- Synthesis and vibrational spectroscopy of 1,1,2,2-tetrafluoroethane and its13C2 and d2 isotopomers
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The 13C2 and d2 isotopomers of 1,1,2,2-tetrafluoroethane (TFEA) have been synthesized. Raman spectra of these new species have been recorded, and infrared spectra of all three isotopomers, including some regions with high-resolution at -100°C, have also been recorded. Guided by recently published calculations of frequencies and infrared intensities and the new spectra, we have revised the previous assignments of fundamentals for the two rotamers of the normal species of TFEA. Assignments of the fundamentals for both rotamers of the 13C2 and d2 isotopomers are proposed. The anti rotamer is the more abundant species in the gas phase and, to a lesser extent, in the liquid phase and the only species in the crystal phase. Thus, the assignments of the anti rotamer of all three isotopic species are complete and supported by isotope product rules, but the assignments for the gauche rotamers are incomplete. Estimates of the missing frequencies for the gauche rotamer of the normal species are supplied.
- Craig, Norman C.,Chuang, Jessica I.,Nwofor, Christiana C.,Oertel, Catherine M.
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- Selective Copper Complex-Catalyzed Hydrodefluorination of Fluoroalkenes and Allyl Fluorides: A Tale of Two Mechanisms
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The transition to more economically friendly small-chain fluorinated groups is leading to a resurgence in the synthesis and reactivity of fluoroalkenes. One versatile method to obtain a variety of commercially relevant hydrofluoroalkenes involves the catalytic hydrodefluorination (HDF) of fluoroalkenes using silanes. In this work it is shown that copper hydride complexes of tertiary phosphorus ligands (L) can be tuned to achieve selective multiple HDF of fluoroalkenes. In one example, HDF of the hexafluoropropene dimer affords a single isomer of heptafluoro-2-methylpentene in which five fluorines have been selectively replaced with hydrogens. DFT computational studies suggest a distinct HDF mechanisms for L2CuH (bidentate or bulky monodentate phosphines) and L3CuH (small cone angle monodentate phosphines) catalysts, allowing for stereocontrol of the HDF of trifluoroethylene.
- Andrella, Nicholas O.,Xu, Nancy,Gabidullin, Bulat M.,Ehm, Christian,Baker, R. Tom
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supporting information
p. 11506 - 11521
(2019/08/20)
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- Copper-Catalyzed Difluoromethylation of Aryl Iodides with (Difluoromethyl)zinc Reagent
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The combination of difluoroiodomethane and zinc dust or diethylzinc can readily lead to (difluoromethyl)zinc reagents. Therefore, the first copper-catalyzed difluoromethylation of aryl iodides with the zinc reagents is accomplished to afford the difluorom
- Serizawa, Hiroki,Ishii, Koki,Aikawa, Kohsuke,Mikami, Koichi
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supporting information
p. 3686 - 3689
(2016/08/16)
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- Experimental and chemical kinetic study of the pyrolysis of trifluoroethane and the reaction of trifluoromethane with methane
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A detailed reaction mechanism is developed and used to model experimental data on the pyrolysis of CHF3 and the non-oxidative gas-phase reaction of CHF3 with CH4 in an alumina tube reactor at temperatures between 873 and 1173 K and at atmospheric pressure. It was found that CHF3 can be converted into C2F4 during pyrolysis and CH2=CF2 via reaction with CH4. Other products generated include C3F6, CH 2F2, C2H3F, C2HF 3, C2H6, C2H2 and CHF2CHF2. The rate of CHF3 decomposition can be expressed as 5.2×1013[s-1]e -295[kJmol-1]/RT. During the pyrolysis of CHF3 and in the reaction of CHF3 with CH4, the initial steps in the reaction involve the decomposition of CHF3 and subsequent formation of CF2 difluorocarbene radical and HF. It is proposed that CH4 is activated by a series of chain reactions, initiated by H radicals. The NIST HFC and GRI-Mech mechanisms, with minor modifications, are able to obtain satisfactory agreement between modelling results and experimental data. With these modelling analyses, the reactions leading to the formation of major and minor products are fully elucidated.
