- Interconversion of Chlorofluorocarbons in Plasmas
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Chlorofluorocarbons undergo interconversion during destruction in an argon arc plasma, so that, for example, in the exhaust gas from destruction of CCl2F2, CClF3 is found to be the major residual ozone depleting substance: as electron capture detectors are 104 times less sensitive for CClF3, compared with CCl2F2, although these gases have the same ozone depleting potential, analysis of exhaust from destruction of chlorofluorocarbons is therefore not a trivial matter of determining only the level of input chlorofluorocarbon remaining.
- Deam, Rowan T.,Dayal, Austin R.,McAllister, Trevor,Mundy, Alan E.,Western, Robert J.,et al.
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Read Online
- A kinetic and mechanistic study of the Cl/F exchange reaction of CCl3F, CCl2F2, and CClF3 with prefluorided chromia
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A kinetic and mechanistic study of the Cl/F exchange reaction of CCl3F, CCl2F2, and CClF3 with prefluorided chromia was conducted. The activation energies of 53 and 54 kJ/mol for the simultaneous mono- and bi-exchange of the chlorine atoms of CCl3F with the surface fluoride ions of a prefluorided chromia were lower than that found for CCl4 (65 kJ/mol). This was due to the stronger C-F bond formed in CCl2F2 and CClF3, the C-Cl bond strengths in CCl4 and CCl3F were roughly the same. Mono-exchange occurred through a four-center intermediate in which the breaking of a C-Cl bond is compensated for by the formation of a C-F bond. Bi-exchange occurred by the CCl3F adsorption by the bonding of two Cl atoms to two appropriately spaced Cr ions on the CrF surface. Mono-exchange only was observed in the reaction of CCl2F2, the activation energy for which was 84 kJ/mol. This higher activation energy was due to the higher C-Cl (～ 318 kJ/mol) bond strength in CCl2F2 than in CCl3F (D(C-Cl) = 305 kJ/mol). The absence of the occurrence of bi-exchange producing CF4 was due to the instantaneous formation of CClF3 on the intermediate, which was adsorbed through two chlorine atom where bi-exchange should have been possible. No exchange of the C-Cl bond of CClF3 with the surface CrF was observed.
- Waugh,Farrokhnia,Sakakini
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Read Online
- IR multiphoton photochemistry of CF3Cl
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CF3Cl has been dissociated using the focused output of a CO2 TEA laser operating on the R(40) line of the 9.6 μm band.IR fluorescence has been observed for HF and HCl after irradiating mixtures of CF3Cl, HBr, and Ar, indicating the production of F as well as Cl.In addition, the laser-induced fluorescence spectrum of CF2 has been observed using a KrF laser (249 nm) to excite the CF2 A1B1 1A1 transition.A two-step dissociation mechanism in which CF3 and Cl are the primary products followed by the subsequent multiphoton absorption and dissociation of CF3 to produce CF2 and F is proposed.Evidence for secondary dissociation of CF3 has been demonstrated by observing CF2 in the infrared multiphoton dissociation of C2F6, which is known to produce CF3 at low fluence.Further evidence in support of two-step dissociation mechanism is given by analysis of stable products, fluence studies, and RRKM calculations.
- Horwitz, Alexander B.,Preses, Jack M.,Weston, Ralph E.,Flynn, George W.
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- CO2 Laser Induced Decomposition of CF3Cl: KInetics and Mechanisms
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The decomposition of CF3Cl by a CW CO2 laser has been studied over a range of temperatures, 1280-1740 K, and Arrhenius plots show two distinct regimes.At lower temperatures, C2F6 is produced with an activation energy of 86.0 kcal/mol.At high temperatures, C2F6 production is characterized by an activation energy of 54.0 kcal/mol, and now CF4 and CF2Cl2 are detected, being produced at equal rates with an activatuion energy of 86.2 kcal/mol.A reaction mechanism in agreement with these results is presented, and we obtain hitherto unreported activation energy values for the radical-molecule reactions of CF3 and CF2Cl with CF3Cl.
- Zitter, R. N.,Koster, D. F.,Choudhury, T. K.
