- Kinetc Study of Infrared Multiphoton Dissociation. Two-Frequency Irradiation of CF3(13)COCF3 molecules at Natural Abundance
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The characteristics of the infrared multiphoton excitation of hexafluoroacetone in region I and region II have been investigated by photolysis with two CO2 laser pulses.The sequenced pulses were at different frequencies and had different fluences so that effects arising in the two regions could be clearly separated.We have studied the isotopically selective dissociation of CF3(13)COCF3 molecules, present at their natural abundance, as a function of five parameters, the frequency of the dissociating second pulse, the fluence of both pulses, the substrate pressure, and the interpulse delay.The results give a picture of the kinetic behavior of vibrationally excited hexafluoroacetone molecules produced in the presence of strong infrared fields.
- Hackett, P. A.,Gauthier, M.,Nip, W. S.,Willis, C.
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Read Online
- Time-Resolved Tunable Diode Laser Detection of Products of the Infrared Multiphoton Dissociation of Hexafluoroacetone: A Line-Strength and Band-Strength Measurement for CF3
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This paper describes the time resolved detection of CF3, C2F6, and CO following the infrared multiphoton dissociation of hexafluoroacetone.The primary photolysis mechanism has been estalished as follows: (CF3)2CO -> 2CF3 + CO; 2CF3 -> C2F6.Determination of the CO and C2F6 formed in a single photolysis pulse leads to a measure of an infrared line strength and ν3 band strength for CF3.Quantification of the CF3 in this manner allows a study of its reaction kinetics.The reactions of CF3 with added O2 and NO were found to have third-body rate constants of (2.1 +/- 0.5) * 10-29 and (2.8 +/- 0.7) * 10-29 cm6 molecule-2 s-1, respectively, at room temperature in the presence of 600 mTorr of hexafluoroacetone.
- Orlando, J. J.,Smith, D. R.
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Read Online
- Intensity and Pressure Effects in Infrared Multiphoton Dissociation. Phitilysis of Hexafluoroacetone and Trifluoromethyl Bromide with 2-ns Laser Pulses
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We have carried out a study of the effect pulse length on the infrared multiphoton dissociation of hexafluoroacetone.A constant fluence of 1.8 J cm-2 was used, for both short-pulse (2-ns fwhm) and long-pulse (ca. 120 ns fwhm, 5-μs tail, gain swithed, self-mode-locked TEA CO2 laser) irradiation.The dissociation yields are very significantly different both in their magnitude and in their dependence on pressure of substrate of of added hexafluoroethane.At moderate pressures (>0.2 torr) collisional effects dominate the long-pulse irradiation.Possible explanations of these effects are discussed.A study of the isotopically selective dissociation of trifluoromethyl bromide revealed that, although the intensity is high, isotopic selectivity (α ca. 20) is retained.
- Hackett, P. A.,Malatesta, V.,Nip, W. S.,Willis, C.,Corkum, P. B.
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Read Online
- Photoinduced Sulfur-Nitrogen Bond Rotation and Thermal Nitrogen Inversion in Heterocumulene OSNSO
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An exotic ternary S, N, O heterocumulene OSNSO in syn-syn (A) and syn-anti (B) conformations has been generated in the gas phase through flash vacuum pyrolysis of CF3S(O)NSO at 700 K. Upon visible light irradiation (570 ± 20 or 532 nm), both A and B, isolated in cryogenic matrices (N2, Ne, Ar, and Kr, a higher-energy anti-anti conformer (C). The reverse conformational transformation occurs either through S=N bond rotation (C to A and B) under visible light irradiation (400 ± 20 nm) at 2.8 K or through thermal nitrogen inversion (C to A) in the temperature range of 20-30 K, for which an exceptionally low activation barrier of 1.18 ± 0.07 kcal mol-1 has been experimentally determined.
- Wu, Zhuang,Feng, Ruijuan,Xu, Jian,Lu, Yan,Lu, Bo,Yang, Tao,Frenking, Gernot,Trabelsi, Tarek,Francisco, Joseph S.,Zeng, Xiaoqing
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p. 1231 - 1234
(2018/02/09)
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- Decomposition characteristics of C5F10O/air mixture as substitutes for SF6 to reduce global warming
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Sulfur hexafluoride (SF6) is widely used in the power industry but is a serious greenhouse gas. Many researchers committed to achieving sustainable development of the power industry are finding alternatives to SF6 gas. C5F10O performs well in terms of environmental protection, insulation, and safety and is a potential environment-friendly alternative gas. In this paper, the insulation and decomposition characteristics of C5F10O/air gas mixture were examined using gas-insulation performance test platform, and decomposition products were detected by gas chromatography–mass spectrometry. The formation mechanism and distribution of C5F10O decomposition products were analyzed through reactive molecular dynamics method and density functional theory. The influence of air on the decomposition of C5F10O was also evaluated. Results showed that the decomposition of C5F10O/air gas mixture mainly produces CF3[rad], C3F7[rad], C4F7O[rad], CO, CF2[rad], CF[rad], F[rad] and CF4. The breakdown voltage of C5F10O/air gas mixture decreased slightly after repeated breakdown tests, and CF4, C2F6, C3F8, C3F6, C4F10, CF2O were detected. These results can serve as a reference for the systematic comprehension of the decomposition characteristics of C5F10O/air gas mixture and for related engineering applications.
- Li, Yi,Zhang, Xiaoxing,Xiao, Song,Chen, Qi,Wang, Dibo
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- Process for producing hexafluoroethane
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The invention discloses a hexafluoroethane production technology, and the purity of a hexafluoroethane product can reach more than 99.99% by two-stage separation and purification. The hexafluoroethane production technology simplifies a conventional technological process, saves equipment investment, makes the reaction smooth, and improves the production efficiency.
