Derivatives of trifluorovinylsulfur pentafluoride (SF5CFCF2) II

Trifluorovinylsulfur pentafluoride (SF₅CFCF₂) and carbonyl fluoride will add, in the presence of cesium fluoride and acetonitrile, to form SF₅CF(CF₃)C(O)F. This new acid fluoride serves as a source for preparing derivatives containing the SF₅CF(CF₃) - grouping. The following new compounds have been prepared and characterized: SF₅CF(CF₃)X where X = C(O)F, C(O)CH₃, C(O)OH, C(O)NH₂, CN. The dimer, (SF₅CFCF₂)₂, has also been prepared. Infrared, mass, and nmr spectra are presented in order to support their proposed structure.     

Nickel Fluorocarbene Metathesis with Fluoroalkenes

Alkene metathesis with directly fluorinated alkenes is challenging, limiting its application in the burgeoning field of fluoro‐organic chemistry. A new nickel tris(phosphite) fluoro(trifluoromethyl)carbene complex ([P₃Ni]=CFCF₃) reacts with CF₂=CF₂ (TFE) or CF₂=CH₂ (VDF) to yield both metallacyclobutane and perfluorocarbene metathesis products, [P₃Ni]=CF₂ and CR₂=CFCF₃ (R=F, H). The reaction of [P₃Ni]=CFCF₃ with trifluoroethylene also yields metathesis products, [P₃Ni]=CF₂ and cis/trans‐CFCF₃=CFH. However, unlike reactions with TFE and VDF, this reaction forms metallacyclopropanes and fluoronickel alkenyl species, resulting presumably from instability of the expected metallacyclobutanes. DFT calculations and experimental evidence established that the observed metallacyclobutanes are not intermediates in the formation of the observed metathesis products, thus highlighting a novel variant of the Chauvin mechanism enabled by the disparate four‐coordinate transition states.     

An efficient dehyrohalogenation method for the synthesis of α,β,β-trifluorostyrenes, α-chloro-β,β-difluorostyrenes and E-1-arylperfluoroalkenes

Dehydrofluorination of 1-aryl-1,2,2,2-tetrafluoroethanes (ArCHFCF₃) and 1-aryl-1-chloro-2,2,2-trifluoroethane (ArCHClCF₃) using lithiumhexamethyldisilazide (LHMDS) in tetrahydrofuran (THF) at room temperature produced 1,2,2-trifluorostyrene and 1-chloro-2,2-difluorostyrene, respectively, in very good isolated yields. Dehydrofluorination of 1,2,2,3,3,3-hexafluoro-1-phenyl-propane (PhCHFCF₂CF₃) and 1,2,2,3,3,4,4,4-octafluoro-1-phenyl-butane (PhCHFCF₂CF₂CF₃) using LHMDS produced the corresponding substituted olefins (1-phenyl-1,2,3,3,3-pentafluoroprop-1-ene and 1-phenyl-1,2,3,3,4,4,4-pentafluorobut-1-ene) in good yield and high E-selectivity. Dehydrofluorination of 1-chloro-1-phenyl-2,2,3,3,3-pentafluoropropane (PhCHClCF₂CF₃) and 1-chloro-1-phenyl-2,2,3,3,4,4,4-heptafluorobutane (PhCHClCF₂CF₂CF₃) produced a mixture of the corresponding E and Z olefins (PhCClCFCF₃ and PhCClCFCF₂CF₃) in good yield.     

Some diels—alder reactions of η1-bonded cyclopentadienylmetal compounds

Bis(cyclopentadienyl)mercury readily undergoes Diels—Alder reactions with RCCR (R = CO₂Me or CF₃), CF₃CFCFCF₃, CF₃CFCF₂, (CF₃)₂CC(CN)₂, C₂(CN)₄ and Ph$\text{NCONNC}$O to give stable adducts characterised by¹H, ¹⁹F and ¹³C NMR, spectroscopy. Similar reactions of CF₃CCCF₃ and CF₃CFCFCF₃ with the cyclopentadiene derivatives Me₃MC₅H₅ and (Me₃M)₂C₅H₄ (M = Si, Sn) are also described.     

