approximately}10{sup 6}. The absolute rate constants for hydrogen atom abstraction from a common reagent by metal-oxo and -superoxo species and the corresponding organic oxygen-centered radicals, RO{sup {sm{underscore}bullet}}, can now be compared for the first time: k{sub BuO} (9 x 10{sup 7} M{sup {minus}1} s{sup {minus}1}) > k{sub CrO}(23) {ge} k{sub BuOO}(8) > k{sub CrOO} (0.16). The reactivity of individual species is explained by the energetics of the O-H bonds in ROH, ROOH, Cr{sub aq}OH{sup 2+}, and Cr{sub aq}OOH{sup 2+}.
- Research Organization:
- Iowa State Univ., Ames, IA (US)
- Sponsoring Organization:
- US Department of Energy
- DOE Contract Number:
- W-7405-ENG-82
- OSTI ID:
- 20017358
- Journal Information:
- Journal of the American Chemical Society, Journal Name: Journal of the American Chemical Society Journal Issue: 6 Vol. 122; ISSN JACSAT; ISSN 0002-7863
- Country of Publication:
- United States
- Language:
- English
Similar Records
Reaction of hydrogen peroxide with the oxochromium(IV) ion by hydride transfer
Mechanism of oxidation of alkyl and superoxo complexes of chromium (III) by aquamanganese(III) ions