- PRODUCTION METHOD FOR FLUORO-ETHANE AND PRODUCTION METHOD FOR FLUORO-OLEFIN
-
The production method according to the present disclosure comprises obtaining a product containing the fluoroethane from a fluoroethylene by a reaction in the presence of catalysts. Each catalyst is formed by supporting a noble metal on a carrier. A reactor for performing the reaction is filled with a catalyst having a noble metal concentration of C1 mass % based on the entire catalyst and a catalyst having a noble metal concentration of C2 mass % based on the entire catalyst to form an upstream portion and a downstream portion, respectively; and C1C2. The reaction is performed by bringing the fluoroethylene represented by formula (3) and hydrogen gas into contact with the upstream portion and the downstream portion in this order.
- -
-
Paragraph 0087
(2021/10/15)
-
- Thermally conductive SiC as support of aluminum fluoride for the catalytic dehydrofluorination reaction
-
Aluminum fluoride (AlF3) is a typical catalyst for dehydrofluorination of hydrofluorocarbons (HFCs) to fluoroolefins with high heat of reaction. Consequently, heat supply and sintering are the key challenges for AlF3-based catalysts. Herein, SiC with high thermal conductivity and resistance to HF corrosion is suggested as a candidate support of AlF3 catalyst. The interaction between AlF3 and SiC leads to uniform distribution of the catalytic phase, and as a result of this, AlF3/SiC exhibits high catalytic activity and stability for the dehydrofluorination of 1,1-difluoroethane to vinyl fluoride. This study proposes a novel catalyst support (SiC) for strong endothermic catalytic reactions involving HFCs for the first time to the best of our knowledge.
- Han, Wenfeng,Li, Ying,Liu, Bing,Liu, Yongnan,Lu, Jiaqin,Tang, Haodong,Yang, Hong,Yu, Wei
-
-
- Rational design of MgF2 catalysts with long-term stability for the dehydrofluorination of 1,1-difluoroethane (HFC-152a)
-
In this study, three different approaches, i.e. the sol-gel method, precipitation method and hardlate method, were applied to synthesize MgF2 catalysts with improved stability towards the dehydrofluorination of hydrofluorocarbons (HFCs); the in situ XRD technique was employed to investigate the relationship between the calcination temperature and the crystallite size of precursors to determine optimal calcination temperature for the preparation of the MgF2 catalysts. Moreover, the physicochemical properties of MgF2 catalysts were examined via BET, XRD, EDS and TPD of NH3 and compared. Undoubtedly, the application of different methods had a significant influence on the surface properties and catalytic performances of MgF2 catalysts. The surface areas of the catalysts prepared by the precipitation method, sol-gel method and template method were 120, 215 and 304 m2 g-1, respectively, upon calcination at 200 °C. However, the surface area of the MgF2 catalysts decreased significantly when the calcination temperatures of 300 and 350 °C were applied. The catalytic performance of these catalysts was evaluated via the dehydrofluorination of 1,1-difluoroethane (HFC-152a). The MgF2 catalyst prepared by the precipitation method showed the lowest catalytic activity among all the MgF2 catalysts. When the calcination temperature was above 300 °C, the MgF2 catalysts prepared via the template method demonstrated the highest catalytic conversion rate with catalytic activity following the order: MgF2-T (template method) > MgF2-S (sol-gel method) > MgF2-P (precipitation method). The conversion rate generally agreed with the total amount of acid on the surface of the catalysts, which was measured by the NH3-TPD technique. The MgF2-T catalysts were further examined for the dehydrofluorination of HFC-152a for 600 hours, and a conversion rate greater than 45% was maintained, demonstrating superior long-term stability of these catalysts.
- Tang, Haodong,Dang, Mingming,Li, Yuzhen,Li, Lichun,Han, Wenfeng,Liu, Zongjian,Li, Ying,Li, Xiaonian
-
p. 23744 - 23751
(2019/08/13)
-
- Selective Copper Complex-Catalyzed Hydrodefluorination of Fluoroalkenes and Allyl Fluorides: A Tale of Two Mechanisms
-
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
-
supporting information
p. 11506 - 11521
(2019/08/20)
-
- Method for preparing vinyl fluoride by splitting 1,1-difluoroethane
-
The invention discloses a method for preparing vinyl fluoride by splitting 1,1-difluoroethane. The method comprises the following steps: in the presence of acetylene, under the effect of a catalyst, splitting 1,1-difluoroethan to obtain 1,1-difluoroethan. The method provided by the invention has the advantages of high raw material single-process conversion rate, low splitting reaction temperature, fewer impurities contained in vinyl fluoride, high selectivity and the like.
- -
-
Paragraph 0022; 0024-0025
(2017/07/20)
-
- A polyvinylidene fluoride preparation method and its catalyst preparation method
-
The invention discloses a preparation method of vinylidene fluoride and a preparation method of a catalyst used by the same. The preparation method of vinylidene fluoride comprises the following steps: mixing methane, oxygen and fluoroform or monochlorodifluoromethane or the mixed gas of fluoroform and monochlorodifluoromethane at any ratio or the mixed gas of multiple gases including fluoroform and monochlorodifluoromethane; adding O2 at a certain proportion, and reacting at a temperature of 550-1,050 DEG C under a total pressure of 1-10bar and at an air speed of 50-10,000h; and reacting in the presence of a catalyst to generate vinylidene fluoride. According to the method disclosed by the invention, the vinylidene fluoride with relatively high added value is generated under a catalytic action from several waste fluoroform raw materials which are cheap or need forced treatment, has relatively high added value, and brings good economic and social benefits.
- -
-
Paragraph 0031; 0032
(2017/08/25)
-
- METHOD FOR PRODUCING OLEFIN
-
A method for producing at least one olefin compound selected from the group consisting of a compound of formula (51), a compound of formula (52), a compound of formula (53), and a compound of formula (54), the method including reacting an olefin compound of formula (21) with a olefin compound of formula (31) in the presence of at least one metal catalyst selected from the group consisting of a compound of formula (11), a compound of formula (12), a compound of formula (13), a compound of formula (14), and a compound of formula (15).
