Trifluoromethane from photolysis

Trifluoromethyl radicals are generated from the photolysis of hexafluoroacetone. In the presence of trichlorosilane the hydrogen atom is abstracted with formation of trifluoromethane (2). The competitive abstraction of chlorine atoms does not occur. 

Hexafluorobiacetyl. In the gas phase, hexafluorobiacetyl behaved 169> in the same manner as biacetyl, affording carbon monoxide and hexa-fluoroethane in stoichiometric ratio. However, in the presence of hydrocarbon vapor or in hydrocarbon solution, the disappearance of dione was not accompanied by formation of cleavage products. For example, photolysis (A >3000 A, 65°) of hexafluorobiacetyl in 150 molar excess of 2,3-dimethylbutane until 84% of starting material had disappeared resulted in only 0.5% of carbon monoxide, an equivalent amount of trifluoromethane, and a complex mixture of other products. On the basis of carbonyl and hydroxyl absorption in the infrared, it was assumed that the excited dione abstracted hydrogen from hydrocarbons to give products of photoreduction, photoaddition, etc. Occurrence of H-abstraction in the gas phase is unique. 

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