Tetrachloroethylene photolysis

The photolysis of hexachloroacetone in the vapour phase has been studied by Hautecloque and in the liquid by Haszeldine and Nyman . The volatile products of the gas phase reaction were carbon tetrachloride, tetrachloroethylene, hexachloroethane and carbon monoxide, and the quantum yield for CO formation was 0.5 at 275 °C and 2 3130 A. These results suggest that primary processes of both Type 1 and Type 2 are occurring and that carbon monoxide is not readily formed from the trichloroacetyl radical... 

Carbon tetrachloride could be formed by the abstraction of a chlorine atom from a hexachloroacetone molecule by a trichloromethyl radical tetrachloroethylene could then result from the dimerisation of dichlorocarbene radicals produced from the dissociation of pentachloroacetonyl radicals. Haszeldine and Nyman identified trichloroacetyl chloride and octachloropropane as products of the liquid phase photolysis, suggesting a primary step of Type 3 involving rupture of the carbon-halogen bond. Photolysis in the liquid phase was found to be very slow, and this has been attributed to cage effects and recombination of radicals formed in the primary step. 

From the atmosphere, CCI4 is removed in reactions with free radicals by photolysis, hydrolysis and biological degradation after a preceding absorption (reactions with 0( D) are of particular importance [48]). Trichloroethylene and tetrachloroethylene are used extensively as industrial solvents of fats, waxes, bitumens, dyes, oils and paints. 

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