- -
-
Paragraph 0150-0154; 0168-0171
(2017/11/01)
-
- Compositions
-
A composition comprising HCFO-1233xf and at least one additional compound selected from the group consisting of HCFO-1233zd, HCFO-1232xd, HCFO-1223xd, HCFC-253fb, HCFC-233ab, HFO-1234yf, HFO-1234ze, ethylene, HFC-23, CFC-13, HFC-143a, HFC-152a, HFO-1243zf, HFC-236fa, HCO-1130, HCO-1130a, HFO-1336, HCFC-244bb, HCFC-244db, HFC-245fa, HFC-245cb, HCFC-133a, HCFC-254fb, HCFC-1131, HCFO-1242zf, HCFO-1223xd, HCFC-233ab, HCFC-226ba, and HFC-227ca.
- -
-
Paragraph 0119; 0120
(2013/09/12)
-
- Titanium-catalyzed vinylic and allylic C-F bond activation-scope, limitations and mechanistic insight
-
The hydrodefluorination (HDF) of fluoroalkenes in the presence of a variety of titanium catalysts was studied with respect to scope, selectivity, and mechanism. Optimization revealed that the catalyst requires low steric bulk and high electron density; secondary silanes serve as the preferred hydride source. A broad range of substrates yield partially fluorinated alkenes, such as previously unknown (Z)-1,2-(difluorovinyl)ferrocene. Mechanistic studies indicate a titanium(III) hydride as the active species, which forms a titanium(III) fluoride by H/F exchange with the substrate. The HDF step can follow both an insertion/elimination and a σ-bond metathesis mechanism; the E/Z selectivity is controlled by the substrate. The catalysts' ineffieciency towards fluoroallenes was rationalized by studying their reactivity towards Group 6 hydride complexes. The broad application of the catalytic hydrofluorination of fluoroalkenes by the system [Cp2TiF 2]/silane is demonstrated. Isolated yields up to 79 % could be obtained for various substrates. Mechanistic studies indicate two competing reaction mechanisms. Copyright
- Kuehnel, Moritz F.,Holstein, Philipp,Kliche, Meike,Krueger, Juliane,Matthies, Stefan,Nitsch, Dominik,Schutt, Joseph,Sparenberg, Michael,Lentz, Dieter
-
supporting information
p. 10701 - 10714
(2013/01/14)
-
- Experimental and chemical kinetic study of the pyrolysis of trifluoroethane and the reaction of trifluoromethane with methane
-
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.
-
scheme or table
p. 751 - 760
(2010/09/04)
-
- Vapor phase hydrofluorination of acetylene to vinyl fluoride over La2O3-Al2O3 catalysts
-
A series of La-doped Al2O3 catalysts were prepared and tested for the vapor phase hydrofluorination of C2H2 to vinyl fluoride (CH2CHF, VF). It was found that the La-doped catalyst gave a stable cataly
- Bi, Qing-Yuan,Qian, Lin,Xing, Li-Qiong,Tao, Li-Ping,Zhou, Qiang,Lu, Ji-Qing,Luo, Meng-Fei
-
body text
p. 528 - 533
(2009/12/29)
-
- Shock tube study of dissociation and relaxation in 1,1-difluoroethane and vinyl fluoride
-
This paper reports measurements of the thermal dissociation of 1,1-difluoroethane in the shock tube. The experiments employ laser-schlieren measurements of rate for the dominant HF elimination using 10% 1,1-difluoroethane in Kr over 1500-2000 K and 43 2H3F in Kr, 415-1975 K, 5 2H4F2 in Kr, 700-1350 K, 6 down of 1600 cm-1, similar to that found in a previous examination of 1,1,1-trifluoroethane. Dissociation of vinyl fluoride is complicated by the presence of two parallel HF eliminations, both three-center and four-center. Structure calculations find nearly equal barriers for these, and TST calculations show almost identical k∞. An RRKM fit to the observed falloff again requires an unusually large 〈ΔE〉down and the experiments actually support a slightly reduced barrier. These large energy-transfer parameters now seem routine in these large fluorinated species. It is perhaps a surprising result for which there is as yet no explanation. the Owner Societies.
- Xu, Hui,Kiefer, John H.,Sivaramakrishnan, Raghu,Giri, Binod R.,Tranter, Robert S.
-
p. 4164 - 4176
(2008/09/19)
-
- PURIFICATION METHOD, PRODUCTION PROCESS, AND USE OF, 1, 1-DIFLUOROETHANE
-
Crude 1,1-difluoroethane containing at least one compound selected from the group consisting of unsaturated compounds each having two carbon atoms within the molecule and saturated chlorine-containing compounds each having two carbon atoms within the molecule is brought into contact with a zeolite and/or a carbonaceous adsorbent, or crude 1,1-difluoroethane containing hydrogen fluoride and, as impurities, at least one compound selected from the group consisting of unsaturated compounds each having two carbon atoms within the molecule is brought into contact with a fluorination catalyst in a gas phase state. High-purity 1,1-difluoroethane usable as a cryogenic refrigerant, or as an etching gas, can be produced in an industrially advantageous manner.
- -
-
Page/Page column 16-17
(2008/06/13)
-
- Efficient microscale preparation of isotopically enriched 1-[ 79Br]bromo-2-fluoroethylene, [79Br]BrHC=CHF
-
An efficient preparation of 1-[79Br]bromo-2-fliioroethylene, [79Br]BrHC= CHF, was carried out by a three-step procedure: (a) natural 1-bromo-2-fluoroethylene, BrHC=CHF, was iodinated to 1-fluoro-2-iodoethylene, FHC=CHI; (b) 1-fluoro-2-iodoethylene was 79Br2-brominated to 1,2-di[79Br]bromo-1-fluoro- 2-iodoethane, [79Br]BrFCHCH[79Br]BrI; and (c) 1,2-di[ 79Br]bromo-1-fluoro-2-iodoethane was dehalogenated to 1-[ 79Br]bromo-2-fluoroethylene, [79Br]BrHC=CHF. The yield of isolated product, on a 2-mmol scale, was 62% with respect to 79Br2. Copyright Taylor & Francis, Inc.
- Baldan, Alessandro,Tassan, Augusto
-
p. 1447 - 1453
(2007/10/03)
-
- CONVERSION OF FLUOROCARBONS
-
A process is disclosed for the conversion of fluorocarbons into fluorinated unsaturated compounds useful as monomers or other chemical precursors, such as C2H2F2. The process comprises reacting a hydrocarbon feed (20) and a fluorocarbon feed (10) in a high temperature reactor (26), at sufficiently high temperature and sufficiently short resident time to form a reaction product mixture (28) having the fluorinated unsaturated compound as the major reaction product, and cooling (18) to a temperature sufficiently low to inhibit polymerisation of the unsaturated compound. The reaction product may then be processed by removal of higher molecular weight compounds (35) and acids (32) and optionally separated (44) into product components.
