The Hg 6(3P)-Photosensitized Oxidation of C2Cl4

The Hg 6(3P) sensitized photolysis of C2Cl4 was studied at 25 °C both in the absence and presence of N2O and O2. For C2Cl4 alone, the only products are polymer and Hg2Cl2. The quantum yield of C2Cl4 disappearance, −Φ{C2Cl4} ∼ 1. Thus, the photolysis produces C2Cl3 radicals and Hg2Cl2, the C2Cl3 radicals dimerize, and the resultant 1,3-C4Cl6 polymerizes. The relative quenching of Hg 6(6P) by C2Cl4 compared to N2O is 3.0.In the presence of O2 the products are CCl3CCl(O) and CCl2O which are formed in a radical chain process in a ratio of 2.6 independent of reaction conditions. CO is also produced with a quantum yield of unity. The quantum yields of the chlorine-containing products are independent of the O2 pressure and the absorbed intensity, but are proportional to the C2Cl4 pressure, the proportionality constants being 1.4 and 3.7 Torr−1, respectively, for CCl2O and CCl3CCl(O). A detailed mechanism, based on the chlorine atom chain oxidation, is presented, and appropriate rate constant ratios are evaluated.