- Oxidation of hexafluoropropylene with oxygen to hexafluoropropylene oxide
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A method for pressure oxidation of hexafluoropropylene (HFP) with oxygen to hexafluoropropylene oxide (HFPO) has been presented. The oxidation was carried out in a periodically operated reactor. The influence of temperature, the nature of the solvent, and the molar ratio of HFP/O2 on the course of oxidation was investigated during the preliminary studies. The magnitudes describing the process were the conversion of HFP, the selectivity of transformation to HFPO in relation to HFP consumed, and the yield of HFPO in relation to the initial amount of HFP. The optimisation of the technological parameters of oxidation, temperature, HFP/O2 molar ratio, and the reaction time was performed by the application of a statistical experimental design method. The function describing the process was the yield of HFPO.
- Wroblewska, Agnieszka,Milchert, Eugeniusz,Meissner, Egbert
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body text
p. 272 - 277
(2010/04/28)
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- Insertion reactions of difluorocarbene generated by pyrolysis of hexafluoropropene oxide to O-H bond
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ROCHF2-type fluorinated ethers were synthesized by the reaction of hexafluoropropene oxide (HFPO) with alcohol or phenol. In this reaction, although the insertion reaction of difluorocarbene to OH bond and the nucleophilic attack of alcohol or
- Mizukado, Junji,Matsukawa, Yasuhisa,Quan, Heng-Dao,Tamura, Masanori,Sekiya, Akira
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p. 373 - 377
(2007/10/03)
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- Preparation of highly fluorinated cyclopropanes and ring-opening reactions with halogens
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Various highly fluorinated cyclopropanes 1 were prepared by reaction of the appropriate fluorinated olefins with hexafluoropropylene oxide (HFPO) at 180 °C. The fluorinated nitrile le was converted to the triazine derivatives 2a and 2b by catalysis with Ag2O and NH3/(CF3CO)2O, respectively. The fluorinated cyclopropanes reacted with halogens at elevated temperatures to provide the first useful, general synthesis of 1,3-dihalopolyfluoropropanes. At 150-240 °C, hexafluorocyclopropane and halogens X2 produce XCF2CF2CF2X (X = Cl, Br, I) in 50-80% isolated yields. Pentafluorocyclopropanes c-C3F5Y [Y = Cl, OCF3, OC3F7 and OCF2CF(CF3)OCF2CF2Z; Z = SO2F, CN, CO2Me] react regiospecifically at 150 °C to give XCF2CF2CFXY, c-C3F5Br reacts regioselectively with Br2 to give a 16.7:1 mixture of BrCF2CF2 CFBr2:BrCF2CFBrCF2Br, whereas c-C3F5H reacts unselectively with I2 to produce a statistical 2:1 mixture of ICF2CF2CFHI:ICF2CFHCF2I. Tri- and di(pentafluorocyclopropyl) derivatives 2 also undergo ring-opening reaction with halogens to give 16 and 17. Upon treatment of tetrafluorocyclopropanes 1j, 1k, and 1l with Br2 or I2, ring opening occurred exclusively at substituted carbons to give XCF2CF2CXY2. Thermolysis of the ring-opened product ICF2CF2CFIORF at 240 °C gave RFI and ICF2CF2COF in high yields.
- Yang, Zhen-Yu
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p. 4410 - 4416
(2007/10/03)
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- Kinetics of hexafluoropropylene oxide pyrolysis studied by gas-phase NMR. Kinetic measurements made easy
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Gas-phase NMR complemented with a high-temperature probe makes possible quantitative kinetic studies of homogeneous vapor-phase reactions with unprecedented ease, as demonstrated with a study of the thermal fragmentation of hexafluoropropylene oxide. The reaction follows strictly first-order kinetics, is unaffected by surface chemistry, and the resulting Arrhenius activation parameters compare well with those obtained by more laborious classical methods of gas-phase reaction kinetics. The fragmentation kinetics is also unaffected by the presence of oxygen. The profiles for the evolution of the final products in this case show very graphically that singlet difluorocarbene, one of the initial products of the fragmentation of hexafluoropropylene oxide, does not react with oxygen, a ground-state triplet, at chemically significant rates.
- Krusic, Paul J.,Roe, D. Christopher,Smart, Bruce E.
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p. 117 - 123
(2007/10/03)
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- Preparation of halogenated compounds
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Halogenated compounds are prepared by ring opening reactions of highly fluorinated cyclopropanes with chlorine, bromine, iodine, or mixtures thereof at temperatures over 100° C. A novel compound, which is one type of compound produced, is a highly fluorinated and halogenated ether and other novel compounds are starting materials or products. The products of the process are useful as chain transfer agents for certain free radical polymerizations, and as chemical intermediates in the preparation of various products such as surfactants and textile surface treatments.
