- Cryoozonolysis of some perfluoroolefins and use of perfluoro ozonides as polymerization initiators
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Low-temperature (77-280 K) ozonolysis of perfluoro-4-methyl-2-pentene and perfluoro-2,4-dimethyl-3-ethyl-2-pentene by direct contact with ozone in the absence of solvents and oxygen was studied. The resulting perfluoro ozonides can be used as initiators o
- Kiryukhin,Barkalov,Ismoilov
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Read Online
- The Reaction of Vanadium Pentafluoride with Phosphorus Oxytrifluoride and with Trifluoroacetic Acid
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Vanadium pentafluoride reacts via an oxygen exchange reaction with phosphorous oxytrifluoride to give VOF3 and PF5.The latter forms a weak 1:1 adduct.VF5 reacts with trifluoroacetic acid to form trifluoroacetyl fluoride and VOF3.Both reactions are indicative of the strength of the V=O bond and its influence on the course of the reactions of VF5 with oxygen containing materials.
- Fowler, Brian R.,Moss, Kenneth C.
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Read Online
- THE DIRECT FLUORINATION OF ACETONE
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A synthesis for hexafluoroacetone using elemental fluorine is reported.Previously hexafluoroacetone and other ketones have been difficult to prepare using fluorination based syntheses.
- Clark, Wayne D.,Lagow, Richard J.
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Read Online
- THE ELECTROCEHIMCAL FLUORINATION OF ACETYL FLUORIDE
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The electrochemical fluorination of acetyl fluoride in anhydrous hydrogen fluoride to produce trifluoroacetyl fluoride was investigated in a microprocessor-aided modified Simons' reactor.The product was recorvered in acetic as trifluoroacetic acid.The experiments were carried out at a controlled anodic potential using a Cu/CuF2 reference electrode.Product yields of 36-45percent, current efficiencies of 30 to 50percent and energy efficiencies of 11-23percent were obtained.Experimental results of this investigation are presented and discussed.
- Wasser, D. J.,Johnson, P. S.,Klink, F. W.,Kucera, F.,Liu, Chung-Chiun
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Read Online
- Atmospheric chemistry of CF3CF double bond CF2: Kinetics and mechanism of its reactions with OH radicals, Cl atoms, and ozone
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Smog chamber/FTIR techniques were used to study the OH radical, the Cl atom, and ozone initiated oxidation of CF3CF double bond CF2 in 700 Torr of air at 296 K. Relative rate methods were used to measure k(OH+CF3CF double bond CF2) = (2.4±0.3)×10-12 and k(Cl+CF3CF double bond CF2) = (2.7±0.3)×10-11; absolute techniques were used to derive an upper limit of k(O3+CF3CF double bond CF2)-21 cm3 molecule-1 s-1. OH radical and Cl atom-initiated atmospheric oxidation of CF3CF double bond F2 gives COF2 and CF3C(O)F in molar yields of 100%. The atmospheric lifetime of CF3CF double bond CF2 is approximately 9 days with degradation proceeding via reaction with OH radicals to give trifluoroacetic acid in a molar yield of 100%. Results are discussed with respect to previous measurements of k(OH+CF3CF double bond CF2) and k(O3+CF3CF double bond CF2) and the potential importance of CF3CF double bond CF2 as a source of trifluoroacetic acid.
- Mashino,Ninomiya,Kawasaki,Wallington,Hurley
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Read Online
- Perfluoroalkyl ether as well as preparation and application thereof
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The invention relates to perfluoroalkyl ether as well as a preparation method and application thereof, wherein the preparation method specifically comprises the steps: taking perfluoroalkyl acyl fluoride and fluorinated metal salt as raw materials, and carrying out a reaction with a halogenated alkane substrate in the presence of a halogenated metal catalyst to obtain a target product perfluoroalkyl ether compound. Compared with the prior art, the method has the advantages that the synthesis process is simple and green, excellent selectivity and high yield are achieved, meanwhile, the perfluoroalkoxylation reagent and raw materials are cheap and easy to obtain, reaction conditions are mild, operation is easy, cost is low, popularization is easy, and the method is suitable for mass production; in addition, the method provided by the invention can be used for conveniently and efficiently preparing a plurality of novel alkoxy silanes of perfluoropolyether which can be applied to anti-fingerprint coatings.
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Paragraph 0054-0058
(2020/12/15)
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- Trifluoromethyl Benzoate: A Versatile Trifluoromethoxylation Reagent
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Trifluoromethyl benzoate (TFBz) is developed as a new shelf-stable trifluoromethoxylation reagent, which can be easily prepared from inexpensive starting materials using KF as the only fluorine source. The synthetic potency of TFBz is demonstrated by trifluoromethoxylation-halogenation of arynes, nucleophilic substitution of alkyl (pseudo)halides, cross-coupling with aryl stannanes, and asymmetric difunctionalization of alkenes. The unprecedented trifluoromethoxylation-halogenation of arynes proceeds smoothly at room temperature with the aid of a crown ether-complexed potassium cation, which significantly stabilizes the trifluoromethoxide anion derived from TFBz.
- Zhou, Min,Ni, Chuanfa,Zeng, Yuwen,Hu, Jinbo
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supporting information
p. 6801 - 6805
(2018/05/31)
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- Perfluoroacetyl fluoride and preparation method thereof
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The invention belongs to the technical field of fluorine fine chemical industry, and particularly relates to perfluoroacetyl fluoride and a preparation method thereof. The preparation method is as follows: trifluoroacetic anhydride is used as a material, and under the actions of alkali metal fluoride and organic alkali, a reaction is performed in an aprotic solvent to obtain the perfluoroacetyl fluoride. In the preparation process of the perfluoroacetyl fluoride, the trifluoroacetic anhydride is used as a starting reactant, and under the actions of catalysts, high-value chemical intermediate perfluoroacetyl fluoride is produced; the product yield is high, the raw material cost is low, the reaction condition is mild, the reaction process is simple in operation, the purification process is simple, the product purity is 99% or higher, and large-scale industrial production is easy.
