Hydrogen atom abstraction by metal-oxo and metal-superoxo complexes: Kinetics and thermodynamics

Journal Article · Wed Feb 16 04:00:00 EST 2000 · Journal of the American Chemical Society

DOI:https://doi.org/10.1021/ja993371s· OSTI ID:20017358

Bakac, A

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

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ALKOXY RADICALS
CHROMIUM COMPLEXES
HYDROGEN
PEROXY RADICALS
RHODIUM HYDRIDES
SUPEROXIDE RADICALS
THERMODYNAMICS