Process for preparing fluorinated compound

A process for preparing a fluorinated compound of the formula:

• R--CCl.sub.2 CF.sub.2 CF.sub.3 (I)
• wherein R is a perfluoroalkyl group, a perchloroalkyl group, a polyfluoroalkyl group, a polychloroalkyl group or a polychloropolyfluoroalkyl group, each having at least one carbon atom, which process comprises
• reacting, at a reaction temperature from -20.degree. C. to +150.degree. C., tetrafluoroethylene with at least one compound (II) selected from the group consisting of CF.sub.3 CFCl.sub.2, CF.sub.3 CF.sub.2 CFCl.sub.2, ClCF.sub.2 CFCl.sub.2, ClCF.sub.2 CFClCFCl.sub.2, CFCl.sub.2 CF.sub.2 CFCl.sub.2, CF.sub.3 CF.sub.2 CF.sub.2 CFCl.sub.2, ClCF.sub.2 CFClCF.sub.2 -CFCl.sub.2, HCF.sub.2 CF.sub.2 CFCl.sub.2 and HCF.sub.2 CF.sub.2 CF.sub.2 CF.sub.2 CFCl.sub.2 in the presence of a Lewis acid,
• wherein said Lewis acid is at least one member selected from the group consisting of anhydrous aluminum chloride, anhydrous zirconium tetrachloride, anhydrous zinc chloride, anhydrous tin chloride, anhydrous titanium tetrachloride, anhydrous iron chloride, anhydrous antimony pentachloride, anhydrous aluminum chlorofluoride, anhydrous zirconium chlorofluoride, anhydrous zinc chlorofluoride, anhydrous tin chlorofluoride, anhydrous titanium chlorofluoride, anhydrous iron chlorofluoride and anhydrous antimony chlorofluoride.