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Read Online
- 2-Chloro-2,2-difluoracetamide (ClF2CC(O)NH2). Thermal decomposition, vapour infrared, mass spectrometry, low-temperature NMR, and theoretical studies. Solvent effects on conformational preferences
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Gas-phase thermal decomposition of 2-chloro-2,2-difluoracetamide (CDFA) was studied at temperatures between 270 and 290°C. The rate constant for the decomposition follows the Arrhenius equation. k = (5.5 ± 0.3) · 1016s-1 exp [-(104±4)kj mol-1/RT] Mass spectrometry was used to analyze the decomposition pattern of the title compound. The FT-IR spectrum of the vapour phase and the infrared spectra of CDFA in protic and aprotic solvents were recorded. Potential energy surfaces were studied by theoretical calculations performed at the density functional theory level (PBEPBE and B3LYP methods) using the 6-31G*, 6-31+G*, 6-311+G**, aug-cc-pVDZ, and aug-cc-pVTZ basis sets. CSIRO 2011.
- Iriarte, Ana G.,Cutin, Edgardo H.,Auergello, Gustavo A.
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experimental part
p. 1366 - 1372
(2012/01/19)
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- PROCESSES FOR PRODUCING AND COMPOSITIONS COMPRISING 2,3,3,3-TETRAFLUOROPROPENE AND/OR 1,2,3,3-TETRAFLUOROPROPENE
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A process is disclosed for making CF3CF=CH2 or mixtures thereof with CHF=CFCHF2. The process involves contacting CCI3CF2CF3 and optionally CCI2FCF2CCIF2 with H2 in the presence of a catalyst including a catalytically effective amount of palladium supported on a support of alumina, fluorided aluminaand/or aluminum fluoride, to produce a product mixture including CH2=CFCF3 (and when CCI2FCF2CCIF2 is present, CHF=CFCHF2); recovering CH2=CFCF3 or a mixture thereof with CHF=CFCHF2 from the product mixture; and optionally, separating at least a portion of any CHF=CFCHF2 in the product mixture from the CH2=CFCF3 in the product mixture. The mole ratio of H2 to the total of CCI3CF2CF3 and CCI2FCF2CCIF2 fed to the reaction zone is between about 1 :1 and about 5:1. The present invention also provides another process for making CH2=CFCF3 Or mixtures thereof with CHF=CFCHF2 This process involves (a) reacting CCI3CF2CF3 and optionally CCI2FCF2CCIF2 with H2 in the presence of a catalytically effective amount of a hydrogenation catalyst to form CH3CF2CF3 (and when CCI2FCF2CCIF2 is present, CH2FCF2CHF2); (b) dehydrofluorinating CH3CF2CF3 and optionally any CH2FCF2CHF2 from (a) to form a product mixture including CH2=CFCF3, and if CH2FCF2CHF2 is present, CHF=CFCHF2; (c) recovering CH2=CFCF3 or a mixture thereof with CHF=CFCHF2 from the product mixture formed in (b); and optionally (d) separating at least a portion of any CHF=CFCHF2 in the product mixture formed in (b) from the CH2=CFCF3 in the product mixture formed in (b). The present invention also provides compositions involving CH2=CFCF3 and/or CHF=CFCHF2, including compositions useful as refrigerants, foam blowing agents, cleaning agents and aerosols and azeotropic compositions involving (a) CF2HCF=CFH and (b) HF.
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Page/Page column 17
(2008/12/05)
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- Catalytical production processes for making hydrohalopropanes and hydrofluorobutanes
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A process is disclosed for making hydrohalopropanes or hydrofluorobutanes. The process involves reacting a hydrofluoromethane with a fluoroolefin in the presence of an aluminum catalyst to produce a hydrohalopropane or a hydrofluorobutane. The hydrofluoromethane is CH2F2 or CH3F. The fluoroolefin is CF2═CF2, ClFC═CF2, or CF3CF═CF2.
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Page/Page column 3
(2008/06/13)
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- Nitrogen trifluoride as an oxidative co-reagent in high temperature vapor phase hydrofluorinations
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Nitrogen trifluoride (NF3) has proven to be a useful additive in high temperature vapor phase hydrofluorination reactions of chlorocarbons. The activity of chromium-based catalysts is maintained by introducing a co-stream of NF3 into the reagent chlorocarbon and HF stream. NF3 is a desirable additive instead of O2 as there is no water generation due to its use.
