A faeilo monofluorination of α,ω-dihaloporfluoroalkanes was achieved by the reactionof them with antimony trifluoride and chlorine in anhydrous antimony pentachloride when mono-fluorinated products wero removed immediately after their formation from the reaction mixture byfractionation.The reaction conditions were also investigated. A faeilo monofluorination of α, ω-dihaloporfluoroalkanes was achieved by the reaction of them with antimony trifluoride and chlorine in anhydrous antimony pentachloride when mono-fluorinated products wero removed immediately after their formation from the reaction mixture by fractionation. The reaction conditions were also investigated.