PHOTOCHEMISTRY OF THE GASEOUS-HYDROGEN PEROXIDE CARBON-MONOXIDE SYSTEM .3. CALCULATED ENERGETICS FOR POSSIBLE HO2 CO COMPLEXES

At 298 K, HO2 radicals formed by secondary reactions in the photochemistry of the H2O2-CO system do not react with CO, whereas OH radicals formed in the primary process do. To explain the non-reactivity of HO2, we made Hartree-Fock calculations of the energies needed to form three probable HO2-CO intermediate radical complexes: I, HOOC=O; II, III. The values of Delta E for the reaction HO2+CO-->R and Delta H-f(o) for R obtained at 298 K are as follows: [GRAPHICS] From the high-temperature rate data, we conclude that the first stage of the reaction is the formation of complex I with Delta E the same or almost the same as the activation energy for the reaction to yield products CO2 and OH, and that every collision of the reactants with sufficient energy yields the complex.