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Paragraph 0019; 0020; 0021; 0022
(2017/07/22)
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- Shock wave studies of the pyrolysis of fluorocarbon oxygenates. I. The thermal dissociation of C3F6O and CF3COF
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The thermal decomposition of hexafluoropropylene oxide, C3F6O, to perfluoroacetyl fluoride, CF3COF, and CF2 has been studied in shock waves highly diluted in Ar between 630 and 1000 K. The measured rate constant k1 = 1.1 × 1014exp(-162(±4) kJ mol-1/RT) s-1 agrees well with literature data and modelling results. Using the reaction as a precursor, equimolar mixtures of CF3COF and CF2 were further heated. Combining experimental observations with theoretical modelling (on the CBS-QB3 and G4MP2 ab initio composite levels), CF3COF is shown to dissociate on two channels, either leading to CF2 + COF2 or to CF3 + FCO. By monitoring the CF2 signals, the branching ratio was determined between 1400 and 1900 K. The high pressure rate constants for the two channels were obtained from theoretical modelling as k5,∞(CF3COF → CF2 + COF2) = 7.1 × 1014exp(-320 kJ mol-1/RT) s-1 and k6,∞(CF3COF → CF3 + FCO) = 3.9 × 1015exp(-355 kJ mol-1/RT) s-1. The experimental results obtained at [Ar] ≈ 5 × 10-6 mol cm-3 were consistent with modelling results, showing that the reaction is in the falloff range of the unimolecular dissociation. The mechanism of secondary reactions following CF3COF dissociation has been analysed as well.
- Cobos,Hintzer,S?lter,Tellbach,Thaler,Troe
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p. 3151 - 3158
(2017/08/17)
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- Atmospheric chemistry of CF3CF2CHO: Absorption cross sections in the UV and IR regions, photolysis at 308 nm, and gas-phase reaction with OH radicals (T = 263-358 K)
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The relative importance in the atmosphere of UV photolysis of perfluoropropionaldehyde, CF3CF2CHO, and reaction with hydroxyl (OH) radicals has been investigated in this work. First, the forbidden n → π* transition of the carbonyl chromophore was characterized between 230 and 380 nm as a function of temperature (269-298 K) and UV absorption cross sections, σλ, were determined in those ranges. In addition, IR absorption cross sections were determined between 4000 and 500 cm-1. Pulsed laser photolysis (PLP) of CF3CF 2CHO coupled to Fourier transform infrared (FTIR) was employed to determine the overall photolysis quantum yield, Φλ, at 308 nm and 298 K. Φλ=308 nm was pressure dependent, ranging from (0.94 ± 0.14) at 75 Torr to (0.30 ± 0.01) at 760 Torr. This dependence is characterized by the Stern-Volmer parameters Φλ=308 nm0 = (1.19 ± 0.34) and KSV = (1.22 ± 0.52) × 10-19 cm3 molecule-1. End products of the photodissociation of CF3CF2CHO were measured and quantified by FTIR spectroscopy. Furthermore, the rate coefficients for the OH + CF3CF2CHO reaction, k1, were determined as a function of temperature (T = 263-358 K) by PLP-LIF. At room temperature the rate coefficient is k1(T = 298 K) = (5.57 ± 0.07) × 10 -13 cm3 molecule-1 s-1, whereas the temperature dependence is described by k1(T) = (2.56 ± 0.32) × 10-12 exp{-(458 ± 36)/T} cm3 molecule -1 s-1. On the basis of our results, photolysis of CF 3CF2CHO in the actinic region could be an important removal process for CF3CF2CHO in the atmosphere. The formation of the primary products in the UV photolysis of CF3CF 2CHO is also discussed.
- Antinolo, Maria,Jimenez, Elena,Gonzalez, Sergio,Albaladejo, Jose
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p. 178 - 186
(2014/02/14)
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- Catalytic synthesis of certain perfluorinated ketones and study of their structure by 19F NMR spectroscopy
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An efficient catalyst of a perfluorinated ketone synthesis of a high selectivity in the absence of solvent was proposed. Products of reaction of perfluorinated fluorides of various structures with tetrafluoroethylene and hexafluoropropylene in the presence of efficient catalysts without solvent were examined. The structure of the resulting products and their isomeric composition were identified by 19F NMR spectrscopy. Pleiades Publishing, Ltd., 2013.
- Fenichev,Berenblit,Bispen,Lebedev,Moldavskii
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p. 1243 - 1251
(2014/02/14)
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- Reduction of fluorinated cyclopropene by nitrogenase
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Reduction of the first known halogen-containing substrate by nitrogenase (N2ase), 3,3-difluorocyclopropene (DFCP), was investigated. Reduction requires both N2ase proteins (MoFe and Fe protein), ATP, and an exogenous reductant (dithionite, DT), as with N2 and known alternative substrates of the enzyme. Two major products providing evidence for reductive C-F bond cleavage were confirmed, propene (P1, requiring 6e -/6H+) and 2-fluoropropene (P2, 4e-/4H +). Both were identified by GC-MS and NMR spectroscopy, and had the same Km constants (0.022 atm, 5.4 mM). Reduction of 1,2-dideuterated DFCP (d2-DFCP) further revealed that (i) in both P1 and P2, two deuterium atoms are retained, one on carbon-1 and one on carbon-3, indicating that C=C bond cleavage rather than C-C bond cleavage is involved during DFCP reduction at least to P2 (assuming no F migration); (ii) no selectivity was observed in formation of cis and trans isomers of 1,3-d2-2- fluoropropene, whereas cis-1,3-d2-propene is the predominant 1,3-d2-propene product, indicating that one of the bound reduction intermediates on the pathway to propene is constrained geometrically. A reduction mechanism, consistent with hydride transfer as a key step, is discussed. Reductive C-F bond cleavage is an ability of N2ase that further demonstrates the unique and remarkable scope of its catalytic prowess.
- Ni, Feng,Lee, Chi Chung,Hwang, Candy S.,Hu, Yilin,Ribbe, Markus W.,Mckenna, Charles E.
