Reaction of peroxynitrite with carbon dioxide: intermediates and determination of the yield of CO3*- and NO2*.
CO2 catalyses the isomerization of the biological toxin ONOO- to NO3- via an intermediate, presumably ONOOCO2-, which has an absorption maximum near 650 nm. The reflection spectrum of solid NMe4+ ONOO- exposed to CO2 shows a similar band near 650 nm; this absorption decays over minutes. Stopped-flow experiments in which CO2 solutions were mixed with alkaline ONOO- solutions indicate the formation of at least one intermediate. The initial absorption at 302 nm is less than that of ONOO-, which indicates that reactions take place within the mixing time, and this absorption is dependent (but not linearly) on the ONOO- and CO2 concentrations. We found that reaction of peroxynitrite with carbon dioxide forms some trioxocarbonate(*1-) (CO3*-) and nitrogen dioxide (NO2*) radicals via homolysis of the O-O bond in ONOOCO2-. We determined the extent of radical formation by mixing peroxynitrite, carbon dioxide and nitrogen monoxide. The later reacts with CO3*- and NO2* radicals to form, effectively, three NO2- per homolysis; ONOOCO2- that does not undergo homolysis yields NO3- and CO2. Based on the NO3- and NO2- analyses, the extent of conversion to NO3- is 96 +/- 1% and that of homolysis is 3 +/- 1%, respectively, significantly less than that reported in the literature.
Meli
Roger
R
Laboratorium für Anorganische Chemie, Eidgenössische Technische Hochschule, Universitätsstrasse 6, 8092 Zurich, Switzerland.
Nauser
Thomas
T
Latal
Petr
P
Koppenol
Willem H
WH
D002245:Carbon Dioxide / Q000737:chemistry*; D002254:Carbonates / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D005609:Free Radicals / Q000737:chemistry; D007536:Isomerism; D007700:Kinetics; D009573:Nitrites / Q000737:chemistry*; D030421:Peroxynitrous Acid / Q000737:chemistry*; D013057:Spectrum Analysis / Q000379:methods
D002254:Carbonates; D005609:Free Radicals; D009573:Nitrites; D002245:Carbon Dioxide; D030421:Peroxynitrous Acid