The Photochlorination and the Chlorine-Sensitized Photo-oxidation of Gaseous Tetrachloroethylene

In the absence of oxygen, the illumination of a carbon tetrachloride solution of chlorine and tetrachloroethylene with blue light has been found to bring about chlorination which proceeds as a chain reaction with a large quantum yield and at a rate proportional to the square root of the intensity of illumination. In the presence of oxygen, the chlorination is strongly inhibited and instead there occurs a chlorine-sensitized oxidation to trichloroacetyl chloride and phosgene; this reaction proceeds in solution with a comparatively small quantum yield and at a rate proportional to the first power of the light intensity. It was found possible to account for the kinetics of the chlorination by either of two simple and plausible reaction schemes, one involving C_2Cl_5 and the other Cl_3.