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supporting information
p. 10346 - 10352
(2013/08/23)
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- Synthesis and properties of trifluoromethoxyl fluoroformyl anhydride, CF3OC(O)OC(O)F
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In the present work the synthesis of the trifluoromethoxyl fluoroformyl anhydride is presented for the first time. Two strategies were employed to obtain CF3OC(O)OC(O)F: the thermal decomposition of CF 3OC(O)OOOC(O)F in excess of CO, and the reaction between CF 3OC(O)OOC(O)F, FC(O)OOC(O)F and CO. A mechanism was proposed taking into account reaction rates and thermal stability of the intermediates. DFT calculations at B3LYP/6-311+G* level were used to explore the conformational space of this molecule and the relative populations of conformers at room temperature, and to simulate the experimental vibrational spectrum. This molecule completes the family of the asymmetric oxygen bonded acyl compounds CF3OC(O)OxC(O)F with x = 1-3.
- Manetti, Martín M.,Argüello, Gustavo A.,Paci, Maxi A. Burgos
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experimental part
p. 16 - 20
(2012/10/08)
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- Products formed at intermediate stages of electrochemical perfluorination of propionyl and n-butyryl chlorides. Further evidence in support of NiF 3 mediated free radical pathway
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The partially fluorinated HF soluble intermediates formed during the electrochemical perfluorination of propionyl chloride (PC) and n-butyryl chloride (n-BC) were analyzed after passing 0%, 25%, 50%, 75% and 100% of theoretical charge required for the fluorination of PC and n-BC. The acid fluorides formed were converted to their corresponding sodium salt by alkali treatment and were separated by methanol extraction. The methanol was subsequently removed from the extract by vacuum distillation and the residue containing partially fluorinated sodium carboxylates was analyzed using 19F and 1H NMR spectra. Initial perfluorination on activated electrode surface indicates the operation of 'zipper-mechanism'. Formation of partially fluorinated product mixture, initial selectivity towards primary and secondary carbon, carbon chain isomerization and formation of cleaved and coupled products support the general operation of free radical pathway in the overall electrochemical process.
- Rangarajan,Sathyamoorthi,Velayutham,Noel,Singh,Brahma, Raju
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experimental part
p. 107 - 113
(2011/03/23)
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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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- 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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- Thermal gas-phase reaction of perfluorobuta-1,3-diene with NO2
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The reaction of NO2 with perfluorobuta-1,3-diene, CF2{double bond, long}CFCF{double bond, long}CF2 (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 CF2{double bond, long}CFCF(NO2)CF2(NO2) (I), CF2(NO2)CF{double bond, long}CFCF2(NO2) (II), CF2{double bond, long}CFCF(NO2)C(O)F (III) and CF2(NO2)CF{double bond, long}CFC(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 -CF{double bond, long}CF2 group and the Raman spectrum shows a band located at 1733 cm-1, corresponding to -CF{double bond, long}CF- group. It indicates, that in this temperature range, NO2 attacks initially only one double bound of CF2{double bond, long}CFCF{double bond, long}CF2. Since the intermediate radical CF2{double bond, long}CFC{radical dot}FCF2(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.
- Czarnowski, Joanna
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p. 261 - 266
(2008/12/22)
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- Atmospheric chemistry of CF3CF{double bond, long}CH2: Products and mechanisms of Cl atom and OH radical initiated oxidation
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The products of Cl atom and OH radical initiated oxidation of CF3CF{double bond, long}CH2 were studied in 700 Torr of N2/O2 diluent at 296 ± 1 K. The reactions of Cl atoms and OH radicals with CF3CF{double bond, long}CH2 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 CF3CF{double bond, long}CH2 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 CF3CF{double bond, long}CH2 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 CF3CF{double bond, long}CH2.
- Hurley,Wallington,Javadi,Nielsen
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experimental part
p. 263 - 267
(2008/10/09)
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- Formation of perfluorobutene-2 epoxide in the thermal gas-phase reaction of perfluorobutene-2 with nitrogen dioxide. An experimental and DFT study
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The mechanism of the thermal reaction between perfluorobutene-2 and NO 2 in the gas phase has been investigated in the temperature range 418.5-470.0 K. At temperatures below 432 K, equal amounts of perfluorobutene-2 epoxide (PFBE) and NO are formed. At higher temperatures, PFBE decomposes generating CF3C(O)F and CF3CF biradicals. The latter self-recombine reforming the parent perfluorobutene-2 molecule. The addition of O2 does not affect the reaction course. This reaction system provides a new and promising method for PFBE preparation. Based on the perfluorobutene-2 consumption, PFBE yields larger than 90% were obtained. The energetics of the relevant reaction pathways has been calculated using various density functional theory methods. These calculations confirm the reaction mechanism based on experimental results. The computed vibrational spectra predicted for the PFBE at the B3LYP/6-311+G(3df) and B98/6-311+G(3df) levels of theory are in very good agreement with that obtained experimentally. by Oldenbourg Wissenschaftsverlag.
- Czarnowski,Cobos
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p. 1595 - 1608
(2008/02/12)
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- Synthesis of carbon-labeled perfluoroalkyl compounds
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Various 13C and 14C carbon labeled compounds Rf—bCF(U)y(T)z??Formula 1A or Rf—bCF2bCF(U)y(T)z??Formula 1B wherein Rf is a linear or branched perfluoroalkyl radical Z(CmF2m)—, m is 1, 3 to 20, or a mixture thereof; Z is F when m is 1, and Z is F, Cl, or H when m is 3 to 20 or a mixture thereof; b is 13 or 14; y is 1, and z is 0 or 1; and when y and z are each 1, U is F, and T is selected from the group consisting of monovalent radicals —X wherein X is I or Br, —CH2—CH2—X, —CH=CH2, —CH2—CH2—OH, —CH2—COOH, —CH2OH, —bCH2OH, —COOH, —bCOOH, —O—CF(CF3)—C(O)F, —O—CF(CF3)—X, —SO2Y wherein Y is H, F or Cl, and —SO3H; and when y is 1, and z is 0, U is selected from the group consisting of divalent radicals =CH—COOH, =CH—CH2—OH, and =O, are disclosed, and a process for their preparation which selectively introduces 13C and 14C carbon labels into a fluoroalkyl chain.
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Page/Page column 7
(2008/06/13)
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- Method of producing acid fluorides from acid chlorides
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Acid fluorides, for example carboxylic acid fluorides and sulfuryl fluoride are produced by reacting the corresponding acid chlorides with hydrogen fluoride adducts of ammonium fluoride or amine hydrofluorides (which act as a catalyst or as a fluorination agent). Consumed HF adducts may be regenerated with HF.
