Telomerisation reactions have been investigated for the alkenes 1,1-di
fluoroethene (5) and hexafluoropropene (3) with the telogens CF2Br2 (1
), CF3CFBr2 (8) and CF3CBr3 (9), as a means of preparing telomers and
co-telomers. The efficiency of chain transfer increases as 1 less than
or equal to 8<9. Surprisingly, co-telomerisations of 5 with 3 occurre
d more efficiently than the corresponding telomerisations with 5 alone
. The effects of solvent are described.