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Paragraph 0031-0035
(2017/02/09)
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- Preparation method of electronic grade hexafluoroethane
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The invention relates to a preparation method of electronic grade hexafluoroethane. The preparation method comprises the following steps: a hydrogen fluoride gas and a chloropentafluoroethane gas enter a reactor containing a novel catalyst, and undergo a reaction at 300-500 DEG C at an air speed of 1-5 BV/h to prepare crude hexafluoroethane, wherein a molar ratio of the hydrogen fluoride gas to the chloropentafluoroethane gas is 1-3:1; and the crude hexafluoroethane is rectified, the rectified hexafluoroethane enters an adsorption tower containing an adsorbent and is adsorbed to obtain the highly-pure hexafluoroethane product.
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Paragraph 0025-0028; 0032-0035; 0039-0042; 0045-0048; 0053
(2017/06/02)
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- A method of preparing hexafluoroethane at high temperature
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The invention relates to a method of preparing hexafluoroethane at high temperature and belongs to the technical field of fluorine chemical engineering. The method includes adding cobaltous fluoride into a reactor, controlling the temperature of the reactor to be 350-450 DEG C and pressure of the reactor to be 0.1-0.15 MPa, adding a gas mixture of nitrogen trifluoride and nitrogen and pentafluoroethane, with the gas space velocity in a cobaltous oxide bed layer being 0.2-5 /min, and discharging a reaction product from the reactor to obtain the hexafluoroethane. Raw materials used in the method are safe. The method is safe in operation, high in product yield and suitable for large-scale industrial production.
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Paragraph 0036; 0037; 0038
(2017/02/17)
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- Preparation of trifluoroiodomethane via vapour-phase catalytic reaction between pentafluoroethane and iodine
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A new route for preparing C33I has been developed via a reaction between C2HF5 and I2. The influence of reaction temperature and active components of the catalysts on the amount of C33I was investigated. The result suggests that the selectivity of the C33I can be controlled by reaction conditions and active component of catalyst. The process for the formation of C33I and by-products is also discussed.
- Mao, Aiqin,Wang, Hua,Tan, Linhua,Nin, Xiangyang,Pan, Renming
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p. 4640 - 4642
(2013/07/19)
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- Me3SiCF3/AgF/Cu - A new reagents combination for selective trifluoromethylation of various organic halides by trifluoromethylcopper, CuCF3
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An alternative copper halide-free route to obtain highly reactive trifluoromethylcopper species has been developed via the reaction of silver fluoride and trimethyl(trifluoromethyl)silane followed by a redox transmetallation with elemental copper. The composition of the reactive intermediate was investigated by means of UV/Vis/NIR, ESR, 19F NMR spectroscopy and ESI mass spectrometry. "Trifluoromethylcopper" prepared by the oxidative transmetallation route exhibits excellent reactivity and selectivity in substitutions of iodine or bromine bond to aromatic or heterocyclic compounds for trifluoromethyl groups without any additional catalyst.
- Kremlev, Mikhail M.,Mushta, Aleksej I.,Tyrra, Wieland,Yagupolskii, Yurii L.,Naumann, Dieter,M?ller, Angela
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body text
p. 67 - 71
(2012/03/10)
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- GASEOUS DIELECTRICS WITH LOW GLOBAL WARMING POTENTIALS
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A dielectric gaseous compound which exhibits the following properties: a boiling point in the range between about ?20° C. to about ?273° C.; non-ozone depleting; a GWP less than about 22,200; chemical stability, as measured by a negative standard enthalpy of formation (dHf0); a toxicity level such that when the dielectric gas leaks, the effective diluted concentration does not exceed its PEL; and a dielectric strength greater than air.
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- Unimolecular rate constant and threshold energy for the HF elimination from chemically activated CF3CHFCF3
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Combination of CF3CHF and CF3 radicals at room temperature generated chemically activated CF3CHFCF3 molecules with 95 ± 3 kcal/mol of internal energy that decompose by loss of HF, initially attached to adjacent carbons, with an experimental unimolecular rate constant of (4.5 ± 1.1) x 102 s-1. Density functional theory was used to model the unimolecular rate constant for HF elimination, kHF, to determine a threshold energy of 75 ± 2 kcal/mol.
- Duncan, Juliana R.,Roach, Michael S.,Stiles, Brooke Sibila,Holmes, Bert E.
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experimental part
p. 6996 - 7002
(2011/02/16)
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- Catalytic pyrolysis of CHF3 over activated carbon and activated carbon supported potassium catalyst
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The catalytic activity of activated carbon (AC) and activated carbon supported potassium for the decomposition of CHF3 was investigated at temperatures between 873 and 1173 K and at a space velocity of 4300 h -1. It is found that activated carbon supported potassium shows high and relatively stable activity during the pyrolysis of CHF3 under the conditions studied. Compared with the gas phase reaction, the conversion of CHF3 increases by up to 10 times between 873 and 1123 K, with the major products being C2F4 and C3F6. Selectivities as high as 55% to C2F4 and 35% to C 3F6 are achieved under optimum conditions. The main byproduct HF readily reacts with K2O in the catalyst, converting the catalyst from K2O/AC into KF/AC. Selectivity to the major products remains relatively constant following this transformation.
- Han, Wenfeng,Kennedy, Eric M.,Liu, Huazhang,Li, Ying,Adesina, Adesoji A.,MacKie, John C.,Dlugogorski, Bogdan Z.
