Fluoro-olefin chemistry. Part 17. Thermal reaction of hexafluoropropene with 2-trifluoromethylbutane and 1,1,1-trifluoropentane

Abstract

Reaction of hexafluoropropene with 2-trifluoromethylbutane (1) and 1,1,1-trifluoropentane (2) in the range 260–295 °C gives as major products the 1:1 adducts CF₃CHMeCH₂CH₂CF₂CHFCF₃(10) and CF₃CH₂CH₂CHMeCF₂CHFCF₃(14), respectively, formed via hydrogen abstraction from C–H bonds γ to the CF₃ group. However, dehydrogenation to give 1H,2H-hexafluoropropane (6) and the alkenes CF₃CMe:CHMe (7)[from (1)] and CF₃CH₂CH₂CH:CH₂(22)[from (2)] is a competing reaction which is more important the higher the temperature. The alkene (7) reacts further to give CF₃CMe:CHCH₂CF₂-CHFCF₃(9) and the cyclopentane CF₃[graphic omitted]FCF₃(18) while the alkene (22) undergoes cyclodimerisation with hexafluoropropene to afford CF₃[graphic omitted]HCH₂CH₂CF₃(11) and then the dehydrogenation product CF₃[graphic omitted]HCH:CHCF₃(13). A further product from the alkane (2) is the olefin CF₃CH:CHCH₂CH₂CF₂CHFCF₃(12) formed via hydrogen abstraction from a δ-C–H bond. Reaction does not occur between 1,1,1-trifluoro-4-trifluoromethylpentane and hexafluoropropene at 295 °C.