- -
-
Page column 7-10
(2008/06/13)
-
- Gas-phase kinetics of the reactions of the CH2F radicals with the radicals CHF2, CH3, and C2H5
-
The mechanisms and the rates of the reactions of the fluorinated hydrocarbon radical CH2F with the fluorinated and pure hydrocarbon radicals CHF2, CH3, and C2H5, respectively, have been studied at low pressure (around 2 mbar) and room temperature using the discharge-flow reactor technique. Mass spectrometry either with electron impact or laser induced multiphoton ionization was applied for the detection of labile and stable species. The cross combination of the radicals is mainly followed by HF elimination from the chemically activated adduct. The overall rate coefficients at 298 K for CH2F + CHF2 → C2H2F2 + HF (1) CH2F + CH3 → C2H4 + HF (2) CH2F + C2H5 → C3H6 + HF (3) were derived from the analysis of the radical-time profiles by fit procedures; the following values were obtained: k1 = (3.0 + 1.5/ -0.7) × 1012 cm3 mol-1 s-1 k2 = (4.0 ± 1.5) × 1013 cm3 mol-1 s-1 k3 = (9.0 ± 3) × 1012 cm3 mol-1 s-1. The results are discussed in terms of chemical activation mechanisms.
- Beiderhase, Thomas,Hoyermann, Karlheinz,Nothdurft, Joerg,Olzmann, Matthias
-
p. 493 - 510
(2007/10/03)
-
- Thermal Decomposition of 2-Fluoroethanol: Single Pulse Shock Tube and ab Initio Studies
-
The thermal decomposition of 2-fluoroethanol (FEOH) was studied at 1000-1200 K behind reflected shock waves in a single pulse shock tube. The total pressures behind the reflected shocks varied between 13 and 23 atm. The products were CH3CHO, C2H3F, CH4, CO, C2H4, and C2H6. The unimolecular eliminations of HF and H2O were the major channels through which FEOH decomposed under these conditions. The rate constants for HF and H2O elimination were presented. The CH3CHO produced by HF elimination through the vinyl alcohol intermediate was chemically active and decomposed leading to CH4 and CH3CH3 products. Ethylene formation could be explained by considering C-O bond dissociation equally well. Direct real-time spectroscopic observation of HOF would be needed to choose between the two pathways. Ab initio (Hartree-Fock [HF] and second-order Moller-Plesset perturbation theory) and density functional theory [DFT] computations overestimated the barrier by 18 kcal/mole for HF elimination and 22 kcal/mole for H2O elimination, and including electron correlation improved the agreement. DFT predictions for activation energies for HF and H2O elimination reactions were within 1 kcal/mole of the experimental values.
- Rajakumar,Reddy,Arunan
-
p. 9782 - 9793
(2007/10/03)
-
- Treatment of chromium oxide and catalytic manufacture of vinyl fluoride
-
Advantageous processes are disclosed for the production of vinyl fluoride. Also disclosed are advantageous methods which may be employed for the preparation of catalysts useful in such processes. Included are methods which involve (i) reducing surface B2O3present in a bulk chromium oxide composition containing surface B2O3by treating said composition with HF at an elevated temperature and/or (ii) treating a bulk chromium oxide composition containing B2O3to enrich the B2O3present on its surface by heating said composition in oxygen or an oxygen-containing environment (e.g., air) at an elevated temperature for a time sufficient to enrich the B2O3on the surface of the composition by at least a factor of two compared to the surface analysis of the untreated bulk composition. Processes are provided herein which involve contacting 1,1-difluoroethane in the vapor phase with a trivalent chromium catalyst (preferably a trivalent chromium catalyst having primarily the morphology of alpha-chromium oxide and/or containing less than 1000 ppm alkali metal as the alkali metal oxide) wherein chromium is at least 95 atom percent of the metallic cations of said catalyst, at a temperature between about 225° C. and 375° C. Advantageous embodiments of these processes are disclosed wherein (i) the catalyst is prepared by reducing B2O3present in a bulk chromium oxide composition as indicated above, (ii) chromium is at least 99 atom percent of the metallic cations of the catalyst and/or (iii) the space velocity is from about 2000 volumes of 1,1-difluoroethane per volume of catalyst per hour.
- -
-
Page column 5-6
(2008/06/13)
-
- Gas-phase kinetics of the self reactions of the radicals CH2F and CHF2
-
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
-
p. 625 - 641
(2007/10/03)
-
- Absolute Rate Constant and Product Branching Fractions for the Reaction between F and C2H4 at T = 202-298 K
-
The discharge-flow kinetic technique coupled to mass-spectrometric detection has been used to determine the variable-temperature dependence of the rate constant and product branching fractions for the reaction between F(2P) and C2H4 at P = 1 Torr nominal pressure (He). The reaction was studied at T = 202 and 236 K by monitoring the decay of C2H4 in the presence of a large excess of F(2P). The overall rate coefficients were determined to be k1(202 K) = (1.7 ± 0.4) x 10-10 cm3 molecule-1 s-1 and k1(236 K) = (2.1 ± 0.5) x 10-10 cm3 molecule-1 s-1 with the quoted uncertainty representing total errors. Further, the branching fractions for the two observed reaction channels F + C2H4 → C2H3 + HF (1a) and F + C2H4 → C2H3F + H (1b) were determined by quantitatively measuring the yield of C2H3F under conditions of excess C2H4. The stabilized adduct, C2H4F, was not detected at T = 202 K. The derived branching fractions were Γ1a(202 K) = 0.25 ± 0.09, Γ1b (202 K) = 0.75 ± 0.16, and Γ1a(236 K) = 0.27 ± 0.13, and Γ1b (236 K) = 0.73 ± 0.20, where the quoted uncertainty represents total errors. By inclusion of k1(298 K) = (3.0 ± 0.8) x 10-10 cm3 molecule-1 s-1, a revised value that used data from our previous study and Γ1a(298 K) = 0.35 ± 0.04 and Γ1b (298 K) = 0.65 ± 0.04 from a laser photolysis/photoionization mass spectrometry study, we obtain the Arrhenius expressions k1a(T) = (7.5 ± 4.0) x 10-10 exp[(-1.2 ± 0.3)/(RT)] and k1b(T) = (5.2 ± 1.0) x 10-10 exp[(-0.6 ± 0.1)/(RT)] in units of cm3 molecule-1 s-1 for k and in units of kcal mol-1 for activation energy. The quoted uncertainty represents total errors at 1σ precision errors plus 15% systematic errors. RRKM calculations have shown that the critical energy for H addition to C2H3F is less than 6 kcal mol-1 larger than that for the addition of F to C2H4 and that the competitive decomposition of chemically activated C2H4F radicals favor C-H bond rupture by a factor greater than 1000 over that for C-F bond rupture.
