- Formation of CF3O- in the gas phase
-
We report experimental studies of the formation of CF3O- by ion-molecule and electron attachment reactions, and theoretical investigations of the structure and energetics of CF3O- and its neutral counterpart CF3O. The anion CF3O- is formed from the rapid attachment of free electrons to its neutral dimer, (CF3O)2. Potential sources of CF3O- through ion-molecule reactions of CF3- and F- were surveyed. CF3O- is formed in the bimolecular ion-molecule reaction of CF3- with SO2 and the third-order association reaction of F- with CF2O. In addition, rate constants for the reactions of CF3- with a variety of neutral compounds were measured. A number of cases were found in which formation of CF3O- was energetically allowed but was not observed. The potential energy surfaces of CF3O and CF3O- have been investigated using a variety of density functional theory (DFT) techniques. The ground-state minimum energy structure of CF3O was found to be a 2A′ Jahn-Teller distorted Cs-symmetry structure, while for the anion the ground state is 1A1 with a C3v-symmetry minimum. A search for other low-energy minima for CF3O- was unsuccessful. The DFT methods support a value for the adiabatic electron affinity of CF3O near 4.1 eV.
- Morris, Robert A.
-
-
Read Online
- Direct Superacid-Promoted Difluoroethylation of Aromatics
-
Under superacid conditions, aromatic amines are directly and regioselectively 1,1-difluoroethylated. Low temperature in situ NMR studies confirmed the presence of benzylic α-fluoronium and α-chloronium ions as key intermediates in the reaction. This method has a wide substrate scope and can be applied to the late-stage functionalization of natural alkaloids and active pharmaceutical ingredients.
- Artault, Maxime,Martin-Mingot, Agnès,Thibaudeau, Sébastien,Vitse, Kassandra
-
supporting information
(2021/12/22)
-
- Using Chlorotrifluoroethane for Trifluoroethylation of (Hetero)aryl Bromides and Chlorides via Nickel Catalysis
-
A nickel-catalyzed reductive cross-coupling between industrial chemical CF3CH2Cl and (hetero)aryl bromides and chlorides has been reported. The reaction is synthetically simple without the preparation of arylmetals and exhibits high functional group tolerance. The utility of this protocol has been demonstrated by the late-stage modification of pharmaceuticals, providing a facile route for medicinal chemistry.
- Li, Xuefei,Gao, Xing,He, Chun-Yang,Zhang, Xingang
-
supporting information
p. 1400 - 1405
(2021/02/20)
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- C(sp3)-CF3Reductive Elimination from a Five-Coordinate Neutral Copper(III) Complex
-
The reductive elimination from a high-valent late-transition-metal complex for the formation of a carbon-carbon or carbon-heteroatom bond represents a fundamental product-forming step in a number of catalytic processes. While reductive eliminations from well-defined Pt(IV), Pd(IV), Ni(III)/Ni(IV), and Au(III) complexes have been studied, the analogous reactions from neutral Cu(III) complexes remain largely unexplored. Herein, we report the isolation of a stable, five-coordinate, neutral square pyramidal Cu(III) complex that gives CH3-CF3 in quantitative yield via reductive elimination. Mechanistic studies suggest that the reaction occurs through a synchronous bond-breaking/bond-forming process via a three-membered ring transition state.
- Liu, Shuanshuan,Liu, Shuanshuan,Liu, He,Liu, Shihan,Lu, Zehai,Lu, Changhui,Leng, Xuebing,Lan, Yu,Shen, Qilong
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supporting information
p. 9785 - 9791
(2020/07/10)
-
- Improved Access to Organo-Soluble Di- and Tetrafluoridochlorate(I)/(III) Salts
-
A facile one-pot gram-scale synthesis of tetraalkylammonium tetrafluoridochlorate(III) [cat][ClF4] ([cat]=[NEt3Me]+, [NEt4]+) is described. An acetonitrile solution of the corresponding alkylammonium chloride salt is fluorinated with diluted fluorine at low temperatures. The reaction proceeds via the [ClF2]? anion which is structurally characterized for the first time. The potential application of [ClF4]? salts as fluorinating agents is evaluated by the reaction with diphenyl disulfide, Ph2S2, to pentafluorosulfanyl benzene, PhSF5. The CN moieties in acetonitrile and [B(CN)4]? are transferred in CF3 groups. Exposure of carbon monoxide, CO, leads to the formation of carbonyl fluoride, COF2, and elemental gold is dissolved under the formation of tetrafluoridoaurate [AuF4]?.
- Kaupp, M.,Müller, R.,Pr?hm, P.,Riedel, S.,Schattenberg, C. J.,Schmid, J. R.,Sonnenberg, K.,Steinhauer, S.,Vo?nacker, P.
-
supporting information
p. 16002 - 16006
(2020/07/20)
-
- Connecting Organometallic Ni(III) and Ni(IV): Reactions of Carbon-Centered Radicals with High-Valent Organonickel Complexes
-
This paper describes the one-electron interconversions of isolable NiIII and NiIV complexes through their reactions with carbon-centered radicals (R?). First, model NiIII complexes are shown to react with alkyl and aryl radicals to afford NiIV products. Preliminary mechanistic studies implicate a pathway involving direct addition of a carbon-centered radical to the NiIII center. This is directly analogous to the known reactivity of NiII complexes with R?, a step that is commonly implicated in catalysis. Second, a NiIV-CH3 complex is shown to react with aryl and alkyl radicals to afford C-C bonds via a proposed SH2-type mechanism. This pathway is leveraged to enable challenging H3C-CF3 bond formation under mild conditions. Overall, these investigations suggest that NiII/III/IV sequences may be viable redox pathways in high-oxidation-state nickel catalysis.
