2994-71-0Relevant articles and documents
2π + 2π cycloaddition kinetics of some fluoro olefins and fluoro vinyl ethers
Wlassics, Ivan
, p. 1519 - 1528 (2004)
The second order 2π + 2π homo- and co-dimerization between various classes of fluorinated olefins has been investigated. The fluorinated olefins examined in this study were: (1) Rf-OCF=CF2 (perfluorinated vinyl ethers); (2) Rf-CF=CF2 (perfluorinated terminal olefins); (3) R-CH2-CF=CF2; (4) Ph-OCF=CF2 (aryl perfluorinated vinyl ethers). Homo-dimerizations between vinyl ethers have an Ea between 20 and 24 kcal 1 mol-1 while homo-dimerizations between terminal olefins have an average Ea between 35 and 40 kcal mol-1; vinyl groups have a second order cyclodimerization rate constant of formation between 1 × 10-7 and 1 × 10-4 M-1 S-1 while vinyl ethers have a second order cyclodimerization rate constant of formation = 1 × 10-1 M-1 S-1. If there is a -CH2- group α to the terminal olefin, the Ea of cyclodimerization is about 7 kcal mol-1) lower with respect to those olefins with a -CF2-α to the instauration. At 270 °C co-dimerizations have an average ΔS≠ = -45 cal K-1 mol-1 and a second order rate constant of cyclodimerization ranging between 0.1 × 10-4 and M-1 S-1 while homo-dimerizations have an average ΔS≠ = -17 cal K-1 mol-1 and a second order rate constant which can span from 7 × 10-1 M-1 S-1 to as much as 1 × 10-1 M-1 S-1 depending on the electronic nature of the perfluorinated terminal olefin. A good correlation between the electronegativity x and the activation energy Ea demonstrates that polarizing groups, -O-, PhO, α to the olefin play an important role in the formation and stabilization of the cyclodimerization biradical intermediate.
Fluoro-olefin Chemistry. Part 17. Thermal Reaction of Hexafluoropropene with 2-trifluoromethylbutane and 1,1,1-Trifluoropentane
Davies, Terry,Haszeldine, Robert N.,Tipping, Anthony E.
, p. 1353 - 1356 (2007/10/02)
Reaction of hexafluoropropene with 2-trifluoromethylbutane (1) and 1,1,1-trifluoropentane (2) in the range 260-295 deg C gives as major products the 1:1 adducts CF3CHMeCH2CF2CHFCF3 (10) and CF3CH2CH2CHMeCH2CF2CHFCF3 (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) and CF3CH2CH2CH:CH2 (22) is a completing reaction which is more important the higher the temperature.The alkene (7) reacts further to give CF3CMe:CHCH2CF2CHFCF3 (9) and the cyclopentane (18) while the alkene (22) undergoes cyclodimerisation with hexafluoropropene to afford (11) and then the dehydrogenation product (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 deg C.
Fluoro-olefin Chemistry. Part 15. Thermal Reaction of Hexafluoropropene with Hydrocarbon Olefins
Haszeldine, Robert N.,Raynor, Clive M.,Tipping, Anthony E.
, p. 2219 - 2226 (2007/10/02)
The thermal reaction of hexafluoropropene with hydrocarbon olefins can give three different types of product, 1,1,2-trifluoro-2-trifluoromethylcyclobutanes, hexafluoroalkenes of the type R1R2C=CR3CH2CHFCF2CF3, and 1,1,2-trifluoro-2-trifluoromethylcyclopentanes.The cyclobutanes are formed via diradical intermediates and the cyclopentanes via intermediate allyl-radical attack on the fluoro-olefin, while the hexafluoroalkenes arise via either of these radical intermediates or by the 'ene' reaction.With olefins of the type CH2=CHR (R = Me or Et), cyclobutanes are formed exclusively, while those such as CH2=CMeR (R = Et or i-Pr) give both cyclobutanes and hexafluoroalkenes.However, the olefins CH2=CMe2, CHMe=CMe2, and CMe2=CMe2 afford all three types of product, but only with alkene CHMe=CMe2 is cyclopentane-formation a major reaction (29percent at 270 deg C and 35percent at 220 deg C).Certain of the reactions are complicated by hydrocarbon-olefin isomerisation.
