The Reaction of O(3P) with C2Cl4

Abstract

The reaction of O(3P), prepared from Hg photosensitization of N2O with C2Cl4 was studied at 25 °C. The exclusive products of the reaction in the absence of O2 were CCl2O and polymer (as well as N2 from the N2O). The quantum yield of CCl2O production, Φ{CCl2O}, was 0.19 independent of the C2Cl4 pressure or the absorbed intensity, Ia. There was no evidence for CO, Cl2, c-C3Cl6, CCl3CCl(O), or [Formula: see text] production. The reaction mechanism is[Formula: see text]with k12a/k12 = 0.19. The CCl2 radical dimerizes and the energetic C2Cl4O* intermediate polymerizes. By competitive kinetics, the ratio k12/k13 was found to be 0.10, where k12 ≡ k12a + k12b and k13 is the rate coefficient of the O(3P) + C2F4 reaction.In the presence of O2, a chain process is involved in which CCl3CCl(O) and CCl2O are the major products. They are formed in a ratio of 2.0 independent of reaction conditions, but the chain length is proportional to [C2Cl4]/Ia1/2. Also produced is CO with a quantum yield of ∼0.18. The ratio Φ{CCl3CCl(O)}/Φ{CCl2O} = 2.0 is similar to that of 2.5 found in the Cl atom initiated oxidation. This result is interpreted to mean that chlorine atoms are involved in the chain. The reaction which initiates monoradicals in the system is[Formula: see text]