- Bour, James R.,Ferguson, Devin M.,McClain, Edward J.,Kampf, Jeff W.,Sanford, Melanie S.
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supporting information
p. 8914 - 8920
(2019/06/13)
-
- Preparation method of 1,1,1-trifluoroethane
-
The invention provides a preparation method of 1,1,1-trifluoroethane (HFC-143a). The HFC-143a is prepared through liquid-phase fluoridation reaction under the presence of a composite catalyst by utilizing hydrogen fluoride (HF) and HCFC-142b as raw materials, the reaction temperature is 10-50 DEG C, preferably 10-40 DEG C, the weight ratio of the HF to the HCFC-142b is 1 to (4-5.5), preferably 1 to (4.5-5), the composite catalyst is a mixture of antimony halide and rare earth oxides, and rare earth metal is preferably neodymium or yttrium; the molar ratio of the antimony halide to the rare earth oxides is (20-200) to 1, preferably (20-150) to 1. According to the preparation method, the HFC-143a is prepared through liquid-phase fluoridation of the HF and the HCFC-142b, the conversion rate can reach 99.5% or above, the conversion rate of 98% or above can still be kept after continuous reaction for 1000 h, and the service life of the catalyst is prolonged.
- -
-
Paragraph 0021-0035
(2019/06/08)
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- A catalytic fluoride-rebound mechanism for C(sp3)-CF3 bond formation
-
The biological properties of trifluoromethyl compounds have led to their ubiquity in pharmaceuticals, yet their chemical properties have made their preparation a substantial challenge, necessitating innovative chemical solutions. We report the serendipitous discovery of a borane-catalyzed formal C(sp3)-CF3 reductive elimination from Au(III) that accesses these compounds by a distinct mechanism proceeding via fluoride abstraction, migratory insertion, and C-F reductive elimination to achieve a net C-C bond construction. The parent bis(trifluoromethyl)Au(III) complexes tolerate a surprising breadth of synthetic protocols, enabling the synthesis of complex organic derivatives without cleavage of the Au-C bond. This feature, combined with the fluoride-rebound mechanism, was translated into a protocol for the synthesis of 18F-radiolabeled aliphatic CF3-containing compounds, enabling the preparation of potential tracers for use in positron emission tomography.
- Levin, Mark D.,Chen, Tiffany Q.,Neubig, Megan E.,Hong, Cynthia M.,Theulier, Cyril A.,Kobylianskii, Ilia J.,Janabi, Mustafa,O'Neil, James P.,Toste, F. Dean
-
p. 1272 - 1275
(2017/06/30)
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- Silver-Catalyzed Decarboxylative Trifluoromethylation of Aliphatic Carboxylic Acids
-
The silver-catalyzed decarboxylative trifluoromethylation of aliphatic carboxylic acids is described. With AgNO3 as the catalyst and K2S2O8 as the oxidant, the reactions of aliphatic carboxylic acids with (bpy)C
- Tan, Xinqiang,Liu, Zhonglin,Shen, Haigen,Zhang, Pei,Zhang, Zhenzhen,Li, Chaozhong
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p. 12430 - 12433
(2017/09/25)
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- PROCESS FOR THE CO-PRODUCTION OF OF 2,3,3,3-TETRAFLUOROPROPENE AND 1,3,3,3-TETRAFLUOROPROPENE
-
The present invention provides a method of producing 2,3,3,3-tetrafluoropropene (HFO- 1234yf), wherein the method comprises two or more reaction steps, at least one of said reaction steps comprising the production of 1,3,3,3-tetrafluoropropene (HFO-1234ze) and/or one or more HFO-1234ze precursors from one or more HFO-1234yf precursors, wherein at least a portion of the HFO-1234ze is recovered.
- -
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Page/Page column 11
(2017/02/09)
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- PROCESS FOR PRODUCING FLUORINE-CONTAINING OLEFIN
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In the production of fluorine-containing olefins using a chlorine-containing alkane or a chlorine-containing alkene as a starting material, a process for producing a plurality of useful fluorine-containing olefins with high selectivity using the same raw material, the same equipment, and the same conditions is provided. The present invention provides a process for producing fluorine-containing olefins, the process comprising reacting a chlorine-containing compound represented by a specific formula and anhydrous hydrogen fluoride in the presence of oxidative gas and a fluorination catalyst, wherein the fluorination catalyst is a catalyst in which at least one metal element M selected from the group consisting of Group VIII and Group IX is present together with chromium. This production process can simultaneously produce two or more fluorine-containing olefin compounds, including HFO-1234yf and HFO-1234ze, with high selectivity.
- -
-
Paragraph 0090-0092; 0097
(2016/12/22)
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- Alternative synthetic routes to hydrofluoroolefins
-
A series of hydrofluoroolefins with -CF=CH2, -CH=CHF and -CH=CF2 groups were designed and prepared via various synthetic routes, including HX or BrF elimination, Wittig-type olefination or fluorination using SF4.