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- Kinetics of the self-reaction of CF2 radical and its reaction with H2, O2, CH4 and C2H4 over the temperature range 295-873 K
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Laser flash photolysis, coupled with time-resolved UV absorption detection, has been used to measure rate coefficients for the self-reaction of CF2 : CF2 + CF2 → C2F4 (1) and its reaction with the molecular species H2, O2, CH4 and C2H4 over the temperature range 295-873 K. The CF2 radicals were produced by the 193 nm laser photolysis of C2F4. At room temperature, values of k1 = (4.01 ± 0.51) × 10-14 cm3 molecule-1 s-1 were obtained for the rate coefficient of reaction (1) and σ249 = (1.61 ± 0.21) × 10-17 cm2 molecule-1 for the absorption cross-section of CF2 at 249 nm, where the spectral resolution was 0.5 nm (FWHM). The value of k1 is in good agreement with previous room-temperature measurements, but the value of σ249 is almost a factor of two lower, reflecting the lower spectral resolution used in this study. The absorption cross-section, σ249, was found to decrease with increasing temperature, whereas the rate coefficient, k1, exhibits a positive temperature dependence. The temperature dependence of k1 at 760 Torr N2, when combined with earlier shock-tube determinations at 1200 and 1400 K, could be fitted to a modified Arrhenius expression: k1 = (1.39 ± 0.20) × 10-19 T2 exp[(347 ± 56)/T] cm3 molecule-1 s-1 for the temperature range 295-1400 K. The uncertainties refer to random error in the parameters at the 95% confidence level. Systematic errors are estimated to be ± 10%. However, the variation of k1 with pressure at 873 K indicated that the reaction had not quite reached its high-pressure limit at 760 Torr, so this expression can only be regarded as an empirical expression for the temperature dependence at atmospheric pressure. At lower temperatures, k1 had clearly reached its high-pressure limiting value at 760 Torr. No evidence could be found at any temperature for products other than C2F4, implying that recombination is the only channel occurring. No reaction was observed between CF2 and any of the molecular reagents studied at temperatures up to 873 K. Upper limits were derived for the rate coefficient of CF2 with each reagent at several temperatures. At 873 K, the values are (in units of cm3 molecule-1 s-1) -19 for H2, -17 for O2, -19 for CH4 and -16 for C2H4. Experiments performed using the 193 nm photolysis of C3F6 as a source of CF2 suggested another reactive and absorbing species is generated in rather higher yield than CF2, at variance with earlier studies. The results could be rationalised by assuming the species to be C2F3 which reacts with CF2 with a rate coefficient estimated to be ca. 2 × 10-13 cm3 molecule-1 s-1 at 295 K. The implications of the very low reactivity of CF2 with molecular species, compared with its reactivity with radical species, O, H and OH, are discussed in the context of the role played by the CF2 radical in the chemistry of flame inhibition by fluorinated hydrocarbons considered as potential halon replacements.
- Battin-Leclerc, Frederique,Smith, Allan P.,Hayman, Garry D.,Murrells, Timothy P.
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p. 3305 - 3313
(2007/10/03)
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- Difluorocarbene insertion into Si-H bonds: the preparation and properties of difluoromethylsilanes
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Difluorocarbene, CF2, generated by thermal decomposition of CF3SiF3 at 100 deg C, has been found to insert into the Si-H bonds of halosilanes SiH3X (X = F, Cl, Br, I), methylhalosilanes CH3SiH2X (X = Br, Cl) and (CH3)2SiHCl, and disiloxane (SiH3)2O.Use of excess of the CF2-source CF3SiF3 and of pressure favour the formation of the di-insertion products (CHF2)2SiHX and (CHF2)2(CH3)SiX. (CHF2)3SiCl was identified among the products formed in the co-thermolysis of CF3SiF3 and (CHF2)SiH2Cl.In contrast, organosilanes RnSiH4-n (R = Me, Ph; n = 0-4), dihalosilanes SiH2X2 and RSiHX2, trihalosilanes HSiX3 and tetrahalosilanes SiX4 do not react with CF2 under these conditions.The reactivity and selectivity of difluorocarbene is discussed in terms of steric and electronic parameters.A kinetic deuterium effect, k(SiH)/k(SiD) 1.14, has been observed for the insertion into MeSiH2Cl.The mostly novel products were characterized by vibrational and multinuclear NMR spectroscopy.Difluoromethylsilane, (CHF2)SiH3, has been obtained from (CHF2)SiH2Cl and LiAlH4 in almost quantitative yield, and its vibrational spectrum has been recorded and interpreted with the assistance of a normal coordinate analysis.
- Buerger, H.,Eujen, R.,Moritz, P.
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p. 249 - 260
(2007/10/02)
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- Thermolysis of trifluoromethylsilanes. Novel fluoromethylsilanes by insertion of CF2 and CHF into Si-H bonds
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The thermal decomposition in the gas phase of CF3SiH3 and (CF3)2SiH2 begins at ca. 200 and ca. 100 deg C, respectively.It is catalyzed by KF, and involves as initial step a clean CF2 elimination with an α-fluorine shift.Reactive species such as HBr trap CF2 quantitatively (to give in this case CHF2Br), while addition to the less reactive cyclohexene (to give 7,7-difluorobicycloheptane) is accompanied by secondary reactions.These dominate in the absence of an efficient CF2 trapping agent, and spectroscopic product analyses reveal that they mainly arise from insertion of the carbenes CHnF(2-n) into Si-H bonds followed by CH(n+1)F(1-n) elimination (n = 0, 1).This sequence corresponds to H/F exchange at the Si atom.Insertion of CF2 (generated by thermolysis of CF3SiF3 below 100 deg C) into an Si-H bond of H3SiF to give CHF2SiH2F in good yield is the first example of such a reaction and demonstrates its usefulness for the selective synthesis of CHF2Si compounds.In addition, some dismutation of SiHnF(3-n) moieties accompanies the carbene elimination/insertion reactions and the resulting novel fluoromethylsilanes were characterized by 1H and 19F NMR and (in part) IR spectroscopy.The synthesis of (CF3)2SiHBr by cleavage of (CF3)2Si(H)N(i-Pr)2 with BBr3 and its conversion with LiAlH4 to (CF3)2SiH2 are reported.The mechanism of the CF2/SiH insertion reaction is discussed.
- Beckers, H.,Buerger, H.
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p. 207 - 219
(2007/10/02)
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- An Azidopiperideine -> Dihydrodiazepine Ring Expansion of the Fluorocarbon Class: Synthesis of Perfluoro-(1,4-dimethyl-2,3-diazacyclohepta-1,3-diene) via Thermolysis of Perfluoro-(6-azido-2,6-dimethyl-1-azacyclohexene)
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Flow pyrolysis of perfluoro-(6-azido-2,6-dimethyl-1-azacyclohexene) at ca. 380 deg C and 1 mmHg yields perfluoro-(1,4-dimethyl-2,3-diazacyclohepta-1,3-diene) (mainly) plus its isomers perfluoro-(1,5-dimethyl-6,7-diazabicyclohept-6-ene) and perfluoro-(2,4-dimethyl-1,3-diazacyclohepta-1,3-diene); the molecular geometry of the first of these products has been determined by gas-phase electron diffraction methods.
- Abed-Rabboh, Mohammad,Banks, Ronald E.,Beagley, Brian
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p. 1117 - 1118
(2007/10/02)
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- Energetics of the Rearrangement of Neutral and Ionized Perfluorocyclopropane to Perfluoropropylene. Use of Infrared Multiphoton Dissociation Spectra To Identify Structural Isomers of Molecular Ions
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Infrared photodissociation spectroscopy is used to compare the structure of gas-phase C3F6+ ions obtained by electron-impact ionization of two isomeric precursors: perfluoropropylene and perfluorocyclopropane.Photodissociation spectra are obtained by observing the extent of multiphoton dissociation as the CO2 laser is tuned across the 925-1080 cm-1 wavelength range.Ions are formed, stored, and detected with the use of techniques of ion cyclotron resonance spectroscopy.Infrared multiphoton exitation is effected by using low-power, continuous-wave laser radiation.The "fingerprint" spectrum of the molecular ion of pefluorocyclopropane is identical with that obtained from perfluoropropylidene, indicating rearrangement of the former to the latter.Photodissociation kinetics indicate that the entire perfluorocyclopropane molecular ion population isomerizes to the more stable perfluoropropylene structure.Thermochemistry of C3F6 and C3F6+ isomers is discussed.Comparisons are made with the analogous C3H6 system.Photoionization mass spectroscopy results yield ΔHf(c-C3F6) = -233.8 kcal/mol.
- Bomse, D. S.,Berman, D. Wayne,Beauchamp, J. L.
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p. 3967 - 3971
(2007/10/02)
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- Cyclopropane Chemistry. Part 4. The Reactions of 1,2,2-Trifluoroethylidene with Alkenes and Pyrolysis of the Resulting Cyclopropanes
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1,2,2-Trifluoroethylidene, generated by the pyrolysis of (1,1,2,2-tetrafluoroethyl)trifluorosilane, reacts with tetrafluoroethylene, ethylene, and a series of methyl-substituted ethylenes to give the corresponding 1-fluoro-1-difluoromethylcyclopropanes in good yield; cyclohexene gives the corresponding norcarane, and tris(trifluoromethyl)phosphine gives the corresponding phosphorane (CF3)3P(+)-C(-)F-CHF2.Pyrolysis of 1,2,2,3,3-pentafluoro-1-difluoromethylcyclopropane affords difluorocarbene and 3H-pentafluoropropene, but pyrolysis of the methyl-substituted cyclopropanes results in the formation of dienes in high yield, e.g. the 1,4-dienes CHF=CF-CMeR-CMe=CH2 from the cyclopropanes (R = H or Me) or 1,3-dienes from the methyl-substituted cyclopropanes, e.g. --> CH2=CMe-C(CHF2)=CH2.In certain cases further dehydrofluorination of the 1,3-dienes affords trienes, e.g. --> CH2=CMe-C(=CHF)-CMe=CH2.
- Haszeldine, Robert N.,Rowland, Ronald,Speight, James G.,Tipping, Anthony E.
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p. 314 - 324
(2007/10/02)
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- CYCLOPROPANE CHEMISTRY. PART 5 . HEXAFLUOROCYCLOPROPANE AS A SOURCE OF DIFLUOROCARBENE
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Thermolysis of hexafluorocyclopropane in the presence of ethylene, propene, vinyl chloride, and vinyl bromide gives good yields of the corresponding 1,1-difluorocyclopropanes, formed by addition of difluorocarbene to the olefin.The tetrafluoroethylene formed dimerises to octafluorocyclobutane, co-dimerises with the olefin, or survives, depending on the reaction conditions.With allene, hexafluorocyclopropane gives 1-(difluoromethylene)cyclopropane, 2,2,3,3-tetrafluorospiropentane, and products derived from tetrafluoroethylene and allene.
- Birchall, J. Michael,Fields, Roy,Haszeldine, Robert N.,McLean, Reginald J.
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p. 487 - 496
(2007/10/02)
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- Silicon-substituted derivatives of trifluoro(trifluoromethyl)silane. Some chemistry of the silicon-iodine bond in a polyhalo system
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The fluoroiodosilane CF3SiF2I has been utilized to generate a series of compounds of formula CF3SiF2X, where X = Br, Cl, F, and OSiF2CF3; all but X = F are new compounds. Conversion of Si-I bonds to Si-X is effected by antimony(III) halides or, for oxygen, mercury(II) oxide. Each of the halodifluoro(trifluoromethyl)silanes undergoes pyrolytic decomposition at 100° to generate SiF3X and CF2, although the thermal decomposition of CF3SiF2I is quite complex. Each of the CF3SiF2X species (other than CF3SiF3) reacts with water vapor to generate CF3SiF3 and, for X = Br or I, CF2HX. The halodifluoromethanes evidently result from the reaction of CF2 with HX - the CF2 in turn resulting from the interaction of water vapor and CF3SiF3 at room temperature. Correlations of fluorine chemical shifts and directly bonded silicon-fluorine coupling constants between CF3SiF2X species and the corresponding SiF3X species are presented.
- Sharp, Kenneth G.
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p. 1241 - 1244
(2008/10/08)
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- Perfluoro(alkylsilanes). II. Trifluoro(trifluoromethyl)silane and trifluoro(pentafluoroethyl)silane
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The perfluoro(alkylsilanes) CF3SiF3 (I) and C2F5SiF3 (II) have been prepared and characterized. Synthesis was effected by fluorination of the corresponding difluoroiodo(perfluoroalkyl)silanes, obtained by the reaction of SiF2 with the appropriate perfluoroalkyl iodide. Both compounds are stable at room temperature. Products from thermolysis of I at ca. 80° or above and of II at 160° or above, as pure compounds or in the presence of added reagents, are consistent with a decomposition mechanism involving α-fluorine transfer and the intermediacy of the carbenes : CF2 and CF3C?F, respectively. Basic and aqueous hydrolytic behaviors are described.
- Sharp,Coyle
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p. 1259 - 1264
(2007/10/12)
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- RAPID CONTINUOUS QUANTITATIVE ANALYSIS OF FLUOROCARBON MIXTURES WITH THE AID OF THE TIME-OF- FLIGHT MASS SPECTROMETER
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It is shown, with fluorocarbon mixtures as an example, that the time-of- flight mass spectrometer can be used for rapid continuous quantitative analysis of the products of gaseous reactions. The precision of the method is 8 to 10% for component contents of not less than 20%, and 15 to 18% for component contents below 10%. The sensitivity of the method is of the order of 1 vol. %. The precision and sensitivity achieved can be improved considerably by simple modification of the apparatus.
- DYMSHITS BM,KORETSKII YAP,LIR VI,TURKINA MYA,DOBYCHIN SL
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p. 2470 - 2475
(2008/10/08)
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