Fluorocyclohexanes. Part XVI. The six H-trifluoromethyldecafluoro- and two of the 2H,4H-trifluoromethylnonafluoro-cyclohexanes

Fluorination of benzotrifluoride by cobaltic fluoride at 260–280° gave, besides the fluorocarbon, the six possible tridecafluoromethylcyclohexane isomers, and two 2H,4H-dodecafluorides. Of the C₇HF₁₃ compounds, only the cis?2H-, and the cis- and trans-4H-isomers could be isolated pure. The two 3H-isomers were made by pyrolysis of perfluoro(1-methyl-3-isopropylcyclohexane) in the presence of toluene. The trans-2H-isomer was made by further fluorination of one of the 2H,4H-dodecafluorides. Aqueous potash and the cis-2H-tridecafluoride gave 1-trifluoromethylnonafluorocyclohex-1-ene, which with stronger alkali hydrolysed to 1-carboxynonafluorocyclohex-1-ene. The cis- and trans- 2H and 4H-tridecafluorides were dehydrofluorinated by sodium fluoride at 320–380° (the cis-isomer of each pair reacted faster than the trans- : axial versus equatorial hydrogen) to give, respectively, the 1-trifluoromethylnonafluoro-ene and the 4-trifluoromethyl-isomer. The latter was isomerised to the former by sodium fluoride at 500–600°. The 1?CF₃-ene gave hexafluoroglutaric acid on oxidation with alkaline potassium permanganate.     

Temperature-induced transformations of peroxide radicals formed in polytetrafluoroethylene with γ-ray irradiation

At 200°C, temperature-induced transformations of peroxide radicals from ? CF₂CF(OO·)CF₂? (radical I) to ? CF₂CFCF₂? (radical 1) and ? CF₂CF₂OO· (radical II) to ? CF₂CF₂ (radical 2) in vacuo, and from I to II in oxygen atmosphere were observed. In these thermal transformations, the evolution of CO₂ with a small amount of CO and CF₂O was observed. Further, measurements of the heat of crystallization of the treated polytetrafluoroethylene suggest that a reduction of polymer molecular weight occurs during the transformations from I to 1 and I to II.     

Cycloaddition reaction of quadricyclane and fluoroolefins

Reaction of quadricyclane (1) with fluoroolefins of different structure results in stereoselective formation of polyfluorinated exo-tricyclo[4.2.1.0^2,5]non-7-enes. The reaction of a mixture of trans/cis CF₃CFCFCF₃ with 1 is stereoselective and the resulting cycloadducts 7a, b preserve the original alkene stereochemistry. The relative rate constants of cycloaddition of a series of fluoroolefins to 1 under pseudo first-order conditions measured by kinetic NMR at 109 °C provide a kinetic scale of reactivities of the fluoroolefins in this reaction.These relative rate constants correlate well with the number of fluoroalkyl groups connected to the double bond, reaching a maximum for the tri-substituted olefin: CF₃CFCF₂:CF₃CFCFCF₃:(CF₃)₂CC(CF₃)₂:(CF₃)₂CCFC₂F₅ = 1:1.2-1.9:4:138.     

Transition-Metal-Free Controllable Single and Double Difluoromethylene Formal Insertions into C−H Bonds of Aldehydes with TMSCF2Br

We have developed a new strategy for controllable single and double difluoromethylene (CF₂) formal insertions into C−H bonds of aldehydes with nearly full selectivity under transition-metal-free conditions. The key to the success of controllable CF₂ insertions lies in the well-defined formation of 2,2-difluoroenolsilyl ether and 2,2,3,3-tetrafluorocyclopropanolsilyl ether intermediates using difluorocarbene reagent TMSCF₂Br (TMS=trimethylsilyl). These two intermediates can react with various electrophiles including proton sources and various halogenation reagents, allowing for the access to diverse arrays of ketones containing difluoromethylene (CF₂) and tetrafluoroethylene (CF₂CF₂) units. The first synthesis of relatively stable 2,2,3,3-tetrafluorocyclopropanolsilyl ethers has been achieved, which offers a new platform to explore other unknown chemical space.     