- Yagupolskii, Yu. L.,Pavlenko,Shelyazhenko,Filatov,Kremlev,Mushta,Gerus,Peng, Sheng,Petrov,Nappa, Mario
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p. 134 - 141
(2015/11/10)
-
- 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 0117; 0118
(2013/09/12)
-
- Rhodium-carbon bond energies in Tp′Rh(CNneopentyl)(CH2X)H: Quantifying stabilization effects in M-C bonds
-
A series of substituted methyl derivatives of the type Tp′ Rh(CNneopentyl)(CH2X)H (CH2X = CH2C(i - O)CH3, CH2Ci - CCH3, CH 2O-t-Bu, CH2CF3, CH2F, CHF 2) was synthesized either by photolysis of Tp′Rh(CNneopentyl) (PhNCNneopentyl) in neat CH3X or by exchange with the labile hydrocarbon in Tp′Rh(CNneopentyl)(n-pentyl)H or Tp′Rh(CNneopentyl) (CH3)H. Only a single product was observed in each case. Clean reductive elimination was observed for all compounds in C6D 6. Structures of these complexes and their corresponding chlorinated derivatives have been characterized by NMR spectroscopy, elemental analysis, and X-ray crystallography. Relative Rh-C bond energies are calculated using previously established kinetic techniques, and two separate linear correlations are observed versus known C-H bond strengths, one for the parent hydrocarbons, and one for the substituted hydrocarbons. Both correlations have slopes of 1.4, and are separated vertically by 7.5 kcal mol-1 (-CH2X above -CxHy). In addition, it is now clear that preferences for linear vs branched olefin insertion products in substituted derivatives can be predicted on the basis of the strengths of the β-C-H bonds. The DFT calculations of the metal-carbon bond strengths in these Rh-CH2X derivatives with α-substitution show a trend that is in good agreement with the experimental results.
- Jiao, Yunzhe,Evans, Meagan E.,Morris, James,Brennessel, William W.,Jones, William D.
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p. 6994 - 7004
(2013/06/27)
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- CATALYTIC FLUORINATION PROCESS OF MAKING HYDROHALOALKANE
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The present disclosure provides a fluorination process which involves reacting a hydrohaloalkene of the formula RfCCl=CH2 with HF in a reaction zone in the presence of a fluorination catalyst selected from the group consisting of TaF5 and TiF4 to produce a product mixture containing a hydrohaloalkane of the formula RfCFClCH3, wherein Rf is a perfluorinated alkyl group.
- -
-
Paragraph 0072; 0073
(2013/05/23)
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- PROCESS TO OBTAIN A TRIFLUOROMETHYLATING COMPOSITION
-
Process to obtain a trifluoromethylating composition which comprises the reaction between a copper (I) source and a base in the presence of a solvent and between the resulting cuprating reagent with fluoroform.
- -
-
Page/Page column 54-55
(2012/09/11)
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- Direct cupration of fluoroform
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We have found the first reaction of direct cupration of fluoroform, the most attractive CF3 source for the introduction of the trifluoromethyl group into organic molecules. Treatment of CuX (X = Cl, Br, I) with 2 equiv of MOR (M = K, Na) in DMF or NMP produces novel alkoxycuprates that readily react with CF3H at room temperature and atmospheric pressure to give CuCF3 derivatives. The CuCl and t-BuOK (1:2) combination provides best results, furnishing the CuCF3 product within seconds in nearly quantitative yield. As demonstrated, neither CF3- nor CF2 mediate the Cu-CF3 bond formation, which accounts for its remarkably high selectivity. The fluoroform-derived CuCF3 solutions can be efficiently stabilized with TREAT HF to produce CuCF 3 reagents that readily trifluoromethylate organic and inorganic electrophiles in the absence of additional ligands such as phenanthroline. A series of novel Cu(I) complexes have been structurally characterized, including K(DMF)[Cu(OBu-t)2] (1), Na(DMF)2[Cu(OBu-t)2] (2), [K8Cu6(OBu-t)12(DMF)8(I)] + I- (3), and [Cu4(CF3) 2(C(OBu-t)2)2(μ3-OBu-t) 2] (7).
- Zanardi, Alessandro,Novikov, Maxim A.,Martin, Eddy,Benet-Buchholz, Jordi,Grushin, Vladimir V.
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experimental part
p. 20901 - 20913
(2012/03/07)
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- γ-Alumina-supported boron trifluoride: Catalysis, radiotracer studies and computations
-
The irreversible adsorption of boron trifluoride on calcined γ-alumina and amorphous chromia, in both cases at room temperature, has been studied using [18F]-labelled BF3. Although the resulting γ-alumina surface has some catalytic activity for the room temperature fluorination by anhydrous HF of CH3CCl3 under static conditions, its activity is far lower than that of γ-alumina, which has been fluorinated with SF4, nominally at room temperature. A possible explanation for the observed behaviour is given.
- Klap?tke, Thomas M.,McMonagle, Fiona,Spence, Ronald R.,Winfield, John M.
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p. 1446 - 1453
(2008/09/19)
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- Method of making 1,1,1-trifluoroethane
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A process for producing 1,1,1-trifluoroethane (HFC-143a) which process comprises reacting hydrogen fluoride with vinylidene chloride along with one or more of 1,1,-dichloro-1-fluoroethane (HCFC-141b), 1-chloro-1,1-difluoroethane (HCFC-142b) and 1,1,1-trichloroethane (HCC-140a) in the presence of pentavalent antimony as a fluorination catalyst under conditions to produce 1,1,1-trifluoroethane (HFC-143a), generally in yields of 90% or more.
