- Deuterium kinetic isotope effects in the gas-phase SN2 reactions of solvated fluoride ions with methyl halides
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Rate constants and deuterium kinetic isotope effects (KIEs) are measured for gas-phase nucleophilic substitution (SN2) reactions of solvated fluoride ions of F-(methanol) + CH3X (X = Br, I), F -(isopropyl alcohol) + CH3I, and F-hydrogen fluoride) + CH3I at 300 K. The isotope effects are determined as the rate constant ratio kH/kD for specifically deuterated reactants, that is, methanol (CH3OH, CD3OH, CH 3OD, and CD3OD), isopropyl alcohol (i-C3H 7OH and i-C3H7OD), hydrogen fluoride (HF and DF), and methyl halides (CH3X and CD3X). The data reveal identical trends to those previously observed for F-(water) + CH 3X (O'Hair, R. A. J.; Davico, G. E.; Hacaloglu, J.; Dang, T. T.; DePuy, C. H.; Bierbaum, V. M. J. Am. Chem. Soc. 1994, 116, 3609). The S N2 reactivities decrease as reaction exothermicity decreases (CH 3I > CH3Br > CH3Cl) and as the nucleophile is solvated. Moderate inverse kinetic isotope effects (k H/kD N2 transition-state structure and bonding interactions analogous to those in the F -(H2O) + CH3X system.
- Kato, Shuji,Hacaloglu, Jale,Davico, Gustavo E.,DePuy, Charles H.,Bierbaum, Veronica M.
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- A Theoretical Study of Fluorine Atom and Fluoride Ion Attack on Methane and Silane
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We have performed MNDO and ab initio calculations for reactions of fluorine atom attack on methane and silane and, in addition, fluoride ion attack on the same molecules in the case of MNDO.We modeled both substitution and abstraction reactions in each case.Results were compared with experimental data, where available.Comparisons show that MNDO usually does as well as the ab initio methods in reproducing experimental values for ΔE's of these reactions, but MNDO predicts activation barriers too high in most cases.Nevertheless, MNDO does qualitatively agree with the ab initio result that, while carbon undergoes abstraction much more easily than substitution, silicon can undergo either substitution or abstraction quite easily.The analysis in the case of fluoride ion attack on silane is complicated by the predicted ease of formation of a stable trigonal-bipyramidal intermediate.
- Davis, Larry ,P.,Burggraf, Larry, W.,Gordon, Mark, S.,Baldridge, Kim, K.
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- Synthesis and characterization of tetramethylammonium trifluorosulfate
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[Me4N]+[SO2F3]-, the first example of a [SO2F3]- salt, has been prepared from Me4NF and SO2F2. The colorless, microcrystalline solid was characterized by its infrared and Raman spectra. The trigonal bipyramidal structure of C2v symmetry of the [SO 2F3]- anion is predicted by ab initio calculations. Two oxygen atoms with d(SO)=143.2pm and one fluorine atom with d(SF)=157.9pm occupy the equatorial plane. The two fluorine atoms in the axial position with d(SF)=168.5pm are repulsed by the two oxygen atoms forming a bent axis with (FaxSFax)=165.2°. Copyright
- Hohenstein, Christian,Kadzimirsz, Daniel,Ludwig, Ralf,Kornath, Andreas
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- Rates of processes initiated by pulsed laser production of F atoms in the presence of HCl, CH4, and CF3H
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Time-resolved vibrational chemiluminescence from HF has been recorded following the production of F atoms by the pulsed laser photolysis (λ = 266 nm) of F2 in the presence of HCl, CH4, and CF3H. In the first two cases, experiments have been conducted by observing emission from HF(ν = 3) at four temperatures from 295 to 139 K. Rate constants have been determined over this range of temperature for the reactions of F atoms with HCl and CH4 and of CH3 radicals with F2, and for the relaxation of HF(ν = 3) by HCl and CH4. The reaction of F atoms with CF3H is slower than those with HCl and CH4 and measurements on the emission from HF(ν = 2) have been used to infer rate constants for reaction and relaxation only at 295 K.