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scheme or table
p. 698 - 703
(2010/09/12)
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- Depolymerization of Fluoropolymers
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A process for depolymerizing fluoropolymers includes continuously feeding a solid fluoropolymer, in particulate form, into a horizontal cylindrical first reaction zone. The fluoropolymer particles enter the first reaction zone at one end. Within the first reaction zone, a central axle from which protrudes at least one paddle, continuously rotates. The rotating paddle serves to advance the fluoropolymer particles along the reaction zone while agitating them. As the fluoropolymer particles pass along the reaction zone, they are subjected to an elevated temperature, thereby depolymerizing the fluoropolymer into a fluoro-containing compound-rich gas phase. A residual solids phase is withdrawn at the other end of the first reaction zone, as is the gas phase. Optionally, the gas phase is passed through a second reaction zone which is also at an elevated temperature. The gas phase is quenched, thereby to recover the fluoro-containing compounds as gaseous products.
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Page/Page column 4-5
(2009/06/27)
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- Isothermal pyrolysis of iodomethanes in gases
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The fact was established that the pyrolysis of gaseous iodomethanes RI yields methane and non traces of recombination products R2. A pyrolysis mechanism was proposed and rate constants of limiting stages of the pyrolysis of iodomethane, trideuteroiodomethane, and diiodomethane over the range of 500-1500 K were determined. Pleiades Publishing, Ltd., 2009.
- Skorobogatov,Khripun,Rebrova
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scheme or table
p. 2641 - 2651
(2010/06/14)
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- Investigation of CF2 carbene on the surface of activated charcoal in the synthesis of trifluoroiodomethane via vapor-phase catalytic reaction
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This paper investigates the synthetic mechanism of trifluoroiodomethane (CF3I) in the reaction of trifluoromethane and iodine via vapor-phase catalytic reaction. It is suggested that CF2 carbene is the key intermediate and is formed in the pyrolysis process of CHF3 at high temperature. However, in pyrolysis of CHF3 under activated charcoal (AC) existing conditions, no C2F4 was detected. H2 and 2-methyl-2-butene could not trap the CF2 carbene. When treating the remained compounds on the used AC with H2, CH4 is formed on the process. It is proposed that CF2 carbene combines with AC strongly and transfers into CF3 radical on heat. In addition, it is found that the AC is not only the catalyst supporter to form CF3I, but also a co-catalyst to promote the formation of CF2 carbene and CF3 radical.
- Yang, Guang-Cheng,Lei, Shi,Pan, Ren-Ming,Quan, Heng-Dao
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experimental part
p. 231 - 235
(2009/08/07)
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- PRODUCTION PROCESSES FOR MAKING 1,1,1,2,2,3-HEXAFLUOROPROPANE
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A process for making HFC-236cb is disclosed. The process comprises reacting TFE with HFC-32 in the presence of at least one co-product and a suitable catalyst to produce a product mixture comprising HFC-236cb, wherein the total amount of the at least one co-product is at least 10 ppmv based on the total amount of the tetrafluoroethylene, the difluoromethane and the at least one co-product.
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Page/Page column 11-12
(2008/06/13)
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- CATALYTIC ADDITION OF HYDROFLUOROCARBONS TO FLUOROOLEFINS
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A process is disclosed for making RR1R2CCR1R2F wherein R is selected from the group consisting of CH3, CH2F, C2H4F, and F(CF2)nCH2CH2 where n is an integer from 1 to 10, each R1 is independently selected from the group consisting of H, Cl, F and CF3, and each R2 is independently selected from the group consisting of H, F and CF3. The process involves reacting RF with R1R2C=CR1R2 in the presence of SbF5 to produce a product mixture comprising RR1R2CCR1R2F, wherein the reaction temperature is from about -60° C to about -10° C, provided that total number of carbon atoms in R1R2C=CR1R2 is 5 or less.
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Page/Page column 10-11
(2008/06/13)
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- Perfluoroethanesulfonyl fluoride: Preparation from sultone
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A procedure was developed for preparing perfluoroethanesulfonyl fluoride by synthesis of hexafluoropropane-2-β-sultone from sulfuric anhydride and perfluoropropene, followed by hydrolysis of the sultone to α- tetrafluoroethanesulfonyl fluoride and fluorination of the latter with elemental fluorine.
- Nurgalieva,Bispen,Il'in,Moldavskii,Rozhkova
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p. 1562 - 1565
(2008/03/18)
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- Fluorination reactor
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Fluorination reactions in which an organic compound to be fluorinated is contacted with elemental fluorine and HF is produced as a byproduct are disclosed, wherein the elemental fluorine is contacted with the organic compound in the presence of a fluoride-adsorbing composition so that the amount of HF or another hydrogen-containing byproduct is reduced or eliminated. Reactor embodiments for the fluorination reactions are also disclosed.
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Page/Page column 3
(2008/06/13)
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- Synthesis of perfluoroalkanes in high-temperature fluorination of graphite with fluorine in a reactor with a free-falling graphite bed
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Reaction between fluorine and graphite in a reactor with a free-falling bed of graphite was studied in relation to the temperature in the reaction zone, ratio of the feeding rates of fluorine and graphite, and dilution of fluorine with an inert gas. Pleiades Publishing, Inc., 2006.
