Abstract Perfluoroalkanesulfonyl chlorides [RF SO 2 Cl; RF CF 3, C 2 F 3, C 4 F 9], decompose thermally to give the corresponding perfluoroalkyl chlorides with evolution of SO 2. The latter retards the reaction, but it is catalysed by copper which also inhibits the SO 2 effect. 2-methyl-2-nitrosopropane traps the perfluoroalkyl free radicals. In the presence of a perfluoroalkyl iodide [R′ FI≠ R′ F≠ RF], other products, RFI and RF Cl, are obtained. A ...