- -
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Page/Page column 4-6
(2008/06/13)
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- Noncatalytic manufacture of 1,1,3,3,3-pentafluoropropene from 1,1,1,3,3,3-hexafluoropropane
-
1,1,3,3,3-Pentafluoropropene (CF3CH═CF2, HFC-1225zc) can be produced by pyrolyzing 1,1,1,3,3,3-hexafluoropropane (CF3CH2CF3, HFC-236fa) in the absence of dehydrofluorination catalyst at temperatures of from about 700° C. to about 1000° C. and total pressures of about atmosphere pressure in an empty, tubular reactor, the interior surfaces of which comprise materials of construction resistant to hydrogen fluoride.
- -
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Page/Page column 4
(2008/06/13)
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- Porous aluminum fluoride
-
A porous aluminum fluoride on which SbClxF5-x (wherein x represents a numeral of 0 to 5) is supported, SbClxF5-x being obtainable by supporting SbCl, or the like on a porous aluminum fluoride and treating it with hydrogen fluoride. The resulting porous aluminum fluoride has a high activity as a fluorinating agent, a fluorination catalyst, or the like, is easy to handle, can be used for a flow-type reaction, and also can be used even at a high temperature.
- -
-
Page/Page column 4
(2008/06/13)
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- Method for producing 1,1,1-trifluoroethane
-
Process for the manufacture of 1,1,1-trifluoroethane (HFC-143a), according to which 1,1-difluoro-1-chloroethane (HCFC-142b) is subjected to a vapour-phase reaction with hydrogen fluoride (HF) in the presence of a hydrofluorination catalyst, in which process the molar ratio of the HCFC-142b introduced to the HF introduced into the vapour-phase reaction is greater than or equal to 1 and less than 1.3.
- -
-
Page/Page column 2
(2008/06/13)
-
- PROCESS FOR PRODUCTION OF 1,1,1,2-TETRAFLUOROETHANE AND/OR PENTAFLUOROETHANE AND APPLICATIONS OF THE SAME
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A process for producing high purity 1,1,1,2-tetrafluoroethane and/or pentafluoroethane by the step of purifying a crude product obtained by reacting trichloroethylene and/or tetrachloroethylene with hydrogen fluoride comprised of a main product including 1,1,1,2-tetrafluoroethane and/or pentafluoroethane, hydrogen fluoride as an azeotropic component with the main product, and impurity ingredients including at least an unsaturated compound, wherein said purifying step includes a step of bringing a mixture obtained by newly adding hydrogen fluoride into said crude product into contact with a fluorination catalyst in the vapor phase to reducing the content of the unsaturated compound contained in said crude product and a distillation step.
- -
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Page/Page column 11; 16
(2008/06/13)
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- Method of making difluoromethane, 1,1,1-trifluoroethane and 1,1-difluoroethane
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A process for the production of difluoromethane (HFC-32), 1,1,1-trifluoroethane (HFC-143a) and 1,1-difluoroethane (HFC-152a). In the process the following steps are employed: (a) providing a reaction vessel, (b) providing in the reaction vessel activated carbon impregnated with a strong Lewis acid fluorination catalys selected from halides of As, Sb, Al, TI, In, V, Nb, Ta, Ti, Zr and Hf, (c) activating the catalyst by passing through the activated carbon impregnated with a strong Lewis acid fluorination catalyst anhydrous hydrogen fluoride gas and chlorine gas, (d) contacting, in a vapor state in the reaction vessel containing the activated catalyst, hydrogen fluoride and one or more halogenated hydrocarbons selected from chlorofluoromethane, dichloromethane, 1,1,1-trichloroethane, vinyl chloride, 1,1-dichloroethylene, 1.2-dichloroethylene, 1,2-dichloroethane, and 1,1-dichloroethane for a time and at a temperature to produce a product stream comprising hydrofluorocarbon product(s) corresponding to the chlorinated hydrocarbon reactant(s), and one or more of hydrogen chloride, unreactacted chlorinated hydrocarbon reactant(s), under-fluorinated intermediates, and unreacted hydrogen fluoride, and (e) separating the hydrofluorocarbon product(s) from the product stream.
- -
-
Page/Page column 3
(2010/02/14)
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- PYROLYSIS PROCESS
-
The present invention relates to the pyrolysis of hydrochlorofluorocarbons to form fluoromonomers such as tetrafluoroethylene, the pyrolysis being carried out in a reaction zone lined with nickel and mechanically supported by a jacket of other corrosion resistant metal, the nickel lining providing an improved yield of valuable reaction products.
- -
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Page/Page column 4-5
(2008/06/13)
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- Method of making hydrofluorocarbons
-
A manufacturing process for making hydrofluorocarbons (HFCs), by reacting a hydrochlorocarbon and HF in a liquid phase catalytic reactor using a large mole ratio of HF to hydrochlorocarbon to minimize formation of high boiling by-products and improve HF consumption and hydrofluorocarbon yields.
- -
-
-
- Chloropentafluoroethane hydrodechlorination over tungsten carbides: Influence of surface stoichiometry
-
The relationship between the mode of activation and the catalytic properties of tungsten carbides was studied. Tungsten carbides were prepared by temperature-programmed reaction of WO3 with methane/hydrogen mixture and activated according to several thermal treatments by varying the temperature or the feed composition. The acid-base characteristic increased with the extent of decarburization of the surface. The surface properties of WC could be adjusted toward the formation of unsaturated compounds or alternatively toward hydrogenolysis compounds. However, the convergence observed in the temperature-programmed selectivity curves, whatever the initial C/W ratio, showed that the sample surfaces reach similar compositions by recarburization during reaction. Such acidic properties were involved in the dehydrohalogenation of chloropentafluoroethane responsible mainly for the formation of unsaturated compounds.