- Nesbitt, Fred L.,Thorn Jr., R. Peyton,Payne Jr., Walter A.,Tardy
-
p. 4470 - 4479
(2007/10/03)
-
- Formation of β-Fluoroethyl Radical and Closed-Shell Products in Reactions of Photogenerated Fluorine Atoms with Ethene in Solid Argon
-
Solid-state reactions of F atoms with ethene molecules were initiated by UV photolysis of dilute solutions of F2 and C2H4 in solid Ar.Products stabilized in the matrix were detected by infrared spectroscopy.Experiments were conducted at different temperatures in order to distinguish reactions in matrix-isolated F2-C2H4 complexes (at 16 K) from reactions of diffusing thermal F atoms (at 26 K).Comparison with the kinetic EPR data (Benderskii, V.A. et al.Mendeleev Commun. 1995, 6, 245) permitted the identification of the infrared spectrum of the β-fluoroethyl radical, which is the main product of the F + C2H4 reaction.Frequencies and absolute absorption intensities of the eight strongest infrared bands of β-C2H4F are reported.Photolysis of isolated F2-C2H4 complexes forms the closed-shell products C2H3F-HF and trans- and gauche-1,2-C2H4F2 with relative yields 0.6:0.2:0.2.Successive addition of two thermal F atoms to an isolated C2H4 molecule forms only the two conformers of 1,2-C2H4F2.The difference between product branching ratios of the latter reaction and the direct photoinduced reaction of F2-C2H4 complexes is qualitatively explained by the difference in size of the reaction cages and excess energies of the vibrationally excited intermediate (C2H4F2)*.
- Misochko, Eugenii Ya.,Benderskii, Alexander V.,Wight, Charles A.
-
p. 4496 - 4502
(2007/10/03)
-
- Ion-Molecule Reactions of CF3+ with Simple Unsaturated Aliphatic Hydrocarbons at Near-Thermal Energy
-
Ion-molecule reactions of CF3+ with C2H2, C2H4, and C3H6 have been studied at near-thermal energy (0.05 eV) by using an ion beam apparatus.Initial product ion distributions and reaction rate constants were determined and compared with previous beam and selected ion flow tube (SIFT) data.The CF3+/C2H2 reaction produces exclusively the electrophilic adduct C3H2F3+ ion.For C2H4 and C3H6, hydride abstraction and electrophilic addition followed by HF elimination or fluoride transfer occur in parallel.The branching ratios of the former and latter reactions are 0.29 +/- 0.04:0.71 +/- 0.06 for the CF3+/C2H4 reaction and 0.07 +/- 0.02:0.93 +/- 0.07 for the CF3+/C3H6 reaction.On the basis of theoretical calculations of potential energies for the CF3+/C2H2 and CF3+/C2H4 systems, the lack of the HF elmination channel in the CF3+/C2H2 reaction, whereas the lack of the initial adduct ion in the CF3+/C2H4 reaction, is attributed to the different stability of the intermediate adduct ions for HF elimination.The reaction rate constants were 0.45 x 1E-9, 1.3 x 1E-9, and 1.6 x 1E-9 cm3 s-1 for C2H2, C2H4, and C3H6, respectively, which correspond to 46percent, 120percent, and 130percent of calculated rate constants from Langevin theory or a parametrized trajectory model.Although there are significant discrepancies in the product ion distributions between the present beam experiment and the previous beam data, the product ion distributions and the reaction rate constants obtained here are in reasonable agreement with the previous SIFT data.
- Tsuji, Masaharu,Aizawa, Masato,Nishimura, Yukio
-
p. 3195 - 3200
(2007/10/02)
-
- Elementary Reactions in the C-H-F-System
-
The elementary reactions in the C-H-F-system F + CH3F --> CH2F + HF (1); F + CH2F --> CHF2 + H (2a); --> CHF + HF (2b) and CH2F + CH2F --> products (3), as well as CH3 + F --> CH2F + H (4a); --> CH2 + HF (4b) were studied in an isothermal flow reactor at room temperature and a nozzle reactor (T = 220 K) with mass spectrometric and laser induced detection devices.The rate constants k1 (T) = 2.1E13 (T/300 K)2.4 cm3/mol*s, k2a (300 K) = 5E13 cm3/mol*s, k2b (300 K) = 5E13 cm3/mol*s, k3 (300 K) = 7.5E12 cm3/mol*s, and k4 (300 K) = 6.8E13 cm3/mol*s were determined.The products of the reaction (3) were found to be C2H4F2 and C2H3F + HF.The pathway leading to C2H3F + HF was detected as the main product channel (>50percent).The rate and product distribution of reaction (3) was determined to be independent of pressure in the range 1 /= p (He)/mbar /= 7 and with quenching gases He, CO2 and SF6.In the reaction (4) the pathway (4a) contributes 12percent, and the H atom abstraction (4b) is with 88percent the main pathway. - Key words: Elementary reactions / Reaction kinetics / Mass spectrometry / Radical reactions (CH2F, CH3) / Atom reactions (F)
- Beiderhase, Th.,Hack, W.,Hoyermann, K.
-
p. 227 - 242
(2007/10/02)
-
- Perfluorination of Allene Derivatives by Direct Fluorination
-
Perfluoropropane was prepared from allene with elemental fluorine in the presence of sodium fluoride in 84percent yield for the first time.The reaction of allene with elemental fluorine afforded 2,2-difluoropropane in the absence of sodium fluoride.Methoxyallene and cyanoallene were perfluorinated with elemental fluorine in the presence of sodium fluoride to give heptafluoropropyl trifluoromethyl ether and heptafluoropropyl cyanide in good yields respectively.In addition, the direct fluorination of cyanoallene in the presence of cesium fluoride afforded N,N-difluorononafluorobutylamine in 95percent yield.
