Oxidation of Peroxynitrite by Inorganic Radicals: A Pulse Radiolysis Study

Abstract

Reactivity of the peroxynitrite ion toward a number of inorganic radicals was determined by using the pulse radiolysis technique. The rate constants for the oxidation of the ONOO- ion by CO3•-, •N3, and ClO2• radicals were determined from their decay kinetics to be (7.7 ± 1.2) × 106 (I = 0.6 M), (7.2 ± 0.9) × 108, and (3.2 ± 0.3) × 104 M-1 s-1, respectively. For the •OH radical, the rate constant of (4.8 ± 0.8) × 109 M-1 s-1 was obtained by using competition kinetic analysis. The oxidation potential of the ONOO- ion was estimated as 0.8 V from the kinetic data. Although thermodynamically favorable, oxidation of ONOO- by the •NO2 radical was not observed; an upper limit of 2.5 × 104 M-1 s-1 could be set for this reaction. Contribution from some of these reactions to the decomposition of peroxynitrite in the presence and absence of CO2 is discussed.