- Shelopin,Pashkevich,Alekseev,Mukhortov,Petrov,Asovich
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p. 1031 - 1034
(2008/02/05)
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- The kinetics of the CF3 + CF3 and CF3 + F combination reactions at 290 K and at He-pressures of ≈ 1-6 Torr
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The rate constants for the combination reactions CF3 + CF 3 and CF3 + F at 290 K and helium pressures of ≈ 1-6 Torr have been determined, using clean chemical sources of CF3, by means of discharge flow-molecular beam sampling-threshold ionisation mass spectrometry (DF/MB-TIMS). For the mutual reaction of CF3, no pressure dependence could be observed over the 1-6 Torr pressure range, indicating that the obtained rate constant of k1∞ = (1.8 ± 0.6) × 10-12 cm3 s-1 is the high pressure limit. This result, which agrees with the lowest values in literature but is ca. five times smaller than the most recent data, is fully in line with the known trend in the mutual reaction rate constant for the series CH3; CH2F; and CHF2. The reaction of CF 3 with F was found to exhibit a clear pressure dependence in the 0.5 to 6 Torr range. Using a Troe fall-off formalism, the low-pressure limit rate constant was determined as k20(He) = (1.47 ± 0.24) × 10-28 cm6 s-1 differing substantially from the only available previous determination; a variational transition state theoretical treatment is shown to support our data. The Owner Societies 2005.
- Dils, Bart,Vertommen, Johan,Carl, Shaun Avondale,Vereecken, Luc,Peeters, Jozef
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p. 1187 - 1193
(2007/10/03)
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- PROCESS FOR PRODUCTION OF 1,1,1,2-TETRAFLUOROETHANE AND/OR PENTAFLUOROETHANE AND APPLICATIONS OF THE SAME
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A process for producing high purity 1,1,1,2-tetrafluoroethane and/or pentafluoroethane by the step of purifying a crude product obtained by reacting trichloroethylene and/or tetrachloroethylene with hydrogen fluoride comprised of a main product including 1,1,1,2-tetrafluoroethane and/or pentafluoroethane, hydrogen fluoride as an azeotropic component with the main product, and impurity ingredients including at least an unsaturated compound, wherein said purifying step includes a step of bringing a mixture obtained by newly adding hydrogen fluoride into said crude product into contact with a fluorination catalyst in the vapor phase to reducing the content of the unsaturated compound contained in said crude product and a distillation step.
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Page/Page column 10-16
(2008/06/13)
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- Production and use of hexafluoroethane
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A process for production of high-purity hexafluoroethane, wherein a mixed gas containing hexafluoroethane and chlorotrifluoromethane is reacted with hydrogen fluoride in a gas phase in the presence of a fluorination catalyst at 200-450° C., for fluorination of the chlorotrifluoromethane, or wherein pentafluoroethane containing chlorine compounds with 1-3 carbon atoms is reacted with hydrogen in a gas phase in the presence of a hydrogenation catalyst at 150-400° C., and the product is then reacted with fluorine in a gas phase in the presence of a diluent gas.
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- Synthesis of perfluoroalkanes by high-temperature reaction of graphite with fluorine in a fluidized bed
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Synthesis of lower perfluoroalkanes (tetrafluoromethane, hexafluoroethane, octafluoropropane, decafluorobutane) by high-temperature reaction of graphite with fluorine in a fluidized bed was studied.
- Pashkevich,Shelopin,Mukhortov,Petrov,Alekseev,Asovich
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p. 1847 - 1853
(2007/10/03)
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- Surface Chemistry and Radiation Chemistry of Trifluoroiodomethane (CF 3I) on Mo(110)
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The surface-induced and electron-induced chemistry of trifluoroiodomethane (CF3I), a potential replacement for chlorofluorocarbons (CFCs) and chlorofluorobromocarbons (halons), were investigated under ultrahigh vacuum conditions (p a?? 1 a?? 10-10 Torr) on Mo(110). Results of temperature-programmed desorption (TPD) experiments indicate that dissociative adsorption of CF3I leads only to nonselective decomposition on Mo(110), in contrast to reactions of CF3I on other metal surfaces. Desorption of CF3 radicals and atomic iodine was detected mass spectrometrically during low-energy (10-100 eV) electron irradiation of four monolayer thick films of CF3I condensed at 100 K. Results of postirradiation temperature-programmed desorption experiments were used to identify CF2I2, C2F5I, C 2F6, C2F4I2, and CFI3 as electron-induced reaction products of CF3I. Except for CFI 3, all of these electron-induced reaction products of CF3I have been previously identified in ?3-radiolysis studies, supporting our earlier claim that temperature-programmed desorption experiments conducted following low-energy electron irradiation of multilayer thin films provide an effective method to investigate the effects of high-energy radiation, including radical-radical reactions.
- Nakayama, Nozomi,Ferrenz, Elizabeth E.,Ostling, Denise R.,Nichols, Andrea S.,Faulk, Janelle F.,Arumainayagam, Christopher R.
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p. 4080 - 4085
(2007/10/03)
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- Carbon-chain isomerization during the electrochemical fluorination in anhydrous hydrogen fluoride - A mechanistic study
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The compounds i-C4H9SO2F, i-C3H7SO2F and cyclo-C3 H7C(O)F have been subjected to electrochemical fluorination in anhydrous hydrogen fluoride. The resulting products were fully analyzed by NMR spectroscopy. From the reaction balances, literature data and quantum chemical calculations, a new mechanism for carbon-chain isomerization during the electrochemical fluorination (ECF) is proposed. The key step in the formation of isomeric products is believed to be a ring closure reaction involving carbo-cationic or biradical intermediates.
