GB581254A - Improvements in or relating to the production of organic fluorine compounds - Google Patents

Abstract

Halofluoroalkanes are prepared by reacting in the presence of a Friedel-Crafts catalyst, a halogenated methane containing at least three halogen atoms but no fluorine, with a halogenated ethylenic compound having at least one atom of chlorine attached to one of the doubly-bonded carbon atoms, said ethylenic compound also containing at least one fluorine atom. Thus, ethylenic compounds having the general formula RR1C=CR2X, where R, R1 and R2 are hydrogen, fluorine, chlorine, alkyl or chlorinated or fluorinated alkyl, at least one of these substituents being fluorine or fluorinated alkyl and X is chlorine are operable in this process. Reaction temperatures up to 150 DEG C. may be used though preferably normal or slightly elevated temperatures are used, in general from 15 DEG to 100 DEG C. The preferred catalyst is aluminium chloride though other Friedel Crafts catalysts such as boron trifluoride, zinc chloride or ferric chloride may be used. The products may be isolated by destroying the catalyst, as by decomposition with ice or cold water, followed by distillation. Specified ethylenic compounds employable in the process are 1,2 - dichloro - 3 - trifluoro - 1 - propene, 1,1,2 - trichloro - 3 - trifluoro - 1 - propene, 1 - dichloro - 3 - trifluoro - 1 - propene, 1,1,3,3,3 - pentafluoro - 2 - chloro - 1 - propene, asym.-difluorodichloroethylene, sym.-dichlorodifluoroethylene, and trifluorochloroethylene. In examples: (1) chloroform and trifluorochloroethylene were reacted in the presence of aluminium chloride in a silver-lined high-pressure tube at 50 DEG C. and from the reaction products, tetrachlorotrifluoropropane and pentachlorodifluoro propane were recovered; (2) trifluorochloroethylene and carbon tetrachloride were reacted in the presence of aluminium chloride yielding pentachlorotrifluoropropane and hexachlorodifluoropropane. The products may be used as petroleum chemicals, dialectric fluids and cooling liquids. Specification 570,470 is referred to. The Specification as open to inspection under Sect. 91 comprises also the reaction of a halogenated methane containing at least three halogen atoms with a halogenated ethylenic compound having at least one atom of halogen other than fluorine attached to one of the doubly bonded carbon atoms and containing at least one fluorine atom, while in the formula given above, R, R1 and R2 may be any halogen or halogenated alkyl and X may be halogen. This subject-matter does not appear in the Specification as accepted.