- Moore,Smith,Stewart
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Read Online
- Observation of the Nucleophilic Displacement (SN2) Reaction F-+CH3Br→CH3F + Br- Induced by Dissociative Electron Capture in Binary van der Waals Clusters
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We report on the SN2 reaction F- + CH3Br→FCH3 + Br- in binary clusters composed of CH3Br and C2F6 in a crossed electron/molecular beam experiment. The reaction is induced by resonance dissociative electron attachment to the C2F6 component where the nucleophile F- is generated at an energy (around 3.8 eV) where CH3Br does not capture electrons to form Br-. The results indicate that the cross section for the SN2 reaction is independent of the total excess energy which can be varied between 1.7 and 5 eV in the present system. VCH Verlagsgesellschaft mbH 1997.
- Lehmann, Lars,Matejcik, Stefan,Illenberger, Eugen
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- Kinetic Energy and Temperature Dependences for the Reaction of F(1-) with Halogenated Methanes: Experiment and Theory
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Rate constants have been measured as a function of average kinetic energy at several teperatures for the reaction of F(1-) with CH3Cl, CH3Br, and CH3I.The rate constants at low energy approach but are not equal to the collision limiting value.The rate constants for all three reactions decrease slowly with increasing average kinetic energy for enrgies below 0.2 to 0.3 eV.At 0.2 to 0.3 eV, a break occurs in the slopes of the energy dependence curves.Above these energies the rate constants decrease more rapidly with increasing energy.Trajectory calculations that include a probability function which is dependent upon collision angle were performed in order to examine the effects of orientation on the reactions.The calculations were fitted to the low energy portion of the experimental data.A more severe orientation requirement is found for the lighter halides.The energies at which the breaks occur in the experimental curves are reproduced by the calculations.These energies correspond to the energies at which the hard sphere collision diameter of the colliding partners is equal to the capture radius.
- Su, Timothy,Morris, Robert A.,Viggiano, A. A.,Paulson, John F.
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- Temperature dependences of the rate constants and branching ratios for the reactions of F-(H2O)0-5 with CH3Br
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The effects of solvation, isotopic substitution, and temperature on the reactions of F-(H2O)n=0-5 with CH3Br have been studied. The reaction of n = 0 produces Br- as the exclusive ionic product and has a rate which is fast, approaching the collision rate, with a slight negative temperature dependence of T-0.9±0.1. The reaction of n = 1 is a factor of 3 slower with a slightly larger negative temperature dependence, T-1.1±0.05. The main ionic product is Br-, with smaller amounts of Br-(H2O) also formed. Substituting D2O for H2O causes the n = 1 rate constant to increase slightly. The n = 2 reaction has a much slower rate and produces three ionic products: Br-, Br-(H2O), and F-(H2O)2(CH3Br). The n = 3 reaction is immeasurably slow. The rate constants for the n = 4 and 5 reactions are greater than those for the n = 3 reaction. The ionic products of these reactions are F-(H2O)3 and F-(H2O)4, respectively.
- Seeley, John V.,Morris, Robert A.,Viggiano
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- Photolysis of Fluorine Molecules Trapped in Solid Methane at 15 K: Evidence of the Reaction of Vibrationally Excited CH3F Molecules with F2
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The kinetics of reactions initiated via F2 photolysis in solid methane at 15 K was studied with IR spectroscopy.CH3F...HF complexes, formed in a cage reaction with a quantum yield of 0.55 +/- 0.10, are the main products of the photolysis at a host:guest matrix ratio MIR > 5.At MIR 100 the formation of CH2F2 is also detected.Its quantum yield grows linearly with F2 concentration in the MIR range 100-13.The formation of CH2F2 is suggested to be due to the reaction of the F2 molecule with a highly vibrationally excited primary product CH3F*, formed upon photolysis of the reactant clusters (F2*CH4*F2).
- Misochko, E. Ya.,Benderskii, V. A.,Goldschleger, A. U.
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- A Very Strong Methylation Agent: [Me2Cl][Al(OTeF5)4]
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A new chloronium-containing salt, [Me2Cl][Al(OTeF5)4], was synthesized on multigram scale by means of a simple one-pot procedure. The isolated product can be handled at room temperature and used as a strong electrophilic methylation agent. This is demonstrated by the methylation of the very weak bases P(CF3)3, PF3, MeI, and MeBr.
