Pulse radiolytic investigation of O_aq^- radical ions

The reactivity of the oxidizing radicals in N₂O saturated aqueous solutions was measured by pulse radiolysis. Competition experiments between methanol, ethanol, and other solutes such as ferrocyanide, iodide, bromide, thiocyanate, ferrous, and cerous ions were carried out. Comparison with results in the alkaline pH range indicates that O^- is formed as an intermediate in the reaction of e_aq^- with N₂O. O^- reacts quickly with water, k_(o-+H2o) = 9.6 × 10⁷ sec^-1. At high solute concentrations, competition for O^- (generated from N₂O) was carried out. The following reaction rate constants (in M^-1 sec^-1) were determined: k_(o-+I-) = 2.2 × 10⁹; k_(o-+CNS-) = 1.4 × 10⁹; k_{(O-+methanol)} = 5.3 × 10⁸; k_(O-+ethanol) = 9.8 × 10⁸; k_{(O-+ferrocyanide)} ≤ 3 × 10⁷; k_(o-+Br-) = 1.8 × 10⁸; k_(o-+ferrous) = 3.1 × 10⁹; k_(O-+cerous) = 5.9 × 10⁸. The reactivity of O^- as compared with that of OH is discussed. An upper limit (∼10⁷ sec^-1) is estimated for k_{(N2O-→N2+o-)}.