Direct determination of the Gibbs' energy of formation of peroxynitrous acid
2003 (English)In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 42, no 12, 3796-3800 p.Article in journal (Refereed) Published
The kinetics of decomposition of peroxynitrous acid (ONOOH) was investigated in the presence of 0.1-0.75 M HClO4 and at a constant ionic strength. The decay rate of ONOOH decreased in the presence of H2O2, approaching a limiting value well below 75 mM H2O2. It also decreased in the presence of relatively low [HNO2] but did not approach a lower limiting value, since ONOOH reacts directly with HNO2. The latter reaction corresponds to a HNO2- and H+-catalyzed isomerization of ONOOH to nitrate, and its third-order rate constant was determined to be 520 +/- 30 M-2 s(-1). The mechanism of formation of O2NOOH from ONOOH in the presence of H2O2 was also scrutinized. The results demonstrated that in the presence of 0.1-0.75 M HClO4 and 75 mM H2O2 the formation Of O2NOOH is insignificant. The most important finding in this work is the reversibility of the reaction ONOOH + H2O reversible arrow HNO2 + H2O2, and its equilibrium constant was determined to be (7.5 +/- 0.4) x 10(-4) M. Using this value, the Gibbs' energy of formation of ONOOH was calculated to be 7.1 +/- 0.2 kcal/mol. This figure is in good agreement with the value determined previously from kinetic data using parameters for radicals formed during homolysis of peroxynitrite.
Place, publisher, year, edition, pages
2003. Vol. 42, no 12, 3796-3800 p.
tyrosine nitration, nitric-oxide, nitrous-acid, decomposition, radicals, kinetics, mechanism, decay
IdentifiersURN: urn:nbn:se:kth:diva-22573DOI: 10.1021/ic025698rISI: 000183410900015OAI: oai:DiVA.org:kth-22573DiVA: diva2:341271
QC 201005252010-08-102010-08-10Bibliographically approved