Fluorinated phosphorus compounds: Part 6. The synthesis of bis(fluoroalkyl) phosphites and bis(fluoroalkyl) phosphorohalidates

Reaction of phosphorus trichloride with tert-butanol and fluoroalcohols gave bis(fluoroalkyl) phosphites (R_FO)₂P(O)H in 42-89% yield, where R_F=HCF₂CH₂, H(CF₂)₂CH₂, H(CF₂)₄CH₂, CF₃CH₂, C₂F₅CH₂, C₃F₇CH₂, (CF₃)₂CH, (FCH₂)₂CH, CF₃(CH₃)₂C, (CF₃)₂CH₃C, CF₃CH₂CH₂, C₄F₉CH₂CH₂ and C₆F₁₃CH₂CH₂. Treatment of these with chlorine in dichloromethane gave the bis(fluoroalkyl) phosphorochloridates (R_FO)₂P(O)Cl in 49-96% yield. The chloridate (CF₃CH₂O)₂P(O)Cl was isolated in much lower yield from the interaction of thionyl chloride with bis(trifluoroethyl) phosphite. Heating the latter in dichloromethane with potassium fluoride and a catalytic amount of trifluoroacetic acid gave the corresponding fluoridate (CF₃CH₂O)₂P(O)F in 84% yield. Treatment of bis(trifluoroethyl) phosphite with bromine or iodine gave the bromidate (CF₃CH₂O)₂P(O)Br and iodidate (CF₃CH₂O)₂P(O)I in 51 and 46% yield, respectively. The iodidate is the first dialkyl phosphoroiodidate to have been isolated and characterised properly—its discovery lags behind the first isolation of a dialkyl phosphorochloridate by over 130 years. The fluoroalkyl phosphoryl compounds are generally more stable than known unfluorinated counterparts.     

Preparation of 1‐X‐2, 2‐Difluoroethenylxenon(II) Tetrafluoroborates [CF2=CXXe][BF4]

The new type of alkenylxenon(II) salts [CF₂=CXXe] [BF₄] (X = H, Cl, CF₃) was prepared by reacting the corresponding alkenyldifluoroboranes CF₂=CXBF₂ with XeF₂ in 1, 1, 1, 3, 3‐pentafluoropropane (PFP) at —60 °C. The alkenylxenon(II) salts were characterised by multinuclear NMR spectroscopy. The influence of the substituent X at C‐1 on the stability of alkenylxenon(II) salts is discussed. Additionally the preparation of the potassium alkenyltrifluoroborate salts K [CF₂=CXBF₃] and their transformation into the boranes CF₂=CXBF₂ by fluoride abstraction in PFP is reported.     

Model compounds and monomers derived from 1,1-difluoroethene

Saturated model compounds, related to elastomers that are derived from copolymers of CH₂=CF₂/CF₂=CFCF₃, have been synthesised and studied. Unsaturated compounds were obtained by both base- and Lewis-acid induced processes. Some reactions with antimony pentafluoride lead to remarkably stable carbocations, and even di-cations, and the nmr data for these systems is revealing about structure. Polyconjugated polymers may be obtained by this procedure. Preliminary studies are described, relating to the incorporation of crowded monomers into fluorocarbon polymers, ultimately, as a means of initiating cross-linking processes for curing elastomers.     

Bromodifluoroacetyl fluoride,CF2BrC(O)F: Experimental and theoretical studies

Bromodifluoroacetyl fluoride, CF₂BrC(O)F, was prepared through the gas-phase reaction of bromotrifluoroethene, CF₂CFBr, with molecular oxygen initiated either by NO₂ or CF₃OF. The compound was experimentally studied by FTIR spectroscopy of the gas phase and also isolated in Ar and N₂ matrices at low temperature. The energy differences between the possible conformers were theoretically studied, as well as the vibrational spectra of the conformers.     

Atmospheric chemistry of CF3CFCH2: Products and mechanisms of Cl atom and OH radical initiated oxidation

The products of Cl atom and OH radical initiated oxidation of CF₃CFCH₂ were studied in 700 Torr of N₂/O₂ diluent at 296 ± 1 K. The reactions of Cl atoms and OH radicals with CF₃CFCH₂ proceed via electrophilic addition to the double bond. The reaction with chlorine atoms proceeds 56 ± 5% via addition to the central carbon. The chlorine atom initiated oxidation of CF₃CFCH₂ gives CF₃C(O)F in a molar yield which is indistinguishable from 100% and independent of [O₂], and HC(O)Cl in a molar yield which increased from 30% to 59% as [O₂] was increased from 3 to 700 Torr. The OH radical initiated oxidation of CF₃CFCH₂ gives CF₃C(O)F as major product in a yield of 91 ± 6%. The results are discussed with respect to the atmospheric chemistry and environmental impact of CF₃CFCH₂.     