- Arimura, Takashi,Shibakami, Motonari,Tamura, Masanori,Kurosawa, Shigeru,Sekiya, Akira
-
p. 588 - 598
(2007/10/02)
-
- Displacement Reaction Dynamics of Fluorine Atoms with Vinyl Bromide Molecules
-
Reactive scattering of F atoms with C2H3Br molecules leading to both H and Br atom displacement has been studied at an initial translational energy E ca. 40 kJ mol-1 using a supersonic beam of F atoms seeded in He buffer gas.The center-of-mass angular distribution of C2H3F reactive scattering shows a sharp forward peak with a lower backward peak of relative intensity ca. 0.5.The product translational energy distribution peaks at a low fraction f'pk ca. 0.1 of the total available energy with a tail extending up to higher energy.The branching ratio ca. 10 strongly favors Br atom displacement.The H atom displacement pathway occurs in competition with F atom migration in the FCH2CHBr. radical formed by F atom addition to the C=C double bond.The Br atom displacement occurs in the .CH2CHBrF radical formed either by F atom migration from FCH2CHBr. or directly from F atom addition to the C=C double bond.In either case, Br atom displacement occurs rapidly compared with the rate of F atom migration over the potential energy barrier in the bridged configuration, resulting overall in a short-lived collision complex mechanism for the formation of C2H3F reaction products.
- Zhu, Z. Z.,Smith, D. J.,Grice, R.
-
p. 4003 - 4007
(2007/10/02)
-
- INVESTIGATIONS IN THE REGION OF INDUSTRIAL FLUORINATED COMPOUNDS
-
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.
-
p. 1935 - 1940
(2007/10/03)
-
- Two-color multiphoton decomposition of 1-bromo 2-fluoroethane
-
Multiphoton decomposition of 1-bromo 2-fluoroethane (CH2BrCH2F, BFE) with a two-color CO2 infrared laser is reported as a function of number of laser pulses. For single color irradiation at a wavelength chosen to excite BFE, the decomposition product, vinyl fluoride, which accumulates during the many-pulse MPD experiment, is found to deactivate BFE decomposition. When a second laser, tuned to a vinyl flouride absorption is introduced, coincident with the first, the vinyl fluoride is found to activate further BFE decomposition. These results are accounted for in terms of a pressure-dependent model. Changes in model parameters, upon addition of the second laser, are shown to be consistent with interpretations in terms of collision-dependent reaction schemes.
- Mcrae,Ivanco,Goodale
-
p. 147 - 158
(2007/10/03)
-
- HIGH-ENERGY TRANSFORMATIONS OF POLYFLUOROALKANES. IX. PYROLYSIS OF 1,1-DIFLUOROETHANE
-
Kinetics of the unimolecular thermal dehydrofluorination of 1,1-difluoroethane in a flow reactor is reported. The first-order rate constant is determined: logk = (-60,000+/-2000)/4.569*T+13.33+/-0.10. 1,1-Difluoroethylene, as a by-product of the pyrolysis of 1,1-difluoroethane, is formed by a radical mechanism, for which a heterogeneous initiation stage is proposed. MNDO calculations show the predominant formation of the CH3-C.F2 radical at the initiation stage. For this radical, rate constants of unimolecular 1->2 and 2->1 hydrogen shifts are determined within the framework of the PPKM statistical theory.
- Mitin, P. V.,Golovin, A. V.,Grigor'eva, T. Yu.,Barabanov, V. G.
-
-
- Infrared Laser-induced Chemistry of Chlorodifluoromethane-Silane Mixtures at Two Irradiating Wavelengths
-
Chemical reactions induced by single- and two-wavelenght CO2 laser radiation in a mixture of silane and chlorodifluoromethane are initiated by the reaction between: CF2 and SiH4 and afford volatile carbonaceous products with C-H bonds, together with a solid deposit consisting of silicon carbide and highly reactive Si/C/H/F polymeric material.The results are in line with the reduction of the strong C-F bond of difluorocarbene and with the production of H2Si=CF2 silene as intermediate which undergoes dehydrofluorination and polymerization.
- Diaz, L.,Santos, M.,Sigueenza, C. L.,Simeonov, S. A.,Gonzalez-Diaz, P. F.,et al.
-
p. 3907 - 3912
(2007/10/02)
-
- IR Laser-induced Chemistry of some Perhaloethene-Silane Mixtures at Different Single Irradiating Wavelengths
-
TEA CO2 laser-induced reactions in chlorotrifluoroethene-silane, 1,2-dichlorodifluoroethene-silane, 1,1-dichlorodifluoroethene-silane, and 1,2-dichlorodifluoroethene-trimethylsilane mixtures at medium (4-19 Torr) and in chlorotrifluoroethene-silane and 1,2-dichlorodifluoroethene-silane mixtures at low (1 Torr) pressures can be initiated by irradiation tuned to either perhaloethene or silane.The reaction progress at medium pressure and reaction products at low pressure depend on the particular wavelength employed.The former reactions are assumed to occur through reactive collision of both energized components in the mixture and have been shown to yield mostly tetrafluorosilane, trifluorosilane, hydrogen chloride, and other hydrocarbons.The latter are explained by multiphoton dissociation of the alkene into carbenes, subsequent reactions of these carbenes, and by 1,2-rearrangement of halogen in the transient CFCl=CF* radical produced upon C-Cl bond cleavage of the parent CFCl=CFCl compound.This reaction mechanism is in line with IR multiphoton decomposition of 1,2-dichlorodifluoroethene both in the absence and presence of chlorine and carbon monoxide.
- Pola, Josel,Simeonov, Sawa
-
p. 101 - 108
(2007/10/02)
-
- Dehydrofluorination and dehydrogenation of fluorinated alkanes
-
Fluorinated alkanes are converted into correspond-ing unsaturated dehydrofluorination products by contact with a catalyst bed containing γ-fluorided alumina in the presence of a co-reactant gas at a reaction temperature of from about 200°C to about 700°C, the catalyst bed having been prepared by the steps of (a) flowing air over a catalyst bed containing γ-alumina for a contact time of from about 5 seconds to about 150 seconds, at a temperature of from about 600°C to about 750°C, and (b) thereafter flowing hydrogen fluoride over the air-treated catalyst bed at elevated temperature to convert the γ-alumina to γ--fluorided alumina. The co-reactant gas contains oxygen, carbon dioxide or mixtures thereof. The γ-fluorided alumina-containing catalyst may also be utilized to convert 1,1-difluoroethane to its dehydrogenation product, vinylidene fluoride at a reaction temperature of from about 300°C to about 700°C.