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Page column 7
(2008/06/13)
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- Kinetics study of the gas-phase reactions of C2F 5OC(O)H and n-C3F7OC(O)H with OH radicals at 253-328 K
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The rate constants, k1 and k2 for the reactions of C2F5OC(O)H and n-C3F7OC(O)H with OH radicals were measured using an FT-IR technique at 253-328 K. k1 and k2 were det
- Chen,Kutsuna,Tokuhashi,Sekiya
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p. 563 - 568
(2007/10/03)
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- Environmentally Benign Processes for Making Useful Fluorocarbons: Nickel- or Copper(I) Iodide-Catalyzed Reaction of Highly Fluorinated Epoxides with Halogens in the Absence of Solvent and Thermal Addition of CF2I 2 to Olefins
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Highly fluorinated epoxides react with halogens in the presence of nickel powder or CuI at elevated temperatures to provide a useful and general synthesis of dihalodifluoromethanes (CF2X2) and fluoroacyl fluorides (RFCOF) in the absence of solvent. At 185 °C, hexafluoropropylene oxide and halogens produce CF2X 2 (X = I, Br) in 68-90% isolated yields, along with small amounts of X(CF2)nX, (n = 2, 3). With interhalogens I-X (X = Cl, Br), a mixture of CF2I2, CF2XI, and CF 2X2 was obtained. The fluorinated epoxides substituted with perfluorophenyl, fluorosulfonyl, and chlorofluoroalkyl groups also react cleanly with iodine to give CF2I2 and the corresponding fluorinated acyl fluorides in good yields. The reaction probably involves an oxidative addition of fluorinated epoxides into metal surfaces to form an oxametallacycle, followed by rapid decomposition to difluorocarbene-metal surfaces, which alters the reactivity of the difluorocarbene carbon from electrophilic to nucleophilic. The increase of nucleophilicity of difluorocarbene facilitates the reaction with electrophilic halogens. CF 2I2 reacted with olefins thermally to give 1,3-diiodofluoropropane derivatives. Both fluorinated and nonfluorinated alkenes gave good yields of the adducts. Reaction with ethylene, propylene, perfluoroalkylethylene, vinylidene fluoride, and trifluoroethylene provided the corresponding adducts in 58-86% yields. With tetrafluoroethylene, a 1:1 adduct was predominantly formed along with small amounts of higher homologues. In contrast to perfluoroalkyl iodides, CF2I2 also readily adds to perfluorovinyl ethers to give 1,3-diiodoperfluoro ethers.
- Yang, Zhen-Yu
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p. 2394 - 2403
(2007/10/03)
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- Reaction of 1-hydrohexafluoroisobutenyloxytrimethylsilane with fluoride ion sources. 2,2,2′,2′-Tetrakis(trifluoromethyl)divinyl ether
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The reaction of 1-hydrohexafluoroisobutenyloxytrimethylsilane (2a) with cesium fluoride in diglyme leads to elimination of trimethylfluorosilane to form the 1-hydrohexafluoroisobutenolate anion (3), which is silylated with trialkylchlorosilanes at the oxygen atom. In the presence of bis(trifluoromethyl)ketene N,N,O-trimethylaminoacetal or N-(α,α- difluoroalkyl)-dialkylamines, silane 2a is transformed into 2,2,2′, 2′-tetrakis(trifluoromethyl)divinyl ether. The reaction of trifluoroacetic anhydride with N-(1,1,2,2-tetrafluoroethyl)diethylamine affords trifluoroacetyl fluoride in quantitative yield.
- Volkonskii,Kagramanova,Mysov,Mysova
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p. 2774 - 2781
(2007/10/03)
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- Kinetics and mechanism of the thermal gas-phase oxidation of perfluorobutene-2 in presence of trifluoromethyl hypofluorite
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The oxidation of perfluorobutene-2 (C4F8) initiated by trifluoromethyl hypofluorite (CF3OF) in presence of O2 has been studied at 323.1, 332.6, 342.5, and 352.0 K, using a conventional static system. The initial pressure of CF3OF was varied between 4.8 and 23.6 Torr, that of C4F8 between 48.7 and 302.4 Torr, and that of O2 between 51.5 and 270.4 Torr. Several runs were made in presence of 325.5-451.2 Torr of N2. The main products were COF2, CF3C(O)F, and CF3OC(O)F. Small amounts of compound containing -CF(CF3)-O-C(O)CF3 group were also formed, as detected by 13C NMR spectroscopy. The oxidation is a homogeneous short-chain reaction, attaining, at the pressure of O2 used, the pseudo-zero-order condition with respect to O2 as reactant. The reaction is independent of the total pressure. Its basic steps are as follows: the thermal generation of CF3O radicals by the abstraction of fluorine atom of CF3OF by C4F8, the addition of CF3O to the alkene, the formation of perfluoroalkoxy radicals RO in presence of O2, and the decomposition of these radicals via the C-C bond scission, giving products containing -C(O)F end group and reforming RO and CF3O radicals. The mechanism consistent with experimental results is postulated.
- Romano, Rosana M.,Della Vedova, Carlos O.,Czarnowski, Joanna
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p. 532 - 541
(2007/10/03)
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- Fluorinated olefins and oleum
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Oleum has some advantages over pure sulfur trioxide and may be successfully used for preparation of beta-sultones from hexafluoropropene, 2H-pentafluoropropene, 6H-perfluoro-1-hexene and perfluoro(propylvinyl) ether (VE). Depending on the reaction conditi
- Cheburkov, Yuri,Lamanna, William M.
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p. 147 - 152
(2007/10/03)
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- An experimental and modelling study of ignition delays in shock-heated ethane-oxygen-argon mixtures inhibited by 2H-heptafluoropropane
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Ignition delay times have been measured behind reflected shock waves in ethane-oxygenargon mixtures at temperatures between 1150 and 1500 K and pre-ignition pressures between 10 and 14 atm. Delay times have been measured both by pressure rise and OH absorption at 307 nm. Kinetic modelling of the ignition delays has been made using the GRIMech 3.0 mechanism which with addition of several reactions involving HO2 radicals and an increase in the barrier for reaction between C2H5 and O2 can satisfactorily model delays over the studied equivalence ratios of φ= 1.7 to 0.68. Addition of 2H-heptafluoropropane up to 13 mol % (of ethane) had little inhibition effect on stoichiometric ethane-oxygen-argon mixtures but inhibited ignition in a mixture of φ= 1.5. A kinetic mechanism is presented to model the inhibition process. by Oldenbourg Wissenschaftsverlag, Muenchen.