- H?mmerling, Sebastian,Thiele, Günther,Steinhauer, Simon,Beckers, Helmut,Müller, Carsten,Riedel, Sebastian
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supporting information
p. 9807 - 9810
(2019/06/24)
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- COMPOSITION INCLUDING FLUOROMETHANE AND METHOD FOR PRODUCING SAME
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An object of the present invention is to provide a composition containing fluoromethane having high purity. A method for producing fluoromethane, comprising: pyrolyzing in a gas phase a fluorine-containing methyl ether represented by Formula (1): wherein R1 and R2 are the same or different, and each represents an optionally substituted linear or branched monovalent aliphatic hydrocarbon group, an optionally substituted monovalent aromatic hydrocarbon group, an optionally substituted monovalent cyclic aliphatic hydrocarbon group, hydrogen, or halogen, in the presence of an alumina catalyst to thereby obtain a mixed gas containing fluoromethane and acid fluoride, wherein: the alumina catalyst contains chlorine in an amount of 1.0 wt % or less.
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Paragraph 0068-0070
(2018/06/04)
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- METHOD FOR PRODUCING METHANE FLUORIDE
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PROBLEM TO BE SOLVED: To provide a method for obtaining methane fluoride by reacting a raw material gas containing a methyl halide represented by the general formula CH3X (X represents a halogen atom other than a fluorine atom, hereinafter the same) and hydrogen fluoride in the presence of a catalyst in which a contact time of the raw material gas with a catalyst is shortened while maintaining the amount of production. SOLUTION: There is provided a method for producing methane fluoride by reacting a raw material gas containing a methyl halide represented by the general formula CH3X (X represents a halogen atom other than a fluorine atom) and hydrogen fluoride in the presence of a catalyst, wherein a contact time (W/F) of the raw material gas with a catalyst is more than 0.3 g sec/mL and less than 3 g sec/mL. SELECTED DRAWING: None COPYRIGHT: (C)2017,JPOandINPIT
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Paragraph 0034; 0035; 0036; 0038; 0040
(2017/10/05)
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- Method for preparing fluorinated compound CH2F-R (R is H or CF3) through difluoromethane pyrolysis
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The invention discloses a method for preparing a fluorinated compound CH2F-R (R is H or CF3) through difluoromethane pyrolysis. According the method, the fluorinated compound is obtained through a gas-phase reaction between difluoromethane and CH4, NH3, H2O or H under the circumstance that no catalyst exists. The following reaction conditions of the method are achieved: the reaction pressure is 0.1-1.5 MPa; the reaction temperature is 700-1000 DEG C; the mole ratio of difluoromethane to any one or more of CH4, NH3, H2O and H is 1:(0-40); and the residence time is 0.1-50 s. The method disclosed by the invention has the advantages that the raw material, namely difluoromethane, is easy to obtain; no catalyst needs to use; the operation and the control are easy; and the experimental repeatability is high.
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Paragraph 0046-0049
(2017/05/18)
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- MANUFACTURING METHOD OF METHANE FLUORIDE
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PROBLEM TO BE SOLVED: To provide a method for elongating life of a catalyst in a conventionally known method for manufacturing methane fluoride by thermal decomposition of fluorine-containing methyl ether in a presence of a catalyst. SOLUTION: There is provided a method for manufacturing methane fluoride by gas phase thermal decomposition of fluorine-containing methyl ether represented by the formula (1) in a presence of a catalyst for thermal decomposition in a presence of at least one kind of gas selected from hydrogen fluoride, chloride, hydrogen chloride and air. (1), where R1 and R2 are each independently a substituted/unsubstituted linear/branched monovalent aliphatic hydrocarbon group, monovalent aromatic hydrocarbon group or monovalent cyclic aliphatic hydrocarbon group, H or a halogen atom. SELECTED DRAWING: None COPYRIGHT: (C)2016,JPOandINPIT
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Paragraph 0055-0059
(2017/03/24)
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- METHOD FOR MANUFACTURING METHYL FLUORIDE
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An object of the present invention is to provide a method for producing methane fluoride that is useful, for example, as a dry etching gas, the method being more suitable for industrial production. To achieve this object, the present invention provides a method including reacting (A) dimethyl sulfate and (B) at least one fluorocompound in a liquid phase, the fluorocompound (B) being at least one compound selected from the group consisting of hydrogen fluoride and hydrofluoric acid salts, or a metal fluoride, wherein when the fluoride compound (B) includes hydrogen fluoride or a hydrofluoric acid salt, the reaction is carried out without a solvent or using a polar solvent as a solvent, and when the fluoride compound (B) is a metal fluoride, the reaction is carried out using water as a solvent.