- -
-
-
- The translational energy dependence of the F + C2H4 -> H + C2H3F reaction cross section near threshold
-
We have carried out crossed molecular beam studies of the substitution reaction F + C2H4 -> H + C2H3F in the collision energy range 0.8-2.5 kcal/mol using a velocity selected F atom beam.The relative substitution cross section is found to decrease with increasing collision energy indicating that if there is a potential energy barrier to F atom addition to C2H4 it is much less than 0.8 kcal/mol and that the transition state for addition occurs early along the reaction coordinate.These results agree well with ab initio calculations.Although the product translational energy distributions are similar to those obtained from earlier work at higher collision energies, the C2H3F angular distributions suggest that a wider range of rectant approach geometries lead to products at lower energies.
- Robinson, Gary N.,Continetti, Robert E.,Lee, Yuan T.
-
p. 275 - 284
(2007/10/02)
-
- The effect of collisions in the multiphoton decomposition of 1-bromo-2-fluoroethane
-
The multiphoton decomposition (MPD) of 1-bromo 2-fluoroethane, CH2BrCH2F, with a pulsed CO2 infrared laser is reported.The decompsition study was done at constant fluence and at pressures up to 2 kPa.Empirical representations of the pressure dependence of the MPD are reported.A collision-dependent reaction scheme is presented to explain the pressure dependence of the up-pumping through the vibrational manifold.
- McRae, Glenn A.,Evans, D. K.,Goodale, J. W.
-
p. 1689 - 1694
(2007/10/02)
-
- Computational Studies of the Bimolecular Reaction Dynamics of the C2H4 + F2 System
-
The bimolecular reaction dynamics of C2H4 + F2 on a previously described potential energy surface have been investigated by using quasi-classical trajectory methods.All important reaction channels are open on this potential surface, and the calculated equilibrium geometries, reaction exothermicities and fundamental vibration frequencies are in fair-to-good accord with measured values.The major reaction products are found to be either CH2CH2F + F or CH2=CHF + HF. 1,2-Difluoroethane is found as a reaction intermediate leading to CH2=CHF + HF but is never observed as a final product.The calculated reaction cross sections are all less than 5 Angstroem2 even for translational energies more than 1 eV in excess of the reaction threshold.Almost all of the reaction exothermicity is partitioned into the internal modes of CH2CH2F or CH2=CHF.Very little of this energy appears as relative translational motion of the products.HF is usually formed in the ν = 0, 1, or 2 vibrational state.The calculated center-of-mass differential cross section for fluorine atom scattering shows a strong backward component along with an isotropic component.The first of these is shown to arise from a direct reaction mechanism; the second is the result of complex formation.Formation of fluoroethylene is shown to occur via a complex mechanism involving formation of 1,2-difluoroethane as an intermediate.The calculated thermal rate coefficients for CH2CH2F and CH2=CHF formation are 1.38E14*exp and 1.90E13*exp cm3/(mol*s), respectively.There is some suggestion of mode-specific rate enhancement for the reaction leading to CH2CH2F but not for the formation of CH2=CHF.In the first case, the C-H stretching modes are found to be the most effective in enhancing the rate.The results are compared and contrasted with gas-phase data reported by Kapralova et al. and with the matrix isolation results obtained by Frei et al.
- Raff, Lionel M.
-
p. 141 - 147
(2007/10/02)
-
- Quenching of CHF 1A'' (0,02 after Single Vibronic Level Excitation by the Diatomic Molecules H2, O2 and CO
-
The elementary deactivation processes of CHF(, v'2) by H2(X1Σg+), O2(X3Σg-, and CO(X1Σ+) were studied in a quasistatic photolysis chamber.Determination of time and spectrally resolved laser-induced fluorescence of CHF (1A'', v'2) in single vibronic excited levels (SVL) (0 2 1A' (0,0,0)> was generated in the fluorescence cell by multiphoton dissociation (MPD) of CH2F2.The overall CHF(, v'2)-depletion rate constants: .Asignificant increase of the rate constants for higher vibronic states was observed.The contribution of vibration deactivation to the overall depletion of the initially excited state was found to be small (2 = 1 and Δv'2 = 2 respectively.The reaction mechanisms are discussed. - Keywords: Elementary Reactions / Energy Transfer / Photochemistry
- Dornhoefer, G.,Hack, W.
-
p. 485 - 490
(2007/10/02)
-
- Application of multi-photon ionization mass spectrometry to the study of the reactions O + C2H4, F + C3H6, F + c-C3H6, F + CH3OH, H + CH2OH and O + CH3O
-
The experimental arrangement of a time-of-flight mass spectrometer with multi-photon ionization and electron impact ionization is described. This set up was combined with a discharge flow reactor and a molecular beam sampling device. The detection of the radicals CH3, C3H5, CH2OH and their deuterated analogs by the wave-length selective multi-photon ionization allowed the identification of primary products of elementary reactions in the gas-phase (around 1 mbar).
- Heinemann-Fiedler,Hoyermann
-
p. 1472 - 1477
(2007/10/02)
-
- Laser-Induced Reactions of Hexafluorobenzene and Selected Hydride Compounds
-
Infrared-laser-induced reactions between C6F6 and general hydrides R-H (R = H, D, CH3, HCC, H2C=CH, and Cl) were studied by irradiating C6F6 at 1027 cm-1 in C6F6/R-H mixtures.In general, two competitive pathways involving C-F bond cleavage in C6F6 were observed as follows: (1) C6F6 + R-H C6F5H + R-F and (2) C6F6 + R-H C6F5R + HF.C6F6 decomposition also took place to a minor extent depending on the mole fraction of C6F6 and gave rise to C2F4 and C2H2.From infrared and GC/MS analysis of the product mixtures after 20-200 pulses, C6F5H was observed in all reactions except that involving D2.When D2 was used C6F5D was the major product.C6F5H was the major product in the reactions involving H2 and C2H2.In the reaction with C2H4, C6F5H was the major product derived from C6F6 though C2H2 was the major product of the reaction.The large amount of C2H2 seems to be derived from an additional sensitized decomposition of C2H4.C6F5H was present in minor amounts in the reaction with CH4 and HCl.Besides C6F5H, other monosubstituted products derived from C6F6 were also formed, generally within 20-100 pulses.Thus, C6F5CH3, C6F5CH=CH2, C6F5CCH, and C6F5Cl were produced, respectively, in the reaction of C6F6 with CH4, C2H4, C2H2, and HCl.In the first and last cases these products were the major ones observed.The results are discussed mechanistically in terms of the initial formation of the C6F5. radical and synthetically in terms of the utility of obtaining selective-laser-induced reduction of C6F6.
