Mechanisms of the Reactions of Radicals with Ozone

Abstract

The available experimental data (rate constants and activation energies) for the reactions of the hydrogen atom and the R•, RO•, RO2•, HO•, and HO2• radicals with ozone are analyzed using the method of intersecting parabolas (potential curves). The conclusion is drawn that the primary event in the reactions of H•, R•, HO•, and RO• with ozone is the addition of the radical to the ozone molecule with the subsequent fast decomposition of the labile polyoxide radical formed. The classical potential barrier for this addition reaction is close to that for the addition of radicals to molecules with multiple bonds. Peroxy radicals react with ozone by the associative decomposition mechanism, RO2• + O3 → RO• + 2O2. The ozone molecule reacts with the HO2• radical by abstracting its hydrogen atom, O3 + HO2• → HO3• + O2. The experimental data were used to determine the parameters required to calculate the activation energies for the reactions under study.