Oxygen effect in the photochlorination of trichloroethylene

The oxygen effect in the gas-phase photochlorination of trichloroethylene has been investigated at 363 and 403°K in a conventional kinetic apparatus and in a reaction cell combined with a rapid mass spectrometer. Once initiated by light at 4358 Å, the chlorination in presence of oxygen proceeds further in the dark. This " after-effect " has been investigated under various experimental conditions. The results can be represented by a reaction mechanism comprising (i) formation and decomposition of a peroxidic radical, (ii) the accumulation of a semi-stable peroxidic compound during the period of illumination, (iii) its monomolecular decomposition in the gas-phase to give free radicals both in the light and dark periods, (iv) the monomolecular destruction of the semi-stable peroxide at the wall to yield a stable product(s). Relevant rate constants have been measured. The values obtained and the results of mass spectrometric experiments imply that the semi-stable compound could be a peroxidic dimer such as Cl4HC2-O-O- C2HCl4.SCOPUS: ar.j