- Koga, Yoshinori,Chen, Ruth,Keehn, Philip M.
-
p. 306 - 311
(2007/10/02)
-
- CATALYTIC SYNTHESIS OF VINYL FLUORIDE FROM 1,1-DIFLUOROETHANE AND ACETYLENE.
-
Gas-phase catalytic dehydrofluorination of 1,1-difluoroethane (DFE) is one of the main methods for the production of vinyl fluoride (VF), the starting monomer for the production of polyvinyl fluoride (PVF) and various fluorine-containing copolymers. However, in this method hydrogen fluoride (HF) is evolved as a by-product, recovery of which is a very labor-consuming and costly process. In order to avoid this drawback and to raise the VF yield, we studied simultaneous dehydrofluorination of DFE and hydrofluorination of acetylene (Ac). The joint reactions of DFE dehydrofluorination and Ac hydrofluorination under various conditions in the presence of two-component aluminum-iron and three-component aluminum-iron catalysis showed that these catalysts have satisfactory activity and selectivity. The most effective of the catalysts studied was a three-component catalyst of the composition (mole %): 88 gamma -Al//2O//3 plus 8Fe//2O//3 plus 4CdO.
- Sirlibaev,Akramkhodzhaev,Usmanov
-
p. 1541 - 1543
(2007/10/02)
-
- Process for the preparation of fluorinated nitroalkanes
-
In the conjugated nitrofluorination of an olefin by reacting an olefin of the formula STR1 in which R1, R2, R3 and R4 each independently is hydrogen, fluorine, chlorine, bromine, alkyl, halogenoalkyl or cycloalkyl, or R2 and R4 together are an alkylene radical of 3 to 6 carbon atoms, with hydrogen fluoride and nitric acid to produce an α-fluorinated nitroalkane of the formula STR2 the improvement which comprises effecting the reaction in a vessel protected against corrosion employing about 1 to 1.1 mols of hydrogen fluoride and about 1 to 2 mols of nitric acid per mol of olefin. The process uses much less HF than heretofore and the products are useful intermediates in making herbicides. Some of the products are new.
- -
-
-
- Infrared Multiphoton Decomposition of 1-Chloro-1-fluoroethene
-
Unimolecular dissociation and subsequent reactions of CH2=CFCl subjected to the infrared multiphoton excitation were studied with a focused geometry using the P(10) line of the 10.6 μm CO2 band at 952.9 cm-1.The final products of the photolysis observed were CH=CCl, CH=CF, CH=CH, CH2CHF, and CH2=CF2.A series of diagnostic experiments shows that the primary processes of photolysis involve the molecular elimation of HF and HCl, to minor extend C-Cl bond rupture.The relative importance of the primary steps is tentatively estimated to be approximately 100:65:25, respectively.Primarily formed CH=CCl and CH=CF suffer from secondary photolysis absorbing additional photons.More fraction of CH=CF primary yield is decomposed than that of CH=CCl, due to the accidental resonance with the laser excitation line.CH=CH and CH2=CHF are concluded to be formed by the H atom abstraction reaction of CH2=C. and CH=CF. radicals generated during the photolysis respectively, CH2=CF2 beging formed by the recombination reaction between CH2=CF. radical and F atom.In the shock tube pyrolysis the formation of CH=CF predominates over that of CH=CCl.A mechanistic change to form CH=CF in the shock tube pyrolysis is suggested.
- Ogura, Hiroo
-
p. 1358 - 1366
(2007/10/02)
-
- A Photoelectron Spectroscopic Study of the Ground States of CH2F+ and CD2F+
-
The fluorine atom/methyl fluoride reaction has been studied by photoelectron spectroscopy.A new product band with vibrational components at 9.04 +/- 0.01 eV adiabatic and 9.22 +/- 0.01 eV vertical ionization energies is assigned to the CH2F free radical.The ν'= 0-1 vibronic separation measured as 1450 +/- 30 cm-1 is due to the C-F stretching fundamental of the ground state of CH2F+; this vibronic interval was 1530 +/- 30 cm-1 for CD2F+.The positive deuterium shift for CH2F+ is due to interaction with the H-C-H bending mode, which shifts below the C-F stretching mode on deuteration.The substantial increase in the C-F stretching modes for CH2F+ and CD2F+, as compared to 1163- and 1193-cm-1 values for the CH2F and CD2F free radicals in solid argon, respectively, is due to increased net C-F bonding in the cations.
- Andrews, Lester,Dyke, John M.,Jonathan, Neville,Keddar, Noureddine,Morris, Alan,Ridha, Abed
-
p. 2364 - 2368
(2007/10/02)
-
- A Reinvestigation of the First Band in the Photoelectron spectrum of the Ethyl Radical
-
The first photoelectron band of the ethyl radical, produced from the reaction of fluorine atoms with ethane, has been recorded with a new multidetector photoelectron spectrometer using He I radiation.A regular vibrational series (with average separations of 400 +/- 30 cm-1) was observed which is attributed to excitation of the pyramidal bending mode in the ion.The vertical ionization energy of the observed band is measured as 8.51 +/- 0.01 eV and an upper limit of the adiabatic ionization energy is obtained as 8.26 +/- 0.02 eV.Two other methods of generating the ethyl radical, namely, pyrolysis of azoethane and pyrolysis of n-propyl nitrite, are shown to be less suitable sources for PES investigatios of this radical.
- Dyke, J. M.,Ellis, A. R.,Keddar, N.,Morris, A.
-
p. 2565 - 2569
(2007/10/02)
-
- Vacuum Ultraviolet Photochemistry of Fluoroethene and 1,1-Difluoroethene
-
Products from the broad-band vacuum ultraviolet photolysis of CH2CHF and CH2CF2 were collected by using a novel gas collection technique and analyzed by using gas chromatography.The primary route of decay for both parents is through α-β elimination of HF.Primary branching ratios for HF elimination, F atom ejection, and HH elimination from CH2CHF were determined: 0.82, 0.13, and 0.05, respectively.The technique does not permit detection of single H atom ejection.The ratio of (C2F2H3) stabilization by He vs. decomposition, formed by the addition of F to CH2CHF, is 0.029 +/- 0.004 torr-1.The lifetime of the excited complex is approximately a factor of 5 longer relative to other related systems.A less detailed study of excited-CH2CF2 decay indicates similar trends.