- Han, Wenfeng,Kennedy, Eric M.,Kundu, Sazal K.,MacKie, John C.,Adesina, Adesoji A.,Dlugogorski, Bogdan Z.
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scheme or table
p. 751 - 760
(2010/09/04)
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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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- The preparation of HCF2CdX and HCF2ZnX via direct insertion into the carbon halogen bond of CF2HY (Y = Br, I)
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The difluoromethylcadmium and zinc reagents have been prepared in DMF via direct insertion of Cd0 into the carbon halogen bond of CF2HY (Y = Br, I). These reagents are stable at 65-75 °C and exhibit prolonged stability and activity at room temperature. Metathesis of the difluoromethylcadmium reagents with Cu(I)X (X = Br, Cl) at -55 °C rapidly produces difluoromethylcopper. The copper reagent is significantly less stable than the cadmium or zinc reagent and rapidly decomposes at room temperature. The difluoromethylcadmium and copper reagents exhibit good reactivity with allylic halides, propargylic derivatives and 1-iodoalkynes to provide good yields of the corresponding difluoromethylalkenes, difluoromethylallenes and difluoromethyl-2-alkynes. Alkylation is successful only with reactive alkyl halides. Generally, the difluoromethylcopper reagent is more reactive than the difluoromethylcadmium reagent and generally exhibits higher regioselectivity in reactions that can occur by either α- or γ-attack.
- Burton, Donald J.,Hartgraves, Greg A.
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p. 1198 - 1215
(2008/02/08)
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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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- 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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- Pyrolyses of chlorodifluoromethane and trifluoromethane in the presence of hydrogen. Mechanism and optimization of reaction conditions
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When CHC1F2 and CHF3 are subjected to high-temperature, gas-phase flow pyrolysis in the presence of H2, they are converted, via a free radical chain mechanism, to CH2F2, CHF2CHF2, and CF3CH2F in good yield. Optimal conditions for pyrolysis of CHC1F2 involve a high conversion (92%) at 650 °C with an observed yield of products = 18, 17, and 28%, respectively, whereas optimal conditions for CHF3 involve a low conversion (24%) at 775 °C, but a higher yield of products (26, 6, and 39%, respectively).
- Romelaer,Kruger,Baker,Dolbier Jr.
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p. 6767 - 6772
(2007/10/03)
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- Gas-phase kinetics of the self reactions of the radicals CH2F and CHF2
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Fluorinated hydrocarbon radical-radical reactions in the gas phase have been studied at low pressure (0.5 ≤ p/mbar ≤ 2) and low temperature (253 ≤ T/K ≤ 333) using the discharge flow reactor molecular beam sampling mass spectrometry (MS) technique. Stable
- Beiderhase, Thomas,Hack, Walter,Hoyermann, Karlheinz,Olzmann, Matthias
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p. 625 - 641
(2007/10/03)
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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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- Selective reduction of halopolyfluorocarbons by organosilicon hydrides
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It is demonstrated that silicon hydrides can be used for reduction of polyfluorinated halocarbons. For example, the reaction between CF3CCl2F and excess triethylsilane, catalyzed by benzoyl peroxide, leads to the formation of a mixture containing CF3CHClF (major), CF3CH2F, and ClSi(C2H5)3. On the other hand, the reaction of chlorofluoroalkanes, containing an internal -CCl2- group readily proceeds with reduction of both chlorines, leading to compounds such as (CF3)2CH2 and CF3CH2C2F5. In contrast to chlorofluoroalkanes, bromofluoroalkanes are much more reactive and reaction with hydrosilane rapidly proceeds without the catalyst at elevated temperature.
- Petrov, Viacheslav A.
