1.1.1- Trichloro-2,2-difluoroethane

Trichloroethene and cobalt(III) fluoride react at 120°C to give111 l,l,2-trichloro-l,2,2-trifluoroethane (26%) and l,l,2,2-tetrachloro-l,2-difluoroethane (10%) as major products, and the simple fluorine adduct, l,l,2-trichloro-l,2-difluoroethane (5%), as a minor product (seven products are identified). With manganese(III) fluoride at 220"C, the simple adduct111 is the major product (40 %), as it is112 (70 %) with potassium tetrafluorocobaltate(III) at 250 CC. 

The ease of dehydrohalogenation of alkyl halides decreases along the series RI > RBr > RC1 > RF. The rate of elimination of hydrogen chloride from l,2,2-trichloro-l,l-difluoroethane (20) is about 55 times as high as the rate of elimination of hydrogen fluoride from 2,2-dichloro-l,l,l-trifluoroethane (22), to give l,l-dichloro-2,2-difluoroethene (21).20... 

As discussed (vide supra) disproportionation and isomerization are often competitive reactions. The reaction rates of both types depend on the temperature and the catalyst used for the reaction. Chromium(III) oxide on support, or without, favors the disproportionation of 1,1,2-trichloro-1.2,2-trifluoroethane to give l,l-dichloro-l,2.2,2-tetrafluoroethane and 1,1,1.2-tetra-chloro-2,2-difluoroethane whereas with aluminum trifluoridc the isomerization is favored.24 The higher the chlorine content of the molecules the greater is their reactivity. 

Hydrochlorofluorocarbons, or HCFCs, are being promoted as temporary replacements for CFCs. HCFCs, unlike CFCs, have at least one C-H bond. HCFCs are not less prone than CFCs to decompose in the stratosphere, but there is a pathway by which HCFCs can decompose in the lower atmosphere (where they cannot damage ozone) that is not accessible to CFCs. 2,2,2-Trichloro-l,l-difluoroethane, CHF2CCI3, is a typical HCFC. 

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