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 18. Thermal Reaction of Hexafluoropropene with Diphenylmethane, Butylbenzenes, Benzyl Alcohol, and Benzyl Methyl Ether
Haszeldine, Robert N.,Raynor, Clive M.,Tipping, Anthony E.
, p. 2801 - 2806 (2007/10/02)
The thermal reaction of hexafluoropropene with diphenylmethane gives the 1:1 adduct Ph2CHCF2CHFCF3 (4a) and the rearranged adduct PhCH2CF2CFPhCF3 (5a) via benzylic hydrogen abstraction.Analogous 1:1 adducts are formed from benzyl alcohol in low yield, i.e.PhCH(OH)CF2CHFCF3 (4e) and HOCH2CF2CFPhCF3 (5b), but the reaction is complicated by decomposition of the alcohol to benzaldehyde, toluene, and water followed by the formation of the toluene-hexafluoropropene adduct PhCH2CF2CHFCF3 (4c).A similar decomposition is observed with benzyl methyl ether and compound (4c) is the only fluorinated product isolated.With n-butylbenzene the 1:1 adduct PhCHPrnCF2CHFCF3 is formed in relatively low yield due to rearrangement of the intermediate radical PhCHPrnCF2C(*)FCF3 by a 1,5-hydrogen shift followed by β-scission to give the radical PhC(*)HCF2CHFCF3 and propene and hence (4c) and the cyclobutane (8a), respectively.With isobutylbenzene the only 1:1 adduct isolated is PhCH2CMe2CF2CHFCF3, although benzylic hydrogen abstraction does occur as shown by the formation of compounds (4c) and (8a). 1:1 Adducts are not detected in the products from the reaction with s-butylbenzene; the intermediate radical PhCMeEtCF2C(*)FCF3 undergoes (i) cyclisation to give the indan (12), (ii) decomposition to give the olefin CF2:CMeEt and the radical PhC(*)FCF3 and (iii) rearrangement followed by β-scission to give ethylene and the radical PhC(*)MeCF2CHFCF3.
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.