- Ikeda, Emi,Mackie, John C.
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p. 997 - 1009
(2007/10/03)
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- Viscosity effects on the thermal decomposition of bis(perfluoro-2-N-propoxypropionyl) peroxide in dense carbon dioxide and fluorinated solvents
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The thermal decomposition of the free-radical initiator bis(perfluoro-2-N-propoxyprionyl) peroxide (BPPP) was studied in dense carbon dioxide and a series of fluorinated solvents. For the fluorinated solvents, the observed first-order decomposition rate constants, kobs, increased with decreasing solvent viscosity, suggesting a single-bond decomposition mechanism. The kobs values are comparatively larger in dense carbon dioxide and similar to the zero-viscosity rate constants extrapolated from the decomposition kinetics in the fluorinated solvents. The decomposition activation parameters demonstrate a compensation behavior of the activation enthalpy with the activation entropy upon change in solvent viscosity. Comparison of the change in activation parameter values upon change in solvent viscosity for BPPP with two additional initiators, acetyl peroxide (AP) and trifluoroacetyl peroxide (TFAP), further suggests that carbon dioxide exerts a very minimal influence on the decomposition mechanism of these initiators through solvent-cage effects.
- Clayton Bunyard,Kadla,Desimone
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p. 7199 - 7206
(2007/10/03)
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- Kinetics and mechanism of thermal gas-phase oxidation of hexafluoropropene in the presence of trifluoromethylhypofluorite, CF3OF
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The oxidation of hexafluoropropene with molecular oxygen in the presence of CF3OF has been studied at 303.0, 313.0 and 323.4 K, using a conventional static system. The initial pressure of CF3OF was varied between 1.7 and 16.6 Torr, that of C3F6 between 10.0 and 120.2 Torr and that of O2 between 82.0 and 599.8 Torr. Several runs were made in the presence of 325.3-499.2 Torr of N2. Major products were COF2, CF3C(O)F, CF3OC(O)F and a new compound, CF3OCF2OCF2C(O)F. The latter was characterised by the determination of its relative molecular mass and its IR spectrum, which is consistent with the calculated one using theoretical approximations. Small amounts of CF3OCF2C(O)F were also formed. The oxidation is an homogeneous chain reaction, attaining, at the pressure of O2 used, the pseudo-zero-order condition with respect to O2 as a reactant. It is independent of the total pressure. The basic steps are: the thermal generation of CF3O radicals by abstraction of the fluorine atom from CF3OF by C3F6, chain initiation by the addition of CF3O to olefin leading, in the presence of O2, to the formation of haloalkoxy radicals, which decompose via the C-C scission to give products containing C(O)F group and CF3 radicals, reforming CF3O. The full mechanism is postulated.
- Dos Santos Afonso,Romano,Della Vedova,Czarnowski
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p. 1393 - 1399
(2007/10/03)
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- The reaction of C3F6 with dioxygen under IR laser initiation
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The mechanism of oxidation of C3F6 by molecular O2 under IR multiphoton excitation was studied. The activation energy of C3F6 oxidation was estimated from the dependence of the reagent conversion on the O2 pressure. The data obtained for the final reaction products, CF3CFO and CF2O, suggest the dioxetane mechanism of C3F6 oxidation.
- Kuricheva,Dunyakhin,Timofeev,Zhitnev
-
-
- Effect of temperature on low-temperature liquid-phase oxidation of hexafluoropropene by molecular oxygen
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The effect of temperature on the rate of consumption of hexafluoropropylene and the rates of formation of the products (perfluoropolyether polyperoxide, trifluoroacetyl fluoride, carbonyl fluoride, and hexafluoropropene oxide) over the temperature range 213-303 K at various oxygen pressures and a constant initiation rate was studied. The apparent activation energies were calculated.
- Shapovalov
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p. 1338 - 1340
(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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- Fluorine atom initiated oxidation of CF3CFH2 (HFC-134a) studied by FTIR spectroscopy
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Experiments have been carried out on the oxidation of CF3CFH2 (HFC-134a). Reaction was initiated by continuous photolysis of F2 in the near-ultraviolet. The F atoms produced abstracted a hydrogen atom from CF3CFH2 initiating oxidation in gas mixtures containing O2 and made up to a total pressure of 700 torr with N2. Product yields were measured using Fourier-transform infrared (FTIR) spectroscopy. Experiments were performed with several different partial pressures of O2 present, and at three temperatures; 298, 323, and 357 K. The major products were HC(O)F, CF3C(O)F, and CF3O3CF3, consistent with H atom abstraction by O2 and CC bond scission being the dominant loss processes for CF3CFHO radicals: CF3CFHO+O2→CF3C(O)F+HO2 (4a); CF3CFHO+M→CF3+HC(O)F+M (4b). The following expression was derived for the ratio of rate constants for these reactions: k4a/k4b = (3.8±1.6)×10-24 exp[(2400±500)/T]cm3 molecule-1 (viii). The main fate of the CF3 radicals was formation of CF3O3CF3 and small amounts of CF3OH were detected. The results of the present experiments in which F atoms were used to initiate reaction are in good agreement with those of previous studies in which Cl atoms were employed to initiate the oxidation of HFC-134a.
- Hasson,Moore,Smith
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p. 541 - 554
(2007/10/03)
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- The thermal decomposition of haloacetic acids: A laser pyrolysis and semiempirical study
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Infrared laser-powered homogeneous pyrolysis, coupled with Fourier-transform infrared measurement of product distributions, has demonstrated that four different unimolecular mechanisms are significant in the initiation of gas-phase thermal decomposition of CH3COOH (1), CF3COOH (2), CH2ClCOOH (3), CHCl2COOH (4), CCl3COOH (5), CH2BrCOOH (6), and CH2ICOOH (7): decarboxylation and dehydration for (1); H-X elimination for (2)-(6); and C-X bond homolysis for (6) and (7). These conclusions are supported by the semiempirical calculation of activation energies for the possible pathways.