- Belter, Randolph K.,Sweval, Mark S.,Iikubo, Yuichi
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p. 816 - 820
(2008/03/27)
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- CONVERSION OF FLUOROCARBONS
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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.
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Page column 7-10
(2008/06/13)
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- Materials and methods for the conversion of hydrofluorocarbons
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Methods and materials are disclosed for the recovery of valuable hydrofluorocarbons and subsequent conversion to environmentally inert compounds. More specifically methods and materials are provided for recovering hydrofluorocarbons such as HFC-227, HFC-236, HFC-245, HFC-125, HFC-134, HFC-143, HFC-152, HFC-32, HFC-23 and their respective isomers. Processes are provided for converting hydrofluorocarbons such as these to fluoromonomer precursors such as CFC-217, CFC-216, CFC-215, CFC-115, CFC-114, CFC-113, CFC-112, HCFC-22, CFC-12, CFC-13 and their respective isomers. Materials, methods and schemes are provided for the conversion of these fluoromonomer precursors to fluoromonomers such as HFP, PFP, TFP, TFE, and VDF.
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- Kinetics of tetrachloromethane fluorination by hydrogen fluoride in the presence of antimony pentachloride
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Contradictory information concerning the kinetics of tetrachloromethane fluorination by anhydrous hydrogen fluoride in the presence of antimony pentachloride has been explained. The present studies were performed using a stainless steel autoclave. The exchange of the first chlorine atom was carried out in the temperature range of 35-95°C, with the molar ratio of HF/CCl4 varied within the range of 1.2-1.7 and at a constant molar ratio of SbCl5/Cl2 equal to 1.9. The degree of conversion of CCl4 to CCl3F and the reaction rate constant as a function of temperature fit to an Arrhenius straight line. The Arrhenius constants (pre-exponential factor) and the activation energy were determined. Studies concerning the exchange of the second chlorine atom, i.e. the conversion of CCl3F to CCl2F2 have been performed. The results of kinetic investigations were created in the same way. Based on these results it was found that the Arrhenius equation is fulfilled also in the second stage of the fluorination. The same slope of the straight lines confirms that the fluorination stages proceed according to the same mechanism with the same activation energy but with different pre-exponential factors. Several kinetic problems associated with the performance of the reactor can be solved on the basis of the equations derived. However, knowledge of CCl4 conversion as a function of time, temperature, catalyst concentration and the type of the reaction is required for this purpose. Such calculations enable the selection of the optimal process parameters.
- Meissner, Egbert,Milchert, Eugeniusz
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- The radiation chemistry of acyclic hydrofluoro and perhalogenated ether and hydrocarbon compounds
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The radiolytic stability of some hydrofluoroethers and hydrofluorocarbons was investigated and compared with those of perfluoropolyethers (PFPEs) and the CCl2FCClF2 (CFC 113). The experimental results indicate that stability depends mainly on the relative abundance of hydrogen atoms in the molecule; however, a significant role is played also by the chemical structure (i.e. the relative positions of the hydrogen atoms in the molecule). As a result, molecules containing hydrogen atoms as -OCF2H chain ends show a higher stability compared with the other hydrofluoro compounds. Based on the analysis of the end products and on the nature of radicals detected by EPR, radiolysis mechanisms are proposed and discussed. Due to their high dipole moments the hydrofluoro compounds and CCl2FCClF2 degrade mainly through an ionic mechanism.
- Marchionni, Giuseppe,Guarda,Buttafava,Faucitano, Antonio
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p. 153 - 162
(2007/10/03)
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- 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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- Liquid phase fluorination process and fluorinated organic products resulting therefrom
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In an improved process and plant for carrying out liquid phase fluorination in the presence of a catalyst, consisting in reacting hydrofluoric acid and an organic starting material in a reaction zone, and in separating, in a separating zone, reactional mixture and at least one light fraction containing the desired fluorinated organic products and at least a first part of the sub-fluorinated organic products formed, and a heavy fraction that includes the remainder of the sub-fluorinated organic products formed, and further comprising partial condensation of the said light fraction in order to obtain a gaseous phase containing the desired fluorinated organic products and a liquid phase containing said first part of the said sub-fluorinated organic products, said heavy fraction being returned to said reaction zone and said liquid phase being returned as a reflux to the top of the separation zone, intermediate recovery is carried out at, or in the proximity of, the lower portion of said separation zone.