- Granger,Giraudon,Delannoy,Leclercq,Leclercq
-
p. 358 - 362
(2007/10/03)
-
- Synthesis of 1,1,1-trifluoroethane by fluorination of 1-chloro-1, 1-difluoroethane
-
The subject of the invention is the manufacture of 1,1,1-trifluoroethane by fluorination or 1-chloro-1,1-difluoroethane with anhydrous hydrofluoric acid. The reaction is carried out in the liquid phase and in the presence of a fluorination catalyst.
- -
-
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- Preparation of 1,1,1,2-tetrafluoroethane by the vapor-phase catalytic reaction of 1,1,1-trifluoro-2-chloroethane with anhydrous hydrogen fluoride
-
1,1,1,2-Tetrafluoroethane was prepared in 97% selectivity by the vapor-phase catalytic reaction of 1,1,1-trifluoro-2-chloroethane with anhydrous hydrogen fluoride (AHF) over a metal fluoride catalyst (CrF3 and CoF2) supported on porous aluminum fluoride (PAF). The relationship between the crystalline phase transition of porous aluminum fluoride and temperature from 100 to 640°C was investigated by X-ray diffraction.
- Quan, Heng-Dao,Yang, Hui-E,Li, Zhong,Ren, Jian-Zhang,Li, Hui-Li
-
p. 193 - 199
(2007/10/03)
-
- Gas-phase fluorination of fluoroethanes with elemental fluorine
-
Scientific basis for industrial gas-phase fluorination of fluoroethanes with elemental fluorine allowing production of higher-fluorinated fluoroethanes from lower-fluorinated compounds is developed. 2001 MAIK "Nauka/Interperiodica".
- Pashkevich,Mukhortov,Alekseev,Asovich,Rozhdestvenskaya
-
p. 1151 - 1155
(2007/10/03)
-
- Turnover Rate, Reaction Order, and Elementary Steps for the Hydrodechlorination of Chlorofluorocarbon Compounds on Palladium Catalysts
-
The rates of hydrodechlorination catalyzed by Pd supported on carbon for four chlorofluorocarbons spanned a range of 7 orders of magnitude. The rates scaled up to the bond strength of the carbon-chlorine bond for the gas-phase reactant. This finding demonstrates that the rate-determining step involves the scission of the C-Cl bond and suggests, through Polanyi and linear free-energy relationships, that rates for other compounds can be estimated if the C-Cl bond strength is known. The reaction orders for the most abundant products are approximately first-order for the chlorine-containing compound, half-order in H2, and inverse first-order in HCl. The reaction steps consistent with these orders include a rate-determining step involving the adsorption of the chlorofluorocarbon to a single site (which could be a single surface palladium atom) and equilibrated steps between gas-phase H2, gas-phase HCl, and adsorbed hydrogen and chlorine atoms. The rates on the supported catalysts are comparable to the ones reported before on a Pd foil, indicating that the support does not play a role in the reaction. The product distribution is independent of conversion, implying that the various products are formed from a single visit of the reactant on the surface and not from readsorption of gas-phase products. The four compounds studied were chloropentafluoroethane (CF3-CF2Cl), 2-chloro-1,1,1,2-tetrafluoroethane (CF3-CFClH), 1,1-dichlorotetrafluoroethane (CF3-CFCl2), and 1,1,1-trichloro-2,2,2-trifluoroethane (CF3-CCl3).
- Thompson,Rioux,Chen,Ribeiro
-
p. 3067 - 3077
(2007/10/03)
-
- Hydrodechlorination of 1,1-dichlorotetrafluoroethane over Pd/Al2O3 catalyst. Effect of hydrogen pressure and catalyst pretreatment
-
An alumina-supported palladium catalyst has been studied in CF3CFCl2 hydrodechlorination at 100°C using a static-circulation system. At higher partial pressures of H2, when the existence of the β-PdH phase is awaited, the reaction occurs similarly as at lower hydrogen pressures. This indicates that either the β-PdH formation does not have any special effect on active sites of this reaction, or the presence of CF3CFCl2 in the system inhibits this phase transformation. Various pretreatments of the 2 wt.% Pd/Al2O3 influence markedly its catalytic behavior. In particular, reoxidation and subsequent low temperature reduction of the catalyst, prereduced at 600°C, generates a very high activity, however, the selectivity towards CF3CFH2 is not much altered.
- Karpinski,D'Itri
-
p. 1421 - 1452
(2007/10/03)
-
- Spectroscopy of Hydrothermal Reactions 13. Kinetics and Mechanisms of Decarboxylation of Acetic Acid Derivatives at 100-260 °C under 275 bar
-
The rates and pathways of decarboxylation of acetic acid derivatives, RCO2H, and their Na+ salts, RCO2Na, which possess electron-withdrawing groups (R = CCl3-, CF3-, HOC(O)CH2-, NH2C(O)CH2-, CF3CH2-, NCCH2-, CH3C(O)-) were determined in H2O at 100-260 °C and a pressure of 275 bar. Simple conversion to RH + CO2 occurs in most cases, except that H2O appears to be a required reactant for the anions. Real-time FTIR spectroscopy was used to determine the rate of formation of CO2 in flow reactors constructed of 316 stainless steel (SS) and of titanium. With a few exceptions, the rate of decarboxylation is similar within the 95% confidence interval in 316 SS and Ti and the difference is smaller than that caused by R. Therefore, while wall effects/catalysis may exist in some cases, it plays a lesser role in the relative rates than the substituent R. The acid form of the keto derivatives decarboxylates more rapidly than the anionic form, whereas the reverse is true for the nonketo derivatives. In keeping with the greater role of H2O as a reactant, the entropy of activation for the anions is smaller or more negative than for the acids. A Taft plot of the decarboxylation rates suggests that the mechanistic details can be interpreted in terms of the various roles of R. Where R = HOC(O)CH2- and NH2C(O)CH2-, decarboxylation occurs faster than expected, probably because a cyclic transition state can exist. The rate is slower than expected for R = CF3-, perhaps because of stabilization of the acid by hyperconjugation. The mechanism of decarboxylation of acids of the remaining R groups is similar and the steric effect of R is somewhat more influential than its electron withdrawing power.
- Belsky,Maiella,Brill
-
p. 4253 - 4260
(2007/10/03)
-
- Hydrodechlorination of 1,1-dichlorotetrafluoroethane and dichlorodifluoromethane catalyzed by Pd on fluorinated aluminas: The role of support material
-
The gas phase hydrodechlorination of CF3CFCl2 to CF3CFH2 and CF2Cl2 to CF2H2 catalyzed by Pd supported on Al2O3, a series of fluorinated Al2O3, and AlF3 was investigated. A combination of reaction kinetics investigations and characterization by in situ FTIR spectroscopy has been performed. It has been found that for reactions involving CF3CFCl2, all catalysts exhibit a rapid and significant decrease in activity; however, little change in activity with time on stream occurs with CF2Cl2. FTIR investigations suggest the occurrence of direct reaction between the CFC and the support material, which results in the consumption of hydroxyl groups during the early stages of reaction. The effect of fluorination of support on catalytic behavior of Pd is discussed.
- Early, Kintu,Kovalchuk, Vladimir I.,Lonyi, Ferenc,Deshmukh, Subodh,D'Itri, Julie L.
-
p. 219 - 227
(2007/10/03)
-
- Generation of radical species in surface reactions of chlorohydrocarbons and chlorocarbons with fluorinated gallium(III) oxide or indium(III) oxide
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The reactions of C1 and C2 chlorohydrocarbons and chlorocarbons have been studied with the Lewis acid catalysts fluorinated gallium(III) oxide and fluorinated indium(III) oxide, respectively. Product analysis shows chlorine-for-fluorine exchange reactions together with the formation of 2-methylpropane and its chlorinated analogues 2-chloromethyl-1,3-dichloropropane and 2-chloromethyl-1,2,3-trichloropropane. Reactivities of the chlorohydrocarbon probe molecules show fluorinated gallium(III) oxide to be a stronger Lewis acid than fluorinated indium(III) oxide. The formation of the symmetrical butyl compounds is consistent with the generation of surface radical species and is also consistent with a 1,2-migration mechanism operating within radical moieties at the Lewis acid surface.
- Thomson
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p. 1881 - 1885
(2007/10/03)
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- Structure Insensitivity and Effect of Sulfur in the Reaction of Hydrodechlorination of 1,1-Dichlorotetrafluoroethane (CF3-CFCl2 ) over Pd Catalysts
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The kinetics of the hydrodechlorination of 1,1-dichlorotetrafluoroethane (CFC 114a) was studied on Pd(111), Pd(100), and a Pd foil at atmospheric pressure. The three products formed were CF3-CFH2 (HFC 134a), CF3-CFClH (HCFC 124), and CF3-CH3 (HFC 143a) with selectivities independent of conversion. The single crystals and foil (model catalysts) were studied in an apparatus that permitted the direct transfer of samples between a high pressure cell (1 atm) and an ultrahigh vacuum chamber. The reaction rates were measured in the temperature range of 350 to 470 K. The reaction is not sensitive to the structure of the catalyst, as indicated by the similar turnover rates for all catalysts tested. The reaction is inverse first order in the reaction product HCl on all samples. Sulfur adsorbed on the Pd surface depressed the rates of formation of 134a more strongly than the rates of 124 and 143a.
- Ribeiro,Gerken,Rupprechter,Somorjai,Kellner,Coulston,Manzer,Abrams
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p. 352 - 357
(2007/10/03)
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- Catalytic hydrodechlorination of 1,1-dichlorotetrafluoroethane by Pd/Al2O3
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Palladium supported on γ-alumina displays high activity for the hydrodechlorination of 1,1-dichlorotetrafluoroethane. High H2 partial pressures are needed to avoid deactivation, and steady state is obtained after ～5 h time on stream. Under these conditions (H2/CFC feed ratio = 20) the reaction is zero order in H2 partial pressure and positive (0.65) order in 1,1-dichlorotetrafluoroethane partial pressure. Three main products are formed: 1,1,1,2-tetrafluoroethane, 1-chloro-1,2,2,2-tetrafluoroethane, and 1,1,1-trifluoroethane, with approximately 85% selectivity toward the desired CF3CFH2. The apparent activation energies associated with the formation of each product range from 52 to 68 kJ/mol. All three major products have a nonzero rate of formation in the limit of zero conversion, the implication of which is that all are primary products. The kinetics results are consistent with a reaction mechanism involving a carbene intermediate. Variation of the temperature at which the catalyst is prereduced from 300 to 600°C results in an increase in particle size from 11-53 nm and in an increase in the hydrodechlorination TOF from 2.3 to 5.0 s-1.
- Karpinski, Zbigniew,Early, Kintu,D'Itri, Julie L.
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p. 378 - 386
(2007/10/03)
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- Effect of fluorination on thiol reactivities. Reaction of 2,2,2-trifluoroethanethiol on Mo(110)
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The reactions of 2,2,2-trifluoroethanethiol on Mo(110) were studied using temperature-programmed reaction, Auger electron, and infrared spectroscopies. Most significant is the evolution at 265 K of tritluoroethyl radical from a saturation coverage of CF3CH2S-. The strong coverage dependence for trifluoroethyl radical evolution and models depicting trifluoroethyl thiolate orientation at saturation coverage strongly suggest that surface crowding plays a significant role in radical formation. The stability of the radical and the steric inhibition to finding an adsorption site explain the evolution of the radical into the gas phase. C-S bond hydrogenolysis, yielding trifluoroethane, and defluorination, yielding difluoroethylene, are of nearly equal importance in the reaction of trifluoroethyl thiolate, whereas C-S bond hydrogenolysis of ethyl thiolate to form ethane predominates. The C-S bond hydrogenolysis pathway is similar for the two thiols, occurring at approximately 300 K in both cases. Dehydrogenation and alkene elimination from CH3CH2S- occur at approximately 340 K, as the supply of surface hydrogen is depleted through hydrogen recombination. In contrast, defluorination and fluoroalkene elimination from CF3CH2S- occur over a wide temperature range, 200-520 K. The formation of difluoroethylene on Mo(110) is nearly thermoneutral, due to the comparable strengths of the C-F and Mo-F bonds and the stability of difluoroethylene.
- Napier,Friend
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p. 8750 - 8757
(2007/10/02)
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- CH3CF3-nCln haloalkanes and CH2=CF2-nCln halo-olefins on γ-alumina catalysts: reactions, kinetics and adsorption
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The heterogeneously catalyzed reactions of the haloalkane, CH3CF(3-n)Cln, and halo-olefin, CH2=CF(2-n)Cl(n), series have been studied on a γ-alumina catalyst and the experimental results compared with calculated thermodynamic data.The main reactions occurring in this system can be explained by the following reaction paths: dehydrohalogenation, hydrohalogenation, F/Cl and Cl/F exchange with hydrogen halides.Dismutation reactions which are observed in other halocarbon series are unimportant in this system.A survey of the dominant reactions is given.In addition, the kinetic behaviour of CH3CF2Cl on the γ-alumina catalyst and the adsorption of various halocarbons have been investigated.The isosteric enthalpies of adsorption demonstrate that the interaction between the haloalkanes and the solid surface is more dominant than simple condensation. - Keywords: Chlorofluorocarbons; γ-Alumina catalysts; Heterogeneous catalysis; Kinetics; Adsorption; Enthalpy of adsorption
- Hess, A.,Kemnitz, E.
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- FLUORINATION OF ETHYLENE BY HIGHER FLUORIDES OF COBALT, MANGANESE, AND CERIUM
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Fluorination of ethylene by higher fluorides of metals with variable valence (CoF3, CeF4, MnF3) is studied.Temperature dependence of the contents of fluorinated products are obtained.The mechanism of formation of significant amounts of 1,1,1,2-tetrafluoroethane in the reaction involving CoF3 and oligomers in the reaction involving CeF4, is proposed.
- Asovich, V. S.,Kornilov, V. V.,Maksimov, B. N.
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- THERMAL AND THERMOOXIDATIVE STABILITY OF OZONE-SAFE FREONS
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The thermal stability of freons 134-a (CF3CH2F), 134 (CHF2CHF2), and 133-a (CF3CH2Cl) was studied experimentally by the pulsed adiabatic compression method.The conversion of the freons, beginning at a value of 0.0002, was determined from the carbon balance of the reaction products, calculated from the chromatographic data.The Arrhenius expressions for the total rate constants of thermal decomposition of the freons are presented.The intermediates of the thermal transformations of the freons were recorded by kinetic spectroscopy in the ultraviolet and visible regions.The UV spectrum of the carbene :CHCF3 with characteristic absorption maxima at λ 235 and 430 nm is described for the first time.
- Buravtsev, N. N.,Grigor'ev, A. S.,Kolbanovskii, Yu. A.,Ovsyannikov, A. A.
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p. 1880 - 1890
(2007/10/03)
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- FLUORINATION OF HYDROCARBONS BY THE HIGHER FLUORIDES OF COBALT, MANGANESE, AND CERIUM
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The fundamental possibility of producing partly fluorinated methanes, ethane, and propanes on an industrial scale was demonstrated with the higher fluorides of variable-valence metals as fluorinating agents.
- Asovich, V. S.,Kornilov, V. V.,Kostyaev, R. A.,Mel'nichenko, B. A.,Maruev, A. V.,Maksimov, B. N.
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p. 1284 - 1287
(2007/10/02)
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- DESORPTION OF REACTION PRODUCTS IN FLUORINATION OF ETHYLENE WITH COBALT TRIFLUORIDE
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Some macrokinetic relationships of ethylene fluorination with cobalt trifluoride have been investigated.Dependences of the degree of ethylene conversion on time of contact and temperature in reactors of batch and continuous operation have been studied.
- Kostyaev, R. A.,Pashkevich, D. S.
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p. 1426 - 1429
(2007/10/03)
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- Stabilisation of Palladium Metal Function of Oxide Supported Palladium Catalyst during the Hydrogenolysis of Chlorofluorocarbons
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Relative to Pd/C or Pd/γ-Al2O3 systems, γ-alumina supported Pd/ZnO catalyst enhanced catalytic activity and stability towards deactivation by halogen adsorption, during the hydrogenolysis of 1,1,2-trichlorotrifluoroethane.
- Sweetman, M. J.,Thomson, J.
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p. 2385 - 2386
(2007/10/02)
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- Room-temperature Catalytic Fluorination of C1 and C2 Chlorocarbons and Chlorohydrocarbons on Fluorinated Fe3O4 and Co3O4
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A study of the room-temperature reactions of a series of C1 and C2 chlorohydrocarbon and chlorocarbon substrate molecules with fluorinated iron(II,III) oxide and cobalt(II,III) oxide has been conducted.The results show that fluorinated iron(II,III) oxide exhibits an ability to incorporate fluorine into the following substrates in the order: Cl2C=CCl2 > H2C=CCl2 > CH3CCl3 > CHCl3 > CH2Cl2 > CH2ClCCl3 > CCl4 > CHCl2CHCl2.The fluorinated cobalt(II,III) oxide gave the reactivity series CHCl3 > CCl4 > H2C=CCl2 > CHCl2CHCl2 > CH2Cl2 > CH3CCl3 > CCl2CCl2 > CH2ClCl3.Reactions of C1 chlorohydrocarbon or chlorocarbon probe molecules with fluorinated Fe3O4 gave predominately C1 chlorofluorohydrocarbon and chlorofluorocarbon products, respectively, whereas fluorinated cobalt(II,III) oxide produced predominately C2 chlorofluorohydrocarbon and chlorofluorocarbons.For fluorinated Co3O4 the distribution of C2 products obtained from C1 chlorohydrocarbon precursor molecules is consistent with the formation of radical intermediates at strong Lewis acid surfaces.C2 chlorohydrocarbons exhibit a fluorine for chlorine (F-for-Cl) exchange reaction through the catalytic dehydrochlorination of the substrate to the alkenic intermediate.The F-for-Cl exchange process was dependent upon the ability of the substrate material to undergo dehydrochlorination; the inability of a substrate to undergo dehydrochlorination results in the fluorination process proceeding through the formation of chlorocarbon or chlorohydrocarbon radical intermediates.
- Thomson, James
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p. 3585 - 3590
(2007/10/02)
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- A novel trifluoromethylation method of saturated organic halides
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Treatment of methyl chlorodifluoroacetate with aliphatic halides in the presence of equivalent ammount of potassium fluoride, copper iodide and cadmium iodide at 120°C in HMPA for 8 h gave the corresponding trifluoromethyl derivatives in moderate yields.
- Chen, Qing-Yun,Duan, Jian-Xing
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p. 4241 - 4244
(2007/10/02)
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- Liquid-phase fluorination of 1,1,1-trichloroethane
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The reaction of HF with SbCl5 at 60 deg C and 1 MPa provides antimony mixed halides whose empirical formulae have been determined.The product is a mixture of SbClF4 and SbClF2 solvated by HF and its activity has been measured for the conversion of 1,1,1-trichloroethane (F140a) into mono- and difluorochloroethane (F141b and F142b).
- Brunet, S.,Batiot, C.,Barrault, J.,Blanchard, M.
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- Thermally and photochemically initiated radical chain decomposition of ketone-free methyl(trifluoromethyl)dioxirane
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Ketone-free solutions of methyl(trifluoromethyl)dioxirane (1) were obtained for the first time in several inert solvents, which enabled the study of the thermal and photochemical decompositions of dioxirane 1 in gas, solution, and matrix phases. Vacuum flash pyrolysis of dioxirane 1 afforded exclusively methyl trifluoroacetate (3a). Both gas- and liquid-phase photolyses and thermal liquid-phase decomposition of dioxirane 1 involve a radical chain process, initiated by attack of CH3 and CF3 radicals on dioxirane 1 to give α-alkoxy-substituted alkoxy radicals as intermediates; the latter are responsible for the production of esters 3a-d. Matrix-phase photolysis of dioxirane 1 led to methyl trifluoroacetate (3a) and 1,1,1 -trifluoroethane as main products, while gas-phase pyrolysis gave exclusively the ester 3a.
- Adam, Waldemar,Curci, Ruggero,Nu?ez, Maria Elena González,Mello, Rossella
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p. 7654 - 7658
(2007/10/02)
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- Fluorinated γ-Alumina. Catalytic Fluorination of 1,1,1-Trichloroethane at Ambient Temperature
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γ-Alumina, fluorinated with sulphur tetrafluoride followed by treatment with 1,1,1-trichloroethane, behaves as a catalyst for the room temperature fluorination of CH3CCl3 with anhydrous HF, giving a mixture of chlorofluorohydrocarbons.
- Thomson, James,Webb, Geoffrey,Winfield, John M.
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p. 323 - 324
(2007/10/02)
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