- Hettema, Hinne,Hore, Nathan R.,Renner, Noel D.,Russell, Douglas K.
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p. 363 - 372
(2007/10/03)
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- Absolute rate constants for the self reactions of HO2, CF3CFHO2, and CF3O2 radicals and the cross reactions of HO2 with FO2, HO2 with CF3CFHO2, and HO2 with CF3O2 at 295 K
-
The kinetics of the self-reactions of HO2, CF3CFHO2, and CF3O2 radicals and the cross reactions of HO2 with FO2, HO2 with CF3CFHO2, and HO2 with CF3O2 radicals, were studied by pulse radiolysis combined with time resolved UV absorption spectroscopy at 295 K. The rate constants for these reactions were obtained by computer simulation of absorption transients monitored at 220, 230, and 240 nm. The following rate constants were obtained at 295 K and 1000 mbar total pressure of SF6 (unit: 10-12 cm3 molecule-1 s-1): k(HO2+HO2) = 3.5±1.0, k(CF3CFHO2+CF3CFHO2) = 3.5±0.8, k(CF3O2+CF3O2) = 2.25±0.30, k(HO2+FO2) = 9±4, k(CF3CFHO2+HO2) = 5.0±1.5, and k(CF3O2+HO2) = 4.0±2.0. In addition, the decomposition rate of CF3CFHO radicals was estimated to be (0.2-2)×103 s-1 in 1000 mbar of SF6. Results are discussed in the context of the atmospheric chemistry of hydrofluorocarbons.
- Sehested,Mogelberg,Fagerstrom,Mahmoud,Wallington
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p. 673 - 682
(2007/10/03)
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- Reaction Modulation Spectroscopy: A New Approach to Quantifying Reaction Mechanisms
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We report a new experimental method, reaction modulation spectroscopy, (RMS) that, shows great promise in enabling the systematic analysis of complicated oxidation mechanisms over the full range of atmospheric pressures and temperatures.The method is a form of difference spectroscopy in which we employ FTIR absorption spectroscopy in a high-pressure flow system (HPFS) where a plume of reacting species is examined before any significant fraction reaches the tube wall.The onest of the reaction is modulated by modulating the flow of an initiating radical species over a period that is short compared to any associated with experimental drifts.Spectra obtained with the radical source on and off are ratioed, giving a transmittance spectrum showing only the effects of the reaction modulation.The system is in a steady state, so signal averaging over long periods (up to several days) may be employed, if necessary, to obtain a high signal-to-noise ratio.Because no bulk reagents are disturbed in the process, we observe extremaly precise conservation of mass in the reaction plume.We illustrate the technique for the system OH + C3F6 (+O2, NOx,...) -> -> CF2O + CF3CFO, where we observe nearly 100percent conservatioin of odd-nitrogen species and roughly 90percent conservation of carbon under conditions chosen to force the reaction to completion, with residual spectra consistent with unidentified minor products having cross sections similar to the observed aldehydes.
- Donahue, Neil M.,Demerjian, Kenneth L.,Anderson, James G.
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p. 17855 - 17861
(2007/10/03)
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- Rate Mechanism of the Atmospheric Degradation of 1,1,1,2-Tetrafluoroethane (HFC-134a)
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Ihe atmospheric chemical behaviour of 1,1,1,2-tetrafluoroethane (CF3CFH2, HFC-134a) with respect to its rate and mechanism of degradation in the troposphere has been investigated. The rate coefficient for the reaction of (i a) CF3CFH2 +OH→CF3CFH + H2O has been determined in direct time-resolved experiments using iaser-pulse initiation and laser long-path absorption. A value of kia = (4.6±0.5)×10-15 cm3 A at T = 295K has been found. The ratio of the rate coefficients for the reactions of the CF3CFHO-radical with O2, (4) CF3CFHO + O2→CF3CFO + HO2, and C-C bond fission, (5) CF3CFHO + M→CFHO + CF3 + M, for T =295 K and ptotal = 50 mbar (O2) has been obtained to be k4/(k5 [M]) = 1.5×10-19 cm3, with the individual values being k4 = 2.7×10-15 cm3/s and k5 [M] = 1.8×104 s-1. The mechanism of the atmospheric degradation of HFC-134a has been investigated in the temperature range 244-295 K and ptotal = 1000 mbar using UV photolysis/FTIR product studies. From these experiments the Arrhenius expression k4/(k5 [M]) = 8.7 ×10-25 exp ((3240-610+990) K/T) cm3 was determined. Moreover, it is concluded that the major carbonyl products are CF3CFO, CFHO and CF2O which result from the two possible reactions of the oxy radical CF3CFHO. As a consequence the yield of these carbonyl products is dependent on temperature, O2 partial pressure and total pressure. For the reaction of CFHO with Cl atoms the Arrhenius expression k18 = 5.7×10-14 exp (-(1130 ±160)K/T)cm3/s was determined in the temperature range 244-298 K. VCH Verlagsgeseuschaft mbH, 1996.
- Bednarek,Ereil,Hoffmann,Kohlmann,Moers,Zellner
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p. 528 - 539
(2007/10/03)
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- Role of excited CF3CFHO radicals in the atmospheric chemistry of HFC-134a
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The atmospheric degradation of HFC-134a (CF3CFH2) proceeds via the formation of CF3CFHO radicals. Long path length FTIR environmental chamber techniques were used to study the atmospheric fate of CF3-CFHO radicals. Two competing reaction pathways were identified for CF3CFHO radicals: reaction with O2, CF3CFHO + O2 → CF3C(O)F + HO2, and decomposition via C-C bond scission, CF3CFHO + M → CF3 + HC(O)F + M. CF3CFHO radicals were produced by two different reactions: either via the self-reaction of CF3CFHO2 radicals or via the CF3CFHO2 + NO reaction. It was found that decomposition was much more important when CF3CFHO radicals were produced via the CF3CFHO2 + NO reaction than when they were produced via the self-reaction of CF3CFHO2 radicals. We ascribe this observation to the formation of vibrationally excited CF3CFHO* radicals in the CF3CFHO2 + NO reaction. Rapid decomposition of CF3-CFHO* radicals limits the formation of CF3C(O)F and hence CF3COOH in the atmospheric degradation of HFC-134a. We estimate that the CF3COOH yield from atmospheric oxidation of HFC-134a is 7-20%. Vibrationally excited alkoxy radicals may play an important role in the atmospheric chemistry of other organic compounds.