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- Selective fluorination of dichloromethane by highest oxidation state transition-metal oxide fluorides
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In contrast to the reactivity of high oxidation state binary transition-metal fluorides with organic solvents, many transition-metal oxide fluorides do not react with CH2Cl2. Only the highest oxidation state species react, at temperatures below room temperature, via Cl-F exchange with > 90% selectivity, affording unstable high oxidation state chloro complexes which decompose to chlorine and lower oxidation state species.
- Holloway, John H.,Hope, Eric G.,Townson, Paul J.,Powell, Richard L.
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p. 105 - 107
(2007/10/03)
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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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- The reactions of xenon difluoride with "inert" solvents
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The reactions of XeF2 with a variety of organic solvents are dscribed.XeF2 is found to undergo both hydrogen-and chlorine-fluorine exchange over a relatively short timescale with chloroform, dichloromethane and dibromomethane.XeF2 reacts very slowly with tetrachloromethane and fluorotrichloromethane, although the addition of a catalitic amount of Hf increases the rate of reaction considerably.XeF2 dissolves in acetonitrile with negligible reaction to the extent of 2.25 mol kg-1.
- Dukat, Wolfgang W.,Holloway, John H.,Hope, Eric G.,Townson, Paul J.,Powell, Richard L.
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p. 293 - 296
(2007/10/02)
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- Synthesis of functionalized polyfluoroalkyl hypochlorites and fluoroxy compounds and their reactions with some fluoroalkenes
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Several new polyfluoroalkyl hypochlorites and fluoroxy compounds containing Cl, H and Br in the alkyl group have been prepared and characterized by 19F NMR, 1H NMR and IR spectroscopies and by their reactions with fluoroalkenes to produce new polyfluoroethers.The novel compounds are prepared by the CsF-catalyzed addition of F2 or ClF to the C=O bond in CF3C(O)CF2Cl, ClCF2C(O)CF2Cl, and their derivatives HCF2C(O)CF3 and HCF2C(O)CF2Cl.Compounds containing an α-CF3 group exhibit enhanced thermal stability.New fluoroxy compounds and hypochlorites have also been prepared from the acid fluorides CF3-CFX-C(O)F (X = Cl, Br), which are obtained by the ring-opening reaction of hexafluoropropene oxide with (CH3)3SiCl, LiBr and (C2H5)3SiBr.These -OX compounds behave similarly to previously known materials with two α-F atoms, decomposing quickly at room temperature to COF2 and haloalkanes.
- Randolph, Bruce B.,DesMarteau, Darryl D.
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p. 129 - 150
(2007/10/02)
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- Electron Attachment Processes in Molecular Aggregates
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Reactions in negatively charged clusters following resonant electron attachment have been studied in a supersonic beam experiment.The results are discussed with respect to the correspondent processes from single molecules in the gas phase and from condensed molecules.It is shown that electron capture by oxygen clusters allows the population of electronic states in O2(-) not accesible in the single-electron-molecule frame of reference (violation of the ?(-) selection rule).Clusters composed of O2/CF2Cl2 yield ionic products composed of both constituents.They are generated along a complex scattering process within the ionized aggregate.The resonance profiles of their ion yields contain information on their genesis, i.e. the initial step of electron capture by the electrophore in the cluster.Since these reactions occur predominantly at low energies, sometimes at zero eV, we consider them as highly relevant in any environment (gaseous or condensed) where low energy electrons are present.Clusters / Elementary Reactions / Energy Transfer / Molecular Beams / Molecular Interactions
- Hashemi, Reza,Meinke, Martina,Jaffke, Thomas,Illenberger, Eugen
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p. 440 - 447
(2007/10/02)
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- INFRARED LASER INDUCED DECOMPOSITION OF HEXAFLUOROBENZENE AND SOME MONOSUBSTITUTED DERIVATIVES. INTERMEDIACY OF THE PENTAFLUOROPHENYL RADICAL.
