sub 2 cclh sub 2hcfc 253cb ch sub 3 cf sub 2 cfclh______________________________________ hcfc 234cc may be formed by any known method such as the reaction of 1 1 1 2 2 3 hexachloropropane with antimony pentachloride and hydrogen fluoride at 100 u00b0 c hcfc 234cd may be formed by any known method such as the reaction of 1 1 1 trichloro 2 2 3 trifluoropropane with antimony pentachloride and hydrogen fluoride at 120 u00b0 c hcfc 244ca may be formed by any known method such as the reaction of 1 1 2 2 3 pentachloropropane with antimony pentachloride and hydrogen fluoride at 100 u00b0 c hcfc 244cb may be formed by any known method such as the reaction of 1 chloro 1 1 2 2 tetrafluoropropane with cesium fluoride and tetrabutylammonium bromide at 150 u00b0 c hcfc 253ca may be formed by any known method such as the reaction of 1 2 3 trichloro 2 fluoropropane with niobium pentachloride and hydrogen fluoride at 100 u00b0 c hcfc 253cb may be formed by any known method such as the reaction of 1 1 2 2 tetrachloropropane with tantalum pentafluoride and hydrogen fluoride at 130 u00b0 c the present method removes most contaminants from the surface of a substrate for example the present.