MECHANISM OF DECOMPOSITION OF PEROXYNITRIC ION (O2NOO-) - EVIDENCE FOR THE FORMATION OF O-2(CENTER-DOT-) AND (NO2)-N-CENTER-DOT RADICALS

The rate constant of the self-decomposition of O2NOO- was determined t o be 1.35 +/- 0.03 s(-1) at 25 degrees C. The decomposition rate const ant 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 concentratio n of these substrates. The oxidation yields of C(NO2)(3)(-) and ferric yanide were measured to be 47 +/- 5 and 83 +/- 9% of added peroxynitra te, respectively, where the latter decreased to 54 +/- 6% in the prese nce 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 p otential of the couple O2NOOH,H+/NO3- were calculated to be 2.3 x 10(- 10) M and 1.83 V, respectively.