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The infrared multiphoton laser induced reactions of hexafluorobenzene and related pentafluoro analogues (pentafluorobenzene, pentafluorochlorobenzene, pentafluorobromobenzene, and pentafluoroiodobenzene) have been investigated using a CO2 TEA laser.The study was carried out in order to define the decomposition products and to attempt to clarify their mode of formation.Thus, the products (relative yield, percent) of the irradiation of C6F6 (1027.3 cm-1; 0.73 J/cm2; 10 pulses; 25percent decomposition) were C2F4(64), C6F5CF3(28), C2F6(7), CF4(1) and that for C6F5H (949.4 cm-1; 0.80 J/cm2; 10 pulses; 25percent decomposition) was C2F4 and C6F5CF3.Increasing the number of pulses in the reaction with C6F6 decreased the amount of C2F4 and increased the amount of C6F5CF3 and C2F6 indicating secundary and tertiary reactions.Addition of halogen (X2, X = Cl, Br) to these reactions caused different products to be formed.Thus, the irradiation of a C6F6/Cl2 mixture (7.4/7 Torr; 1027.3 cm-1; 0.7 J/cm2; 35 pulses; 35percent reaction) afforded C6F5Cl(46); CF3Cl(24) and CF2Cl2(30).Irradiation of C6F5H/X2 mixtures afforded mainly C6F5X + HX.For example C6F5H/Br2 (10/40 Torr; 949.4 cm-1; 0.93 J/cm2; 10 pulses; 10percent reaction) gave C6F5Br and HBr exclusively.Irradiation of C6F5-X (X = Cl, Br, I) (977.2 cm-1; ca. 0.74 J/cm2; 200 pulses; 39-74percent reaction) gave C6F6 and a minor amount of decafluorobiphenyl , a radical combination product of the pentafluorophenyl radical (C6F5.).Increasing the fluence in these reactions gave similar products in most cases but in some instances increased the amount of C2F4 formed.The reactions and product distribution of the hydrogen substituted derivative (C6F5H) was examined in the presence of Br2 as a function of laser fluence and halogen concentration.It was found that the threshold for C6F5H decomposition was higher for the reaction involving Br2 (as compared with the reaction involving Cl2 or neat C6F5H).The presence of Br2 also decreased the amount of C6F5H that was decomposed, indicating a quenching process.The decomposition path with the lowest activation energie for these molecules is thought to be C6F5X -> C6F5. + X. and was accessible using a laser pulse with a fluence as low as 0.7 J/cm2.Using a higher laser fluence (ca. 1.2 J/cm2) di- and triatomic radicals were defined by spectroscopic identification of the and :CF2 species.These reactions are discussed in light of the formation of the C6F5. radical during a primary, laser induced, process.Subsequent decomposition to smaller fragments, combination with other radicals or scavenging by added reagents also takes place depending on the reaction conditions.
- Watanabe, Akio,Koga, Yoshinori,Sugawara, Ko-ichi,Takeo, Harutoshi,Fukuda, Kenzo,Matsumura, Chi
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p. 463 - 469
(2007/10/02)
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- Electron Affinity of Chlorine Dioxide
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The flowing afterglow technique was used to determine the electron affinity of chlorine dioxide.A value of 2.37+/-0.10 eV was found bracketing between the electron affinities of HS and SF4 as a lower limit and that of NO2 as an upper limit.This value is in excellent agreement with 2.32 eV predicted from a simple thermodynamic cycle involving the reduction potential of the ClO2/ClO2- couple and a Gibbs hydration energy identical with that of SO2-.
- Babcock, L. M.,Pentecost, T.,Koppenol, W. H.
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p. 8126 - 8127
(2007/10/02)
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- NEW SYNTHESIS OF POLYCHLORO(TRIFLUOROMETHYL)BENZENES AND HIGHLY STRAINED POLYCHLORO(TRICHLOROMETHYL)BENZENES
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Several polychloro(trifluoromethyl)benzenes have been prepared by treatment of the corresponding polychlorobenzenes with CCl3F and AlCl3.The resulting trifluoromethyl derivatives, by reaction with the same inorganic halide in CS2, give their trichloromethyl analogues.
- Riera, Juan,Castaner, Juan,Carilla, Jose,Robert, Ana
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p. 3825 - 3828
(2007/10/02)
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- Etude cinetique et analytique de l'oxydation par l'air du difluorochlorobromomethane entre 400 et 800 deg C, coefficient negatif de temperature de la reaction
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Kinetic and analitical study of the difluorochlorobromomethane oxidation is operated by the pyromether method between 400 and 800 deg C.The reaction is followed as a function of time by measuring the pressure variation.Among the formed products, some are analyzed by infrared spectroscopy (CO2, CF2O, CF2Cl2, CF2ClOX and SiF4).The important fact of the study lies in the appearance of a negative temperature coefficient for the reaction beyond 800 deg C, while it appears beyond 670 deg C for mixture of air and CF3Br.CF2ClBr seems to be a better fire extinguishant than CF3Br.This could be explained by the great yield of CF2Cl2 obtained during the CF2ClBr oxidation reaction.CF2Cl2 tends to be oxidized into CF2O more easily than CF2O into CO2.More stable than CF2ClBr and CF3Br, CF2Cl2 should be a better fire extinguishant.However it is forbidden to use it in France because of its toxicity.Moreover the experimental results corroborate only one type of process for the CO2 formation reaction : FCO3. -> CO2 + FO.; whose Arrhenius average activation energy is 115 +/- 5 kJ * mol-1.
- Antonik, Stanislas
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p. 837 - 843
(2007/10/02)
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- Thiocarbonyl Fluoride in the Solvent System Hydrogen Fluoride: Preparation and Reactions of Halogenated Thiocarbenium Ions
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Solvolysis of thiocarbonyl fluorides 1b, c in HF/SbF5 or FSO3H/SbF5 yields dithietane-2-ylium ions 2b, c, respectively.Reactions of 2b, c with the base F in the solvent system HF give the dithietanes 3b, c.The acidity dependance of the formation of 2b, c is demonstrated by gradation of the acidic strength with NbF5 and F(1-).The existence of thioacylium ions 5b, c in solutions of extremely high acidity is concluded from NMR spectroscopic data.The results of the solvolysis reactions are confirmed by thioacylation of the aromatic compounds 6a-d in the HF system leading to trifluoromethyl dithiobenzoates 7a-d.Among the corresponding carbonyl fluorides only 4 exhibits comparable basic properties in superacids.
- Haas, Alois,Wanzke, Wolfgang
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p. 429 - 434
(2007/10/02)
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- Infrared Multiphoton-Induced Concerted :CF2 Elimination in Octafluorocyclopentene by a Pulsed CO2 Laser
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On infrared multiphoton excitation, octafluorocyclopentene (OFCP) undergoes a ring-opening reaction to give difluorocarbene and hexafluorobutadiene as unstable primary products which undergo further reactions; the former dimerizes to tetrafluoroethylene, and the latter isomerizes to its thermodynamically stable cyclic isomer.The multiphoton dissociation (MPD) yield of OFCP shows a strong fluence dependence, with a threshold of 0.3 J/cm2 for the 10R(32) line of the CO2 laser for inducing the reaction.Two characteristic peaks in the MPD spectra have been observed, both red-shifted from the ν20 ring deformation mode absorption peak of OFCP.Increase in pressure of OFCP or foreign gas addition has shown to deteriorate the MPD yield.
- Chowdhury, Pradyot K.,RAO, K. V. S. Rama,Mittal, J. P.
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p. 2877 - 2882
(2007/10/02)
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- SUBSTITUTIVE AROMATIC FLUORINATION WITH CHLORINE PENTAFLUORIDE
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In contrast to limited substitutive fluorination of aromatics with halogen fluorides such as ClF, ClF3, BrF3 and IF5, fluorination is the predominant reaction path with ClF5.Under non-catalytic liquid phase conditions, benzene was converted to fluorobenzene (54percent yield) and chlorobenzene (37percent yield), respectively.For a heterocyclic substrate, i.e. 2,4,6-trifluoropyrimidine, sunstitutive fluorination predominated over chlorination.Three possible fluorination mechanisms are discussed.A transition complex of ClF5 with benzene is favored.Enhanced exchange fluorination of CCl4 was effected with ClF5 (CF2Cl2 >> CFCl3 > CF3Cl) as compared with ClF3 (CFCl3 >> CF2Cl2)
- Boudakian, Max M.,Hyde, Gene A.
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p. 435 - 446
(2007/10/02)
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- Photochemistry of Anhydrides. Part 6.-Photolysis of Chlorodifluoroacetic Anhydride, (CF2ClCO)2O
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The photolysis of the vapour of chlorodifluoroacetic anhydride, (CF2ClCO)2O, has been studied over the range 19-201 deg C using 248 nm radiation.Quantum yields of the products CO, CO2, CF2ClCF2Cl and CF2Cl2 were measured with and without added quencher.The effective primary process is which is followed by .The ratio kc/kd is equal to 7.6 at 19 deg C and 4.7 at 201 deg C, both independent of pressure of anhydride and of perfluoromethylcyclohexane added as a quencher.The reactions of CF2Cl radicals from various photolytic sources are compared.
- Watkins, Paul E.,Whittle, Eric
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p. 2323 - 2330
(2007/10/02)
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- Reactivity of Fluorochloromethanes with Desert Sands
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Desert sand reactivity with halocarbons like CCl3F (F11), CCl2F2 (F12) and CHCl2F (F21) has been proved.Reactivity increases in the sense: F12 F21 F11 and is favoured by temperature and short activation of samples at 673 K.For F11, the main reaction products are CCl4 and COCl2, but some transformation to F12 has been observed too.An influence of the desert sand origin (i. e. of its phase composition) has been also found. - X-ray photoelectron spectra of samples after reaction show the presence of F and Cl on their surface, mainly as calcium halides, and in direct proportionality with reactivity.
- Benzoni, L.,Garbassi, F.
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p. 379 - 382
(2007/10/02)
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- HALOGEN FLUOROSULFATE REACTIONS WITH FLUOROCARBONS
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The scope of the reaction of simple fluorocarbon halides with chlorine fluorosulfate and mixtures of chlorine and bromine fluorosulfate to produce RfOSO2F compounds has been investigated.It is shown that in many cases even primary chlorine in -CF2Cl groups can be replaced by -OSO2F.Primary bromine or iodine in -CF2X are more readily replaced.The mechanism of this replacement reaction has been established by the isolation of the metastable iodine III intermediate RfI(OSO2F)2.Neither secondary chlorine nor bromine in -CFX- groups is affected.With the secondary iodide, i-C3F7I, the salt + - is formed.Furthermore, it has been found that ClOSO2F is capable of converting fluorocarbon acids or their derivatives into fluorocarbon halides.A combination of these two ClOSO2F reactions with the known conversion of RfCF2OSO2F to the corresponding fluorocarbon acid offers a novel, high yield chain shortening reaction for the otherwise unreactive fluorocarbon halides according to:
- Shack, Carl J.,Christe, K. O.
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- Synthesis of Perfluoroalkyl Trifluoromethanesulfonates from Perfluoroalkyl Halides. Substitutive Electrophilic Dehalogenation with Chlorine(I) and Bromine(I) Trifluoromethanesulfonates
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The reactions of chlorine(I) and bromine(I) trifluoromethanesulfonates with a variety of perfluoroalkyl halides are reported.The reactions form Br2, Cl2, or BrCl and the corresponding trifluoromethanesulfonate derivatives of the alkyls in good yields.Twelve new esters are reported and characterized.An SEi-type mechanism for the reactions is proposed with complete retention of configuration by the alkyl on substitution.
- Katsuhara, Yutaka,DesMarteau, Darryl D.
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p. 2681 - 2686
(2007/10/02)
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- DISPROPORTIONATION OF CF3Cl CATALYZED BY AL2O3*Cr2O3
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A mixed oxide of Al2O3 and Cr2O3 (Al2O3*Cr2O3) showed catalytic activity higher than that of Al2O3 or Cr2O3 in the disproportionation of CF3Cl.Maximum conversion (>30percent) was obtained when the reaction was carried out over the mixed oxide (atomic ratio of Cr/Al:1/9) at 450 deg C.
- Okazaki, Susumu,Eriguchi, Hideki
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p. 891 - 894
(2007/10/02)
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