Dissociation and IVR pathways for the CF3H(H2O)3 cluster

Classical trajectory simulations are used to study the intramolecular dynamics of isolated CF₃H and the CF₃H(H₂O)₃ cluster, by either exciting the CH stretch local mode to then=6 level or by adding an equivalent amount of energy to an OH stretch normal mode. Energy transfer from the CH local mode is statistically the same for CF₃H(H₂O)₃ as for isolated CF₃H, and agrees with previous experimental studies. Clusters excited with 6 quanta in the CH local mode are remarkably stable. Though the CF₃H-(H₂O)₃ intermolecular potential is only 1.5 kcal/mol, only 1 of 26 clusters excited with 6 quanta in the CH local mode dissociate within 10 ps. The absorption linewidth for the CH local mode in CF₃H(H₂O)₃ is related to IVR within CF₃H and not to the unimolecular lifetime of the cluster. When an OH stretch normal mode of the cluster is excited, energy transfer to CF₃H is negligible and nearly one half of the clusters dissociate within 10 ps.     

Reactions of amines with a dimer of hexafluoropropene and with a perfluorovinyl sulfide prepared with hexafluoropropene

Some reactions of amines with a perfluorovinylsulfide, (CF₃)₂CFSC(CF₃)CFCF(CF₃)₂, prepared from hexafluoropropene (HFP) and sulfur [1] are compared to reactions of the same amines with the thermodynamic dimer of HFP, (CF₃)₂CCFCF₂CF₃. Many new ketenimines, eneamines, amidines, nitriles, and quinoline derivatives are reported.     

Hydrogen abstraction from CF3CF2CFH2 and CF3CFHCF2H by OH radicals and Cl atoms: theoretical enthalpies and rate constants

The hydrogen abstraction reactions of CF₃CF₂CFH₂ and CF₃CFHCF₂H with OH radicals and Cl atoms have been studied theoretically by a dual-level direct dynamics method. Two stable conformers of CF₃CF₂CFH₂ with C _s and C ₁ symmetries and all possible abstraction channels for each reaction are all taken into consideration. Optimized geometries and frequencies of all the stationary points and extra points along minimum-energy path (MEP) have been computed at the BB1K/6-31+G(d, p) level of theory. To refine the energy profile of each reaction channel, single point energy calculations have been performed by the BMC-CCSD method. The rate constants are evaluated by canonical variational transition state theory (CVT) with the small-curvature tunneling correction method (SCT) over a wide temperature range of 200–1,000 K. The detailed branching ratios of four reactions are discussed. The good agreement found between our theoretical rate constants and the available experimental data suggests that the present approach could provide a reliable prediction for the CF₃CFHCF₂H + Cl reaction about which there is little experimental information. The kinetic calculations show that the SCT effect plays an important role in all channels. In addition, in order to further reveal the thermodynamic properties, the enthalpies of formation of the reactants (CF₃CF₂CFH₂ and CF₃CFHCF₂H) and the product radicals (CF₃CF₂CFH, CF₃CFCF₂H, and CF₃CFHCF₂) are evaluated by applying isodesmic reactions at both BMC-CCSD//BB1K/6-31+G(d, p) and MC-QCISD//BB1K/6-31+G(d, p) levels of theory.     

Kinetics and products of chlorine atom initiated oxidation of HCF2OCF2OCF2CF2OCF2H and HCF2O(CF2O)n‐(CF2CF2O)mCF2H

Smog chamber/FTIR techniques were used to measure k(Cl + HCF₂OCF₂OCF₂‐CF₂OCF₂H) = k(Cl + HCF₂O(CF₂O)_n(CF₂CF₂O)_mCF₂H) = (5.0 ± 1.4) × 10^?17 cm³ molecule^?1 s^?1 in 700 Torr of N₂/O₂ diluent at 296 ± 1 K. The Cl‐initiated atmospheric oxidation of HCF₂OCF₂OCF₂CF₂OCF₂H and the sample of HCF₂O(CF₂O)_n(CF₂CF₂O)_mCF₂H used in this work gave COF₂ in molar yields of (476 ± 36)% and (859 ± 63)%, respectively, with no other observable carbon containing products (i.e., essentially complete conversion of both hydrofluoropolyethers into COF₂). The results are discussed with respect to the atmospheric chemistry and environmental impact of hydrofluoropolyethers of the general formula HCF₂O(CF₂O)_n(CF₂CF₂O)_mCF₂H. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 819–825, 2008     