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p. 7294 - 7297
(2007/10/03)
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- Catalytic synthesis of 1,1,1,2-tetrafluoroethane from 1,1,1,2-tetrachloroethane - A mechanistic consideration
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1,1,1,2-Tetrachloroethane and its fluorinated derivatives as well as trichloroethene are fluorinated by hydrogen fluoride in the presence of a pre-conditioned chromia catalyst. The reaction pathways are derived under different conditions. Fluorinated haloalkanes are formed both by dehydrochlorination/hydrofruorination mechanism as well as chlorine/ fluorine exchange mechanism. Thus, beside fluorinated alkanes considerable amounts of haloolefins occur in the product mixture. A survey is given on the reaction pathway showing dependence on the reaction conditions. It is discussed with respect to calculated thermodynamic data. Kinetic and mechanistic investigations of the isomerisation reactions of 1.1.2.2-tetrafluoroethane on a CFC-conditioned chromia catalyst are also presented. The desired 1.1.1.2- tetrafluoroethane can be obtained from its symmetric isomer in the presence of a chromia catalyst conditioned exclusively with chlorine-free fluorocarbons. Mechanistic information is obtained by employing DCl which behaves similar to HF during the consecutive isomerisation reaction of 1.1.2.2- tetrafluoroethane. Thus, it is most probable that dehydrohalogenation/hydrohalogenation processes (elimination/addition mechanism) are mainly responsible for the formation of the haloolefins and halocarbons observed on chromia.
- Kemnitz,Niedersen,Kohne
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p. 485 - 493
(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 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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- FLUORINATION OF ETHYLENE BY HIGHER FLUORIDES OF COBALT, MANGANESE, AND CERIUM
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Fluorination of ethylene by higher fluorides of metals with variable valence (CoF3, CeF4, MnF3) is studied.Temperature dependence of the contents of fluorinated products are obtained.The mechanism of formation of significant amounts of 1,1,1,2-tetrafluoroethane in the reaction involving CoF3 and oligomers in the reaction involving CeF4, is proposed.
- Asovich, V. S.,Kornilov, V. V.,Maksimov, B. N.
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- Infrared Multiphoton Dissociation of Pentafluoroethane: Two-Channel Dissociation Process and Secondary Photolysis of Radical Products
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The dissociation yield and branching ratio in CO2 laser-induced multiphoton dissociation (MPD) of C2HF5 were investigated.In order to distinguish the two primary dissociation pathways (C2HF5 -> C2F4 + HF, Ea=71.6 kcal/mol; C2HF5 -> CF3 + CHF2, Ea=93.5 kcal/mol), Br2 was employed as an excellent scavenger of radicals and C2F4.The scavenged products were CBrF3, CHBrF2, CBr2F2, and C2Br2F4.The yield of C2Br2F4 originating from HF elimination was much smaller than those of CBrF3 and CHBrF2 from C-C bond rupture.The pulse energy dependence of the product distribution demonstrates that the primarily produced radicals were further photolyzed within the laser pulse (CF3 + nhν -> CF2 + F, and CHF2 + n'hν -> CF2 + H) to yield CBr2F2.The secondary photolysis of the radicals was also confirmed by real-time monitoring of infrared emission from HF* and DF* generated in the MPD of C2DF5 in the presence of H2 as an F atom scavenger.In the MPD of neat C2HF5, the formation of C2F4 was unexpectedly enhanced with increasing pulse energy; this was explained by assuming that C2F4 was mainly formed via recombination of CF2 radicals originating from the secondary photolysis of primarily produced radicals.
- Kato, Shuji,Makide, Yoshihiro,Takeuchi, Kazuo,Tominaga, Takeshi
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p. 3977 - 3981
(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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- HYDROGENOLYSIS OF DICHLOROTETRAFLUOROETHANE ISOMERIC MIXTURES FOR THE FORMATION OF 1,1,1,2-TETRAFLUOROETHANE
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1,1,1,2-tetrafluoroethane was prepared from isomeric mixtures of dichlorotetrafluoroethanes through selective hydrogenolysis of CF3-CCl2F catalyzed by Pd/C.The other isomer CClF2-CClF2 appeared more stable to hydrogenolysis and was only converted partially to the monohydrogenated derivative CHF2-CClF2.The influences of the three most important operating parameters were defined on the basis of a statistical testing program.The mathematical elaboration of the experimental data allowed definition of the relationships by which it is possible to foresee conversion of CF3-CCl2F, yield of CF3-CH2F and concentration of reaction products, such as CF3-CH3, CF3-CH2F, CF3-CHClF and CClF2-CHF2 in terms of the above parameters.
- Gervasutti, C.,Marangoni, L.,Marra, W.
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