- Ignat'ev, Nikolai V.,Welz-Biermann, Urs,Heider, Udo,Kucheryna, Andriy,von Ahsen, Stefan,Habel, Wolfgang,Sartori, Peter,Willner, Helge
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- The gas-phase reaction of the CF3 radical with thiophene
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The reaction of CF3 radicals, generated by photolysis of CF 3I or hexafluoroacetone with thiophene, was studied in the gas phase at 25°C. At conversion of thiophene less than 20%, monosubstituted CF 3-thiophenes were found as the main reaction products, in addition to CF3H, C2F6, and monosubstituted dihydro-CF3-thiophene, the latter in very low proportion. An isomeric mixture of 2- and 3-CF3-thiophene was obtained in a ratio of about 16, independent of the radical source used (CF3I or hexafluoroacetone) to produce the CF3 radicals. A plausible mechanism that accounts for the observed products is proposed, and the reactivity of thiophene toward the CF3 radical at 25°C was determined as kadd/kc1/2 = 106 ± 4 cm3/2 mol-1/2 s-1/2.
- Herrera, Olga S.,Nieto, Jorge D.,Lane, Silvia I.,Oexler, Elena V.
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p. 1477 - 1481
(2007/10/03)
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- The radiation chemistry of acyclic hydrofluoro and perhalogenated ether and hydrocarbon compounds
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The radiolytic stability of some hydrofluoroethers and hydrofluorocarbons was investigated and compared with those of perfluoropolyethers (PFPEs) and the CCl2FCClF2 (CFC 113). The experimental results indicate that stability depends mainly on the relative abundance of hydrogen atoms in the molecule; however, a significant role is played also by the chemical structure (i.e. the relative positions of the hydrogen atoms in the molecule). As a result, molecules containing hydrogen atoms as -OCF2H chain ends show a higher stability compared with the other hydrofluoro compounds. Based on the analysis of the end products and on the nature of radicals detected by EPR, radiolysis mechanisms are proposed and discussed. Due to their high dipole moments the hydrofluoro compounds and CCl2FCClF2 degrade mainly through an ionic mechanism.
- Marchionni, Giuseppe,Guarda,Buttafava,Faucitano, Antonio
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p. 153 - 162
(2007/10/03)
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- Electrochemical fluorination of unsaturated sulfides and sulfones
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Electrochemical fluorination of some unsaturated sulfides and sulfones and their reactions with anhydrous HF were studied.
- Grigor'eva,Shainyan,Kaurova,Gracheva,Lesnevskaya,Barabanov
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p. 1095 - 1100
(2007/10/03)
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- An evaluation of the kinetic data for hydrogen abstraction from germanes in the gas phase by CF3 and C2F5 radicals
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After the review of kinetic data for reaction of hydrogen abstraction from germanoorganic compounds by trifluoromethyl and pentafluoroethyl radicals in the gas phase it was possible to determine the relative kinetic reactivity of the two radicals under consideration. The contributing factors are the thermochemical effects of the investigated reactions, steric hindrance derived mainly from the size of substrate molecules and the polar interaction between the polarized germane molecules and the radicals of different electrophilicity. The polar effects occurring in these radical reactions contribute primarily to the activation energy, but they have no significant contribution to the pre-exponential factor.
- Pieniazek
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p. 1739 - 1746
(2007/10/03)
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- Production of fluorinated ethanes using elemental fluorine
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Scientific principles of industrial gas-phase fluorination of fluoroethanes with elemental fluorine were developed. Conditions for fluorination of low-fluorinated ethanes without rupture of the C-C bond were determined.
- Pashkevich,Mukhortov,Alekseev,Asovich
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p. 1269 - 1274
(2007/10/03)
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- Gas-phase fluorination of fluoroethanes with elemental fluorine
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Scientific basis for industrial gas-phase fluorination of fluoroethanes with elemental fluorine allowing production of higher-fluorinated fluoroethanes from lower-fluorinated compounds is developed. 2001 MAIK "Nauka/Interperiodica".
- Pashkevich,Mukhortov,Alekseev,Asovich,Rozhdestvenskaya
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p. 1151 - 1155
(2007/10/03)
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- Experimental and computational studies on the gas-phase reaction of CBrF3 with hydrogen
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Gas-phase hydrogen dehalogenation of halon 1301 (bromotrifluoromethane, CBrF3) has been studied experimentally in a tubular alumina reactor operating at atmospheric pressure. It is found that hydrogen can accelerate the decomposition of halon 1301 and that conversion levels of CBrF3 and H2 increase with temperature and residence time. CBrF3 conversion increases with decreasing input volume ratio of CBrF3 to H2. The species produced are a complex mixture of halogenated hydrocarbons including CHF3, CH2F2, C2HF3, C2F6, C2H2F4, C2HF5, CHBrF2, CH3Br, CH2Br2, CHBr2F, and CH2BrF in addition to HBr and HF. The production yield of CHF3, the major product, increases with temperature to 1023 K, after which CHF3 levels decrease with increasing temperature. Conversely, CHF3 selectivity decreases with increasing temperature, residence time, or input ratio of CBrF3 to H2. The initiation reaction is believed to be the rupture of the C-Br bond in CBrF3, and the radical species CF3 then reacts with H2 to produce H and CHF3. The key step in the process is the attack of H radical on CBrF3 to produce CF3 and HBr. Experimental data are compared with the model predictions, and good agreement between experimental and modeling prediction is obtained for CHF3 production. However, the existing mechanism does not predict the formation of CHBrF2, which is detected during the experimental study, and the concentrations of CH2F2 and C2F6 measured experimentally are significantly different from those predicted. Modifications to the existing NIST mechanism are suggested to improve the prediction of the quantity of these species produced. Gas-phase hydrogen dehalogenation of halon 1301 (bromotrifluoromethane, CBrF3) has been studied experimentally in a tubular alumina reactor operating at atmospheric pressure. It is found that hydrogen can accelerate the decomposition of halon 1301 and that conversion levels of CBrF3 and H2 increase with temperature and residence time. CBrF3 conversion increases with decreasing input volume ratio of CBrF3 to H2. The species produced are a complex mixture of halogenated hydrocarbons including CHF3, CH2F2, C2HF3, C2F6, C2H2F4, C2HF5, CHBrF2, CH3Br, CH2Br2, CHBr2F, and CH2BrF in addition to HBr and HF. The production yield of CHF3, the major product, increases with temperature to 1023 K, after which CHF3 levels decrease with increasing temperature. Conversely, CHF3 selectivity decreases with increasing temperature, residence time, or input ratio of CBrF3 to H2. The initiation reaction is believed to be the rupture of the C-Br bond in CBrF3, and the radical species CF3 then reacts with H2 to produce H and CHF3. The key step in the process is the attack of H radical on CBrF3 to produce CF3 and HBr. Experimental data are compared with the model predictions, and good agreement between experimental and modeling prediction is obtained for CHF3 production. However, the existing mechanism does not predict the formation of CHBrF2, which is detected during the experimental study, and the concentrations of CH2F2 and C2F6 measured experimentally are significantly different from those predicted. Modifications to the existing NIST mechanism are suggested to improve the prediction of the quantity of these species produced.