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Paragraph 0053
(2016/07/05)
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- METHOD FOR MANUFACTURING METHYL FLUORIDE
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An object of the present invention is to provide a method for producing methane fluoride that is useful, for example, as a dry etching gas, the method being more suitable for industrial production. To achieve this object, the present invention provides a method including reacting (A) dimethyl sulfate and (B) at least one fluorocompound in a liquid phase, the fluorocompound (B) being at least one compound selected from the group consisting of hydrogen fluoride and hydrofluoric acid salts, or a metal fluoride, wherein when the fluoride compound (B) includes hydrogen fluoride or a hydrofluoric acid salt, the reaction is carried out without a solvent or using a polar solvent as a solvent, and when the fluoride compound (B) is a metal fluoride, the reaction is carried out using water as a solvent.
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Paragraph 0119; 0120
(2017/01/09)
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- METHOD FOR PRODUCING DRY ETCHING GAS
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Provided is a method for producing fluoromethane and 3,3,3-trifluoro-2-(trifluoromethyl)propanoyl fluoride ((CF3)2CHCOF), which are useful as dry etching gases etc., safely and inexpensively with high purity. According to the method in which 1,1,3,3,3-pentafluoro-2-trifluoromethylpropyl methyl ether is pyrolyzed in a gas phase in the presence of a catalyst, the desired fluoromethane and 3,3,3-trifluoro-2-(trifluoromethyl)propanoyl fluoride can be obtained with high selectivity and high conversion of the starting material by a simple process in which a pyrolysis reaction is performed in a gas phase using the inexpensive starting material.
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Paragraph 0049; 0050; 0060
(2015/11/18)
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- Method of manufacturing monofluoromethane
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PROBLEM TO BE SOLVED: To provide a convenient method for producing monofluoromethane, by which monofluoromethane is produced with a high yield, which is suitable for producing high-purity monofluoromethane usable as an etching agent or a cleaning agent etc., in a thin film process of a semiconductor industry, and which is conducted with a simple apparatus and an easy operation. SOLUTION: The method for producing high-purity monofluoromethane includes a step of making dimethyl sulfate and an alkali metal fluoride such as potassium fluoride react with each other in the presence of a solvent with polarity such as diglyme and sulfolane. COPYRIGHT: (C)2013,JPOandINPIT
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Paragraph 0034-0035; 0036; 0037; 0038
(2018/11/22)
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- Method for Producing Difluoroacetyl Chloride
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A production method of difluoroacetyl chloride according to the present invention includes a chlorination step of bringing a raw material containing at least either a 1-alkoxy-1,1,2,2-tetrafluoroethane or difluoroacetyl chloride into contact with calcium chloride at a reaction enabling temperature. A production method of 2,2-difluoroethyl alcohol according to the present invention includes a catalytic reduction step of causing catalytic reduction of the difluoroacetyl chloride obtained by the above production method. By these methods, the difluoroacetyl fluoride can be efficiently converted to the difluoroacetyl chloride and to the 2,2-difluoroethyl alcohol.
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Paragraph 0084
(2013/03/26)
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- Rhodium-carbon bond energies in Tp′Rh(CNneopentyl)(CH2X)H: Quantifying stabilization effects in M-C bonds
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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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- FLUORINE-CONTAINING COMPOUND PURIFICATION METHOD
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There is provided a fluorine-containