Disproportionation pathways of aqueous hyponitrite radicals (HN2O2(*)/N2O2(*-))

The Journal of Physical Chemistry. a
Gregory A PoskrebyshevSergei V Lymar

Abstract

Pulse radiolysis and flash photolysis are used to generate the hyponitrite radicals (HN2O2(*)/N2O2(*-)) by one-electron oxidation of the hyponitrite in aqueous solution. Although the radical decay conforms to simple second-order kinetics, its mechanism is complex, comprising a short chain of NO release-consumption steps. In the first, rate-determining step, two N2O2(*-) radicals disproportionate with the rate constant 2k = (8.2 +/- 0.5) x 10(7) M(-1) s(-1) (at zero ionic strength) effectively in a redox reaction regenerating N2O2(2-) and releasing two NO. This occurs either by electron transfer or, more likely, through radical recombination-dissociation. Each NO so-produced rapidly adds to another N2O2(*-), yielding the N3O3(-) ion, which slowly decomposes at 300 s(-1) to the final N2O + NO2(-) products. The N2O2(*-) radical protonates with pKa = 5.6 +/- 0.3. The neutral HN2O2(*) radical decays by an analogous mechanism but much more rapidly with the apparent second-order rate constant 2k = (1.1 +/- 0.1) x 10(9) M(-1) s(-1). The N2O2(*-) radical shows surprisingly low reactivity toward O2 and O2(*-), with the corresponding rate constants below 1 x 10(6) and 5 x 10(7) M(-1) s(-1). The previously reported rapid dissociation of N2...Continue Reading

References

Jan 19, 2002·The Journal of Biological Chemistry·Michael Kirsch, Herbert de Groot
May 29, 2002·Proceedings of the National Academy of Sciences of the United States of America·Vladimir Shafirovich, Sergei V Lymar
Jun 6, 2003·Journal of the American Chemical Society·Vladimir Shafirovich, Sergei V Lymar
Jan 22, 2004·Journal of the American Chemical Society·Gregory A PoskrebyshevSergei V Lymar
Jun 9, 2005·Chemical Reviews·Sara GoldsteinGábor Merényi
Jul 19, 2005·Inorganic Chemistry·Sergei V LymarGregory A Poskrebyshev
May 10, 2007·The Journal of Physical Chemistry. B·Sergei V Lymar, Vladimir Shafirovich

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Citations

Sep 4, 2009·Archives of Pharmacal Research·Wilmarie Flores-SantanaDavid A Wink
Jan 18, 2011·Antioxidants & Redox Signaling·Wilmarie Flores-SantanaDavid A Wink
Nov 6, 2012·Journal of Inorganic Biochemistry·Yuval SamuniSara Goldstein
Oct 30, 2012·Journal of Inorganic Biochemistry·Maksim RoyzenStephen J Lippard
Sep 10, 2014·Journal of Inorganic Biochemistry·Nizamuddin ShaikhSergei V Lymar
May 20, 2015·Journal of the American Chemical Society·Carl K BrozekMircea Dincă
May 28, 2010·Journal of the American Chemical Society·Uri SamuniSara Goldstein
Nov 7, 2019·Inorganic Chemistry·Juan P MarcolongoJosé A Olabe
Jul 7, 2009·Free Radical Biology & Medicine·Matthew I JacksonJon M Fukuto

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