- Li, Kai,Kennedy, Eric M.,Moghtaderi, Behdad,Dlugogorski, Bogdan Z.
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p. 584 - 590
(2007/10/03)
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- Electrochemical fluorination of aliphatic secondary amines
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Electrochemical fluorination (ECF) has been examined for six aliphatic secondary amines: N,N-di-ethylamine, N-ethyl,N-n-propylamine, N,N-di-n-propylamine, N-ethyl,N-iso-propylamine, N,N-di-iso-propylamine, and N-methyl,N-n-butylamine. It was found from these amines that not only the corresponding F-(N-fluoro-N,N-dialkylamines) but also F-imines having the same number of the carbon atoms were formed in low yields. The suppression of the C-N bond cleavage (blocking effect) which is expected to occur during fluorination due to the presence of bulky N-alkyl group was not observed as a result of the ECF of these aliphatic secondary amines. It was also found that the change of the initial solute concentration of N,N-di-n-propylamine did not affect on the product yields, which is usually observed for cyclic secondary amines. Several F-(N-fluoro-N,N-dialkylamines) were treated with triphenylphosphine for conversion into the corresponding F-imines. An imine bond was generated during this defluorination exclusively at the site of the alkyl group with a longer chain length when there were two different alkyl groups present in F-(N-fluoro-dialkylamines).
- Abe, Takashi,Hayashi, Eiji,Baba, Hajime
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- Technology for the preparation of perfluoro-organic compounds
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Fluorination by elemental fluorine of fluorine-containing alkenes, alkanes, ethers and tertiary amines was investigated, aimed at obtaining the perfluorinated analogs. The factors affecting yield of the target compounds were studied. Elements of technology were elucidated.
- Moldavskii, Dmitrii D.,Bispen, Tatjana A.,Kaurova, Galina I.,Furin, Georgii G.
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p. 157 - 167
(2007/10/03)
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- Shock-Tube Study of the Pyrolysis of the Halon Replacement Molecule CF3CHFCF3
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The kinetics of pyrolysis of CF3CHFCF3 have been studied in dilute mixtures (0.5 and 3 mol percent) in argon in a single-pulse shock tube over the temperature range of 1200-1500 K, residence times behind the reflected shock of between 650 and 850 μs, and pressures between 16 and 18 atm. Fluorinated products were quantified with gas chromatography and Fourier transform infrared spectroscopy; identification of unknown fluorocarbons and hydrofluorocarbons was performed with gas chromatography-mass spectrometry. The most significant products detected were C2F6, CF2=CHF, C2F4, C3F6, cyclo-C3F6, and CF3CHFCF2H. Traces of CF3H, CF4, C2F5H, C3F8, C4F6, and isomers of C4F8 were also identified. A detailed kinetic reaction scheme is presented to model the experimental reactant and product yield profiles as a function of temperature. The results of modeling showed that the major initiation reaction was the C-C bond fission reaction. The abstraction of the secondary H atom by F atoms was also predicted to be important, whereas 1,2-HF elimination was slower. From experiments and modeling, the following initiation rate constants were obtained: CF3CHFCF3 -> CF3 + CF3CHF (k37 = 1E15.9 exp(-355.6 kJ mol-1/RT) s-1), CF3CHFCF3 -> C3F6 + HF (k38 = 1E12.9 exp(-291.2 kJ mol-1/RT) s-1), and CF3CHFCF3 + F -> CF3CFCF3 + HF (k39 = 1E136 exp(-10.1 kJ mol-1/RT) cm3 mol-1 s-1).
- Hyenes, Robert G.,Mackie, John C.,Masri, Assaad R.
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- Formation of CF3O- in the gas phase
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We report experimental studies of the formation of CF3O- by ion-molecule and electron attachment reactions, and theoretical investigations of the structure and energetics of CF3O- and its neutral counterpart CF3O. The anion CF3O- is formed from the rapid attachment of free electrons to its neutral dimer, (CF3O)2. Potential sources of CF3O- through ion-molecule reactions of CF3- and F- were surveyed. CF3O- is formed in the bimolecular ion-molecule reaction of CF3- with SO2 and the third-order association reaction of F- with CF2O. In addition, rate constants for the reactions of CF3- with a variety of neutral compounds were measured. A number of cases were found in which formation of CF3O- was energetically allowed but was not observed. The potential energy surfaces of CF3O and CF3O- have been investigated using a variety of density functional theory (DFT) techniques. The ground-state minimum energy structure of CF3O was found to be a 2A′ Jahn-Teller distorted Cs-symmetry structure, while for the anion the ground state is 1A1 with a C3v-symmetry minimum. A search for other low-energy minima for CF3O- was unsuccessful. The DFT methods support a value for the adiabatic electron affinity of CF3O near 4.1 eV.
