Photolysis of 1,1,1‐difluorochloroethane (Freon 142) at 147 nm

1,1,1‐Difluorochloroethane (Freon 142) was photolyzed at 147 nm in the pressure range of 3.6–20.6 torr. The effects of added NO, H 2 S, and CF 4 were investigated. The extinction coefficient at 147 nm and 296°K was determined to be 64 ± 8 atm −1 · cm −1 . The molecule photodecomposes largely by α,β elimination of HCl to give 1,1‐difluoroethylene (Φ = 0.74 ± 0.06). There is no observable elimination of HF, but there is strong evidence for the elimination of the elements of FCl though the relative importance of this process is minor, as are contributions from carboncarbon and carbonhalogen bond fission. The 1,1‐difluoroethylene formed is undoubtedly vibratonally excited and is the source of a pressure‐dependent small yield of fluoroacetylene. Over the pressure range studied there is no evidence that the major primary process itself is affected by changes in total pressure as is the case in the 147‐nm photolysis of ethyl chloride.