- Wallington,Hurley,Fracheboud,Orlando,Tyndall,Sehested,Mogelberg,Nielsen
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p. 18116 - 18122
(2007/10/03)
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- Regiospecific fluorination of the aryl group in C6F5I and the preparation of C6F7IF2 - The first perfluorovinyl iodine (III) compound
-
Pentafluoroiodobenzene was oxidized regiospecificly by IF5/BF3 in CH2C12 to 1-iodo-heptafluoro-1,4-cyclohexadiene. With bromo- and chloro-pentafluorobenzene as substrates, the addition of two fluorine atoms to the aromatic ring proceeded analogously but more slowly. 1-Iodo-heptafluoro-1,4-cyclohexadiene was converted to 1-difluoroiodo-heptafluoro-1,4-cyclohexadiene by low-temperature fluorination. The thermal stability and reactivity of the first example of a perfluorinated vinyl iodine(III) compound are reported.
- Frohn,Nielinger
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p. 143 - 146
(2007/10/03)
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- On the Possibility of the Formation of Carbonyl Compounds in Reactions Involving Peroxide Radicals
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It is shown that, for low-temperature liquid-phase oxidation of hexafluoropropene by molecular oxygen, the conventionally accepted mechanism of formation of carbonyl compounds, via the fragmentation of alkoxy radicals, is not confirmed experimentally; the most likely alternative is an anomalous reaction path involving a terminationless interaction of peroxide radicals.
- Shapovalov, V. V.,Poluektov, V. A.,Ryabinin, N. A.
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p. 552 - 555
(2007/10/02)
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- Decomposition of hexafluoropropynele oxide in a strong IR field
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Multiphoton dissociation (MPD) of hexafluoropropylene oxide (HFPO) under focused CO2-laser radiation was studied.A high-energy channel of HFPO decomposition was revealed.The dependences of the MPD yield and the ratio between various channels of HFPO decomposition on the laser radiation frequency in the range from 967.7 to 1090.0 cm-1, the incident radiation energy, and the initial pressure of HFPO were obtained.A considerable contribution of thermal decomposition of HFPO occurring outside of the irradiated zone to the total yield of its decomposition was established.An explanation for pressure dependence of the yield of HFPO decomposition was suggested. - Keywords: multiphoton dissociation; hexafluoropropylene oxide; carbenes; thermal decomposition; MPD spectrum.
- Dunyakhin, V. A.,Kuricheva, O. V.,Timofeev, V. V.,Zhitnev, Yu. N.
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p. 2079 - 2086
(2007/10/03)
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- Rate and Mechanism of the Atmospheric Degradation of 2H-Heptafluoropropane (HFC-227)
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The atmospheric chemical behaviour of 2H-Heptafluoropropane (CF3CHFCF3, HFC-227) with respect to its rate and mechanism of degradation in the troposphere has been investigated.The rate coefficient for the reaction of HFC-227 with OH radicals has been determined in direct time resolved experiments using a combination of laser-pulse initiation and LIF.In the temperature range T=298-463 K the Arrhenius expression k(T)=(3.8+/-0.8) 10-13 exp (-1596+/-77 K/T) cm3/s, which corresponds to k (298 K)=(1.8+/-0.3) 10-15 cm3/s, was found.The mechanism of the atmospheric degradation of HFC-227 has been investigated using both, laser-pulse initiated/time resolved and UV photolysis/FTIR product studies.It is concluded that the major carbonyl products are CF3COF and CF2O which result from the decomposition of the oxy radical CF3CF(O)CF3 by C-C bond fission.The rate coefficient for this decomposition process has been determined to be k=(2+/-1) 103 s-1 at 298 K.Based on the reactivity of HFC-227 with respect to the reaction with OH radicals, the atmospheric lifetime and the GWP value for HFC-227 are estimated to be -40 years and 0.6+/-0.2, respectively. Key Words: Atmospheric Chemistry / Chemical Kinetics / Radicals
- Zellner, R.,Bednarek, G.,Hoffmann, A.,Kohlmann, J.P.,Moers, V.,Saathoff, H.
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p. 141 - 146
(2007/10/02)
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- Atmospheric Chemistry of HFC-134a: Kinetic and Mechanistic Study of the CF3CFHO2 + HO2 Reaction
-
Rate constant measurements for the title reaction and for F + CF3CFH2 are reported over the 210-363 K temperature range.Reacting mixtures of CF3CFHO2 and HO2 radicals are created by the flash photolysis of F2 in the presence of HFC-134a (CF3CFH2), H2, and O2 and are probed by time-resolved UV absorption spectroscopy.The deconvolution of spectra taken at various delay times provides concentration versus time profiles for the respective radical species.A comparison of the initial CF3CFHO2 and HO2 concentrations yields a relative rate determination of k1 = (9.8+9-5) * 10-11e(-1130+/-190)/T cm3s-1 for the F + CF3CFH2 rate constant.A simultaneous fit of the radical decay curves to a mechanism containing the known HO2 self-reaction kinetics, the previously determined CF3CFHO2 self-reaction mechanism, and a cross reaction between these species yields a rate constant of k7 = (1.8+2.4-1.0) * 10-13e(910+/-220)/T cm3s-1 for the HO2 + CF3CFHO2 reaction.A product stucy at 296 K by Fourier transform infrared spectroscopy reveals that less than 5percent of the product appears as CF3C(O)F.By inference, >95percent of the reaction gives the hydroperoxide CF3CFHOOH.Implications of these results are discussed with respect to the atmospheric degradation of HFC-134a (CF3CFH2).
- Maricq, M. Matti,Szente, Joseph J.,Hurley, Michael D.,Wallington, Timothy J.