- Morris, Robert A.
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p. 8436 - 8442
(2007/10/03)
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- Threshold energies and unimolecular rate constants for elimination of HF from chemically activated CF3CH2CH3 and CF3CH2CF3: Effect of CH3 and CF3 substituents at the β-carbon and implications about the transition state
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Chemically activated CF3CH2CF3 was prepared with 104 kcal/mol of internal energy by the combination of CF3CH2 and CF3 radicals, and chemically activated CF3CH2CH3 was prepared with 101 and 95 kcal/mol by combination of CF3 and CH2CH3 radicals and by combination of CF3CH2 and CH3 radicals, respectively. The experimental rate constants for unimolecular 1,2-dehydrofluorination were 1.2 × 105 s-1 for CF3CH2CF3 and 3.2 × 106 s-1 for CF3CH2CH3 with 95 kcal/mol and 2.0 × 107 s-1 with 101 kcal/mol of energy. Fitting the calculated rate constants for HF elimination from RRKM theory to the experimental values provided threshold energies, E0, of 73 kcal/mol for CF3CH2CF3 and 62 kcal/mol for CF3CH2CH3. Comparing these threshold energies to those for CF3CH3 and CF3CH2Cl illustrates that replacing the hydrogen of CF3CH3 with CH3 lowers the E0 by 6 kcal/mol and replacing with CF3 or Cl raises the E0 by 5 and 8 kcal/mol, respectively. The CF3 substituent, an electron acceptor, increases the E0 an amount similar to Cl, suggesting that chlorine substituents also prefer to withdraw electron density from the β-carbon. As the HF transition state forms, it appears that electron density flows from the departing hydrogen to the β-carbon and from the β to the α-carbon, to the α-carbon from its substituents, but the α-carbon releases most of the incoming electron density to the departing fluorine. The present work supports this scenario because electron-donating substituents, such as CH3, on either carbon would reduce the E0 as they aid the flow of negative charge, while electron-withdrawing substituents such as Cl, F, and CF3 would raise the E0 for HF elimination because they hinder the flow of electron density.
- Ferguson, Heather A.,Ferguson, John D.,Holmes, Bert E.
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p. 5393 - 5397
(2007/10/03)
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- Production of perfluorinated organic compounds
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Fluorination of a series of perfluoroolefins and their alkoxy and diethylamino derivatives with elemental fluorine in the gas and liquid phases was studied. The possibility of fluorinating these compounds with pure fluorine was demonstrated. The fluorination parameters were determined, and separate stages of processes for preparing a series of practically important products were developed. The heats of fluorination of the compounds studied were calculated.
- Bispen,Moldavskii,Furin
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p. 1409 - 1417
(2007/10/03)
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- Synthesis of perfluorinated paraffins, esters, and tertiary amines by direct fluorination with elemental fluorine
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Fluorination of partially fluorinated olefins, paraffins, ethers, and tertiary amines with elemental fluorine at the gas-liquid interface under various conditions was studied.
- Bispen,Moldavskii
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p. 1009 - 1013
(2007/10/03)
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- Chlorine Abstraction Reaction from Chloroprentafluorobenzene by the CF3 Radical
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The temperature dependence of the rate constant for the gas phase abstraction reaction of chlorine by CFj from chloropentafluorobenzene was determined in the temperature range 573-653 K by the competitive method using the recombination of CF3 radicals as reference reaction. Taking a value of 1.53-1013 cm3 mor1 s-1 for the recombination rate constant, kc, = (6.76± 1.26) 1012 exp [-(6339±103) K/7] cm3 mor1 s-1. The Arrhcnius parameters were calculated by the Bond Strength-Bond Length method (BSBL) and good agreement was obtained with the experimental values. WILEY-VCH Verlag GmbH, 1998.
- Nieto,Herrera,Lane,Oexler
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p. 821 - 825
(2007/10/03)
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- One- and two-color infrared multiphoton dissociation of C3F6
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Multiphoton dissociation of C3F6 induced by one and two infrared laser beams is studied. The contribution of the different collisional processes to the yield is quantified using the recently extended McRae et al. model. It has been shown that the increase of the fluence in single irradiation and the change to the red of the second infrared pulse in double-beam experiments can have equivalent effects on the dissociation. These effects are an important increment in the yield and the extinction of the influence of the homogeneous collisions between C3F6 molecules on the process. In double-irradiation experiments, the introduction of time delays between the two laser pulses also leads to large enhancements of the dissociation, giving rise to two yield maxima when the delays are around 2 and 65 μs. A change in the final proportion of the dissociation products induced by modifying the frequency of the second pulse has been detected in the double-irradiation experiments.
