Mechanism of decomposition of peroxynitric ion (O2NOO-):: Evidence for the formation of O2•- and •NO2 radicals

The rate constant of the self-decomposition of O2NOO- was determined to be 1.35 +/- 0.03 s(-1) at 25 degrees C. The decomposition rate constant of O2NOO- in the presence of C(NO2)(4), CuSO4, SOD, and Fe(CN)(6)(4-) was found to be 2.4 +/- 0.2 s(-1), independent of the concentration of these substrates. The oxidation yields of C(NO2)(3)(-) and ferricyanide were measured to be 47 +/- 5 and 83 +/- 9% of added peroxynitrate, respectively, where the latter decreased to 54 +/- 6% in the presence of SOD. We therefore suggest that ca. 50% of O2NOO- homolyses into O-2(.-) and . NO2 (k = 1.05 +/- 0.23 s(-1)). The equilibrium constant of the homolysis of O2NOO- into . NO2 and O-2(.-) and the reduction potential of the couple O2NOOH,H+/NO3- were calculated to be 2.3 x 10(-10) M and 1.83 V, respectively.