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p. 8962 - 8970
(2007/10/02)
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- Mechanism of Atmospheric Oxidation of 1,1,1,2-Tetrafluoroethane (HFC 134a)
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The chlorine-initiated photooxidation of hydrofluorocarbon 134a (CF3CH2F) has been studied in the temperature range 235-318 K and at 1 atm total pressure using UV absorption.Trifluoroacetyl fluoride and formyl fluoride were observed as the major products.IR analysis of the reaction mixture also showed carbonyl fluoride as a product.By measurement of the yields of HC(O)F from the photooxidation as a function of and temperature, the rate of the unimolecular decomposition of the oxy radical, CF3CHFO, reaction (5), was determined relative to its reaction with O2, reaction (4): CF3CHFO + O2 --> CF3C(O)F + HO2 (4), CF3CHFO --> CF3 + HC(O)F (5).The results were treated using both an arithmetic derivation and numerical integration with a detailed reaction scheme.Inclusion of other recently published kinetic data leads to the following recommended rate expression for reaction (5) at 1 atm k5 = 7.4E11exp s-1.The errors are 1?.The observation of enhanced product yields in the present work is attributed to the reaction of the CF3O radical with HFC 134a leading to further peroxy radical formation.The results have been incorporated into a 2D atmospheric model to assess the environmental implications of HFC 134a release in the troposphere.
- Rattigan, Oliver V.,Rowley, David M.,Wild, Oliver,Jones, Roderic L.,Cox, R. Anthony
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p. 1819 - 1830
(2007/10/02)
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- Synthesis of functionalized polyfluoroalkyl hypochlorites and fluoroxy compounds and their reactions with some fluoroalkenes
-
Several new polyfluoroalkyl hypochlorites and fluoroxy compounds containing Cl, H and Br in the alkyl group have been prepared and characterized by 19F NMR, 1H NMR and IR spectroscopies and by their reactions with fluoroalkenes to produce new polyfluoroethers.The novel compounds are prepared by the CsF-catalyzed addition of F2 or ClF to the C=O bond in CF3C(O)CF2Cl, ClCF2C(O)CF2Cl, and their derivatives HCF2C(O)CF3 and HCF2C(O)CF2Cl.Compounds containing an α-CF3 group exhibit enhanced thermal stability.New fluoroxy compounds and hypochlorites have also been prepared from the acid fluorides CF3-CFX-C(O)F (X = Cl, Br), which are obtained by the ring-opening reaction of hexafluoropropene oxide with (CH3)3SiCl, LiBr and (C2H5)3SiBr.These -OX compounds behave similarly to previously known materials with two α-F atoms, decomposing quickly at room temperature to COF2 and haloalkanes.
- Randolph, Bruce B.,DesMarteau, Darryl D.
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p. 129 - 150
(2007/10/02)
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- Atmospheric Chemistry of CF3O Radicals: Reaction with H2O
-
Evidence is presented that CF3O radicals react with H2O in the gas phase at 296 K to give CF3OH and OH radicals.This reaction is calculated to be exothermic by 1.7 kcal mol-1 implying a surprisingly strong CF3O-H bond energy of 120 +/- 3 kcal mol-1.Results from a relative rate experimental study suggest that the rate constant for the reaction of CF3O radicals with H2O lies in the range (0.2-40) x 10-17 cm3 molecule-1 s-1.Implications for the atmospheric chemistry of CF3O radicals are discussed.
- Wallington, Timothy J.,Hurley, Michael D.,Schneider, William F.,Sehested, Jens,Nielsen, Ole John
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p. 7606 - 7611
(2007/10/02)
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- Synthesis of Pentafluoroethyl Trifluoroacetate by Low-Temperature Direct Fluorination
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Ethyl acetate was perfluorinated by direct fluorination in the presence of cesium fluoride, affroding pentafluoroethyl trifluoroacetate in excellent yield.In the reaction pathway, the dimerization of trifluoroacetyl fluoride with cesium fluoride gives pentafluoroethyl trifluoroacetate.
- Akimura, Takashi,Shibakami, Motonari,Tamura, Masanori,Kurosawa, Shigeru,Sekiya, Akira
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p. 2454 - 2456
(2007/10/02)
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- Flash Photolysis-Time-Resolved UV Spectroscopy of the CF3CFHO2 Self-Reaction
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The self-reaction of CF3CFHO2 has been studied via time-resolved ultraviolet spectroscopy over the temperature range 211-372 K.The absorption spectrum of CF3CFHO2 extends from 190 to 275 nm with a maximum cross section of (5.2 +/- 0.3) * 10-18 cm2 molecule-1 at 213 nm.The UV absorbance of the reaction mixture decreases and shifts to the blue as the reaction progresses.This is consistent with the CF3CFHO2 self-reaction producing CF3CFHO, the alkoxy radical then decomposing to yield CF3, which adds molecular oxygen to form CF3O2.The CF3CFHO2 self-reaction has a negative temperature dependence with rate constant given by k1 = (7.8 +/- 1.3) * 10-13 e(605+/-40)/T cm3 s-1.The rate of alkoxy radical dissociation, at 230 Torr of total pressure, is k2a = (3.7 +/- 0.7) * 107 e-(2200+/-150)/T s-1.The rate constants for CF3O2 reaction with CF3CFHO2 and itself are determined to be k8 = (8 +/- 3) * 10-12 and k9 = (1.8 +/- 0.5) * 10-12 cm3 s-1, respectively, at 297 K.
- Maricq, M. Matti,Szente, Joseph J.
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p. 10862 - 10868
(2007/10/02)
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- MASS SPECTROMETRY STUDY OF THE PYROLYSIS OF PERFLUOROOLEFIN OXIDES
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The pyrolysis of perfluoroolefin oxides has been studied by gas chromatography/mass spectrometry at 400-700 deg C, in a current of He (1:10 dilution, contact time 1 sec).For oxides containing terminal CF2 group, the sole degradation route is through the elimination of difluorocarbene.Pyrolysis of symmetrical disubstituted oxides results in the elimination of a perfluoroalkylfluorocarbene, which subsequently isomerizes to the corresponding perfluoroolefin.In the pyrolysis of unsymmetric disubstituted oxides the elimination of perfluoroalkylfluorocarbenes occurs by both of the possible routes.Trisubstituted oxides eliminate bis-perfluoroalkylcarbenes.The decomposition of tetrasubstituted oxides proceeds along several directions concurrently.
- Kagramanov, N. D.,Kutin, A. A.,Peschanskii, N. V.,Zapevalov, A. Ya.,German, L. S.
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p. 1321 - 1325
(2007/10/02)
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