- Torresano,Santos
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p. 2221 - 2228
(2007/10/03)
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- On the mechanism of the reaction of CF3 radicals with C6F5Cl in the temperature range 318-473 K
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The gas-phase reaction of CF3 radicals, generated by photolysis of perfluoroacetic anhydride, with C6F5Cl was studied in the temperature range 318-473 K and total pressures between 23 and 41 Torr. CF3 radicals react with C6F5Cl according to the following mechanism: CF3 + C6F5Cl ?kadd CF3C6F5Cl (1), (-1) CF3 + CF3C6F5Cl → CF3Cl + C6F5CF3 (2) 2CF3 →kc C2F6 (3) It was found that the addition reaction becomes reversible above 390 K. The addition rate parameters can be summarized in the following equation: log [(kadd/kc1/2)mol-1/2cm 3/2s-1/2] = (4.46±0.10)-(22.48±0.70)/θ where θ = 2.303 RTkJ mol-1 and kc is the recombination constant of CF3 radicals. A correlation between log(kadd/kc1/2) and the ionization potentials for 15 aromatic compounds was found. VCH Verlagsgesellschaft mbH, 1997.
- Nieto,Lane,Oexler
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p. 868 - 871
(2007/10/03)
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- The rate constant for the recombination of trifluoromethyl radicals at T = 296 K
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The high-pressure rate constant of the CF3 + CF3 → C2F6 reaction at T = 296 K was measured in the pulse photolysis (λ = 694.3 nm, ruby laser) of CF3NO in the presence of NO by means of the time-resolved detection of CF3NO by the intracavity absorption of He - Ne laser radiation (λ = 632.8 nm). The obtained value is k2x = (3.9 ± 1.3) × 10-12 cm3/s.
- Vakhtin
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p. 443 - 452
(2007/10/03)
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- Die elektrochemische fluorierung von alkansulfonamiden und alkandisulfonamiden
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Alkane sulphonylamides and disulphonylamides are stable in anhydrous (HF)x and undergo quantitative fission of S-N bonds during electrochemical fluorination. Besides NF3, the corresponding perfluoroalkane sulphonyl fluorides and disulphonyl fluorides are formed.
- Satori,Juenger
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- The dark reactions F2 + CF3I, C2F5I, and n-C3F7I
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The reactions between F2 and the lowest members of the homologous series of perfluoroalkyl iodides (CF3I, C2F5I, and n-C3F7I) have been studied. For these compounds, an exponential decrease
- Johnson,Walters,Dorko
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- Fluorinating Power and Selectivity of Potassium Hexafluoronickelate(III) as a Hydrocarbon Fluorinating Agent
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Fluorination of 1,1,1,2-tetrafluoroethane with potassium hexafluoronickelate(III) (K3) has been investigated.Fluorinating powers and selectivities of this reagent and cobalt trifluoride have been compared.
- Kostyaev, R. A.,Maksimov, B. N.
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p. 131 - 132
(2007/10/03)
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- INVESTIGATIONS IN THE REGION OF INDUSTRIAL FLUORINATED COMPOUNDS
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The synthesis and properties of ozone-friendly fluorohydrocarbons, fluoroolefins, and fluorinated compounds with functional groups (acids, alcohols, esters, and others), used for the creation of effective surfactants, ion-exchange membranes for various purposes, heat-resistant oils, and greases, were investigated.A technology was developed for the production of highly pure fluorinated compounds for microelectronics, fiber optics, and medicine.
- Maksimov, B. N.
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p. 1935 - 1940
(2007/10/03)
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- FLUORINATION OF ORGANIC COMPOUNDS IN THE PRESENCE OF HEXAFLUOROPROPYLENE OLIGOMERS
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Unsaturated perfluorinated compounds, polyfluorinated ethers, and aromatic and heterocyclic compounds were fluorinated by fluorine in the hexafluoropropylene trimer.A mechanism including the formation of the stable C9F19 radical is proposed.
- Zabolot-skikh, V. F.,Kochanov, A. S.,Tiunov, A. V.,Markin, I. V.
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p. 1282 - 1283
(2007/10/02)
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- FLUORINATION OF HYDROCARBONS BY THE HIGHER FLUORIDES OF COBALT, MANGANESE, AND CERIUM
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The fundamental possibility of producing partly fluorinated methanes, ethane, and propanes on an industrial scale was demonstrated with the higher fluorides of variable-valence metals as fluorinating agents.
- Asovich, V. S.,Kornilov, V. V.,Kostyaev, R. A.,Mel'nichenko, B. A.,Maruev, A. V.,Maksimov, B. N.
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p. 1284 - 1287
(2007/10/02)
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- DESORPTION OF REACTION PRODUCTS IN FLUORINATION OF ETHYLENE WITH COBALT TRIFLUORIDE
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Some macrokinetic relationships of ethylene fluorination with cobalt trifluoride have been investigated.Dependences of the degree of ethylene conversion on time of contact and temperature in reactors of batch and continuous operation have been studied.
- Kostyaev, R. A.,Pashkevich, D. S.
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p. 1426 - 1429
(2007/10/03)
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- OPTIMIZATION OF PHYSICOCHEMICAL PROPERTIES AND CONDITIONS OF PREPARATION OF CATALYSTS USED FOR THE SYNTHESIS OF FLUORINATED ORGANIC COMPOUNDS
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The physicochemical properties of magnesium fluoride and chromium-magnesium fluoride catalyst, and their activities in dehydrochlorination and fluorination of chlorinated aliphatic hydrocarbons have been studied as functions of preparation conditions.The optimal characteristics of the catalysts (Ssp, VΣ, Vmi, Vma, P) with respect to dehydrochlorination of tetrachloropropane and fluorination of trifluorotrichloroethane have been found.The dependence of the activities of MgF2 and CrF3/MgF2 on their porous structure has been revealed.The optimal technological parameters have been determined, which ensure preparation of magnesium fluoride and chromium-magnesium fluoride catalysts with required physicochemical properties.
- Kramerova, G. E.,Dul'tseva, Z. A.,Yurchenko, E. N.
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