Thermal gas-phase reaction of perfluorobuta-1,3-diene with NO2

The reaction of NO₂ with perfluorobuta-1,3-diene, CF₂CFCFCF₂ (C₄F₆), has been studied at 312.9, 323.0, 333.4, 396.0 and 418.0 K, using a conventional static system. The products formed in the temperature range 312.9-333.4 K were CF₂CFCF(NO₂)CF₂(NO₂) (I), CF₂(NO₂)CFCFCF₂(NO₂) (II), CF₂CFCF(NO₂)C(O)F (III) and CF₂(NO₂)CFCFC(O)F (IV) and FNO. The formation of these compounds was detected performing infrared and Raman spectra. The infrared spectrum shows a band at 1785 cm⁻¹, characteristic to the terminal -CFCF₂ group and the Raman spectrum shows a band located at 1733 cm⁻¹, corresponding to -CFCF- group. It indicates, that in this temperature range, NO₂ attacks initially only one double bound of CF₂CFCFCF₂. Since the intermediate radical CF₂CFCFCF₂(NO₂) formed in this process is allylic in nature, so there is no isomerization involved in this process, but rather the allylic radical is able to add the second NO₂ either to CF₂ or CFCF₂(NO₂) end, forming the corresponding products. At 396.0 and 418.0 K different products were observed: CF₂(NO₂)CF(NO₂)C(O)F (V), NO, CF₃C(O)F, C(O)F₂ and traces of epoxide of tetrafluoroethene, showing that, at these temperatures, both double bonds are attacked by NO₂ and detachment of CF₂ group is produced. The mechanisms consistent with experimental results in the temperature range 312.9-333.4 and at 396.0 and 418 K are proposed.     

Hydrogen abstraction reactions of OH radicals with CF<Subscript>2</Subscript>ClCClXH (X = F,Cl) and CFCl<Subscript>2</Subscript>CClXH (X = F,Cl): a mechanistic and kinetic study

The reactions of OH (OD) radicals with CF₂ClCClFH (R1), CF₂ClCCl₂H (R2), CFCl₂CClFH (R3), and CFCl₂CCl₂H (R4) have been investigated theoretically by a dual-level direct dynamics method. The optimized geometries and frequencies of the stationary points are calculated at the MPW1K/6-311+G(d,p) level. To improve the reaction enthalpy and potential barrier of each reaction channel, the single-point energy calculation is made by the MC-QCISD method. The enthalpies of formation of the species CF₂ClCClFH, CF₂ClCCl₂H, CFCl₂CClFH, CFCl₂CCl₂H, CF₂ClCClF, CF₂ClCCl₂, CFCl₂CClF, and CFCl₂CCl₂ are evaluated by two sets of isodesmic reactions. Using canonical variational transition state theory (CVT) with the small-curvature tunneling correction (SCT) method, the rate constants of OH and OD radicals with CF₂ClCClXH (X = F, Cl) and CFCl₂CClXH (X = F, Cl) are evaluated over a wide temperature range of 100–2,000 K at the MC-QCISD//MPW1K/6-311+G(d,p) level. The calculated CVT/SCT rate constants are consistent with available experimental data. The results show that the tunneling correction has an important contribution in the calculation of rate constants at lower temperatures. For the above-mentioned four reactions, the kinetic isotope effects are also calculated. Finally, the effect of fluorine or chlorine substitution on reactivity of the C–H bond is discussed.     

Preparation of cis-1,1,1,4,4,4-hexafluorobut-2-ene by cis-selective semi-hydrogenation of perfluoro-2-butyne

Cis-1,1,1,4,4,4-hexafluorobut-2-ene has a zero ozone depletion potential (ODP), low global warming potential (GWP) and non-flammable properties, so it is believed to be a potential foam expansion agent. For the synthetic process of cis-1,1,1,4,4,4-hexafluorobut-2-ene, the process catalysts are the key factors for its yield and cost. In this paper, the catalysts of palladium attached to porous aluminum fluoride, to active carbon, to Al₂O₃, and the blends of palladium and bismuth to AlF₃ used to prepare cis-1,1,1,4,4,4-hexafluorobut-2-ene by cis-selective semi-hydrogenation of perfluoro-2-butyne were investigated. The performance of above-mentioned catalysts was compared in reaction process. The experimental results indicate that the additive of bismuth to palladium catalyst is useful for improving the activity and selectivity compared to Pd/C and Pd/Al₂O₃. The role of bismuth in the synthetic process is discussed based on the experimental results and theory analysis.