- Sirkin, Eric R.,Pimentel, George C.
-
p. 1833 - 1840
(2007/10/02)
-
- Extent of the Displacement Route in the Reactions of Fluorine Atoms with Ethylene. Vinyl Chloride, and Vinyl Bromide
-
The chemical branching of three fluorine-atom reactions, those with C2H4, C2H3Cl, and C2H3Br, was studied in real-time experiments using a tubular reactor coupled to a photoionization mass spectrometer.The fluorine atoms were generated by the CO2-laser-induced secondary photolysis of C6F5Cl which also appears to produce tetrafluorobenzene (c-C6F4).The measured fractional extents that the three reactions studied proceed by a displacement route at 295 K (to yield C2H3F + X) are 0.65 (+/-0.06), 0.72 (+/-0.14), and 0.72(+/-0.14) for C2H4, C2H3Cl, and C2H3Br, respectively.
- Slagle, Irene R.,Gutman, David
-
p. 1818 - 1821
(2007/10/02)
-
- Reactions of Fluoromethyl Radicals
-
1,3-difluoroacetone was photolysed by itself and in the presence of either diethylketone or di-isopropylketone and the rates of the following reactions of fluoromethyl radicals were measured: (i) CH2F + CH2FCOCH2F, log10 (k/cm3 mol-1 s-1) = 11.10 -40000/2.303RT, (ii) CH2F + C2H5COC2H5, log10 (k/cm3 mol-1 s-1) = 10.71 -34050/2.303RT, (iii) CH2F + i-C3H7CO-i-C3H7, log10 (k/cm3 mol-1 s-1) = 11.18 -31550/2.303RT where R= 8.314 J mol-1 K-1.The disproportionation-combination ratios (Δ) for the following pairs of radicals were found to be Δ(CH2F, C2H5) = 0.047, Δ(CH2F, i-C3H7) = 0.210, Δ(i-C3H7, i-C3H7) = 0.55, Δ(C2H5, C2H5) = 0.146.
- Cadman, Philip,Owen, Howell L.
-
p. 3087 - 3106
(2007/10/02)
-
- Vibrational Energy Transfer Probabilities of Highly Vibrationally Excited Fluoroethane and 1,2-Difluoroethane Molecules
-
The collisional loss of vibrational energy from chemically activated CH3CH2F and CH2FCH2F formed with average energies of 91 and 92.5 kcal mol-1, respectively, has been studied at 300 K with four bath gases, SF6, CO2, N2, and He.These chemically activated molecules were formed by combination of CH3 with CH2F and of CH2F with CH2F.The data cover an extensive range of pressure and permit the assignment of the mean energy transfer per collision and the form of the transition probability distribution.For He the (ΔEd) values were 1.0 kcal mol-1 with an exponential distribution for both C2H5F and C2H4F2.The (ΔEd) values for C2H5F or C2H4F2 were virtually the same and ranged from 2.0 to 5.0 kcal mol-1 for N2, CO2, and SF6; these transition probability distributions were of the Gaussian type (represented here by a stepladder model).The results for CH3CH2F and CH2FCH2F are compared to previous findings for CH3CF3 and CH2ClCH2Cl from this laboratory.The deactivation efficiency for SF6 is similar for all four molecules.However, the deactivation of CH3CF3 by N2 and CO2 is less efficient than for the other three molecules.The He deactivation efficiencies for the fluoroethanes are all similar, but substantially smaller than for C2H4Cl2.
- Richmond, G.,Setser, D. W.
-
p. 2699 - 2705
(2007/10/02)
-
- Effects of Polar β Substituents in the Gas-Phase Pyrolysis of Ethyl Acetate Esters
-
The rates of the gas phase pyrolysis of six β-substituted ethyl acetates were studied in a static system over the temperature range 319-450 deg C and the pressure range 63-207 mmHg.In seasoned vessels the reactions are homogenous, follow a first-order rate law, and are unimolecular.The temperature dependence of the rate constants is given by the following Arrhenius equations for the compounds indicated: 2-(dimethylamino)ethyl acetate, log k(s-1) = (13.90 +/- 0.30) - (220.4 +/- 3.8) kJ*mol-1 (2.303RT)-1; 2-methoxyethyl acetate, log k(s-1) = (12.04 +/- 0.24) -(203.7 +/- 2.9) kJ*mol1- (2.303RT)-1; 2-(methylthio)ethyl acetae, log k(s-1 = (11.27 +/- 0.39) - (179.0 +/- 4.6) kJ*mol-1 (2.303RT)-1; 2-chloroethyl acetate, log k(s-1) = (12.14 +/- 0.66) - (202.0 +/- 8.4)kJ*mol-1 (2.303RT)-1; 2-fluoroethyl acetate, log k(s-1) = (12.68 +/- 0.60) - (211.2 +/- 7.1) kJ*mol-1 (2.303RT)-1; 2-cyanoethylacetate, Log k(s-1) = (11.51 +/- 0.13) - (171.9 +/- 1.7) kJ*mol-1 (2.303RT)-1.The effect of substituents in the gas-phase elimination of β-substituted ethyl acetates may be grouped in three types.The linear correlation of several -I electron-withdrawing groups along strong ? bonds is presented and discussed.A small amount of anchimeric assistance is proposed in the pyrolysis of the 2-(methyltio)ethyl acetate.The experimental data are consistent with the transition state where the Cα-O bond polarization is the rate-determining process.
- Chuchani, Gabriel,Martin, Ignacio,Hernandez, Jose A. A.,Rotinov, Alexandra,Fraile, German,Bigley, David B.
-
p. 944 - 948
(2007/10/02)
-
- Preparation and some reactions of difluoroborane
-
Difluoroborane is produced by the direct interaction of boron trifluoride with diborane in the gas phase at 100° or above. Pyrolysis of BF3-B2H6 mixtures at 250° for periods of 30 min to 1 hr, followed by rapid quenching,
- Coyle,Cooper,Ritter
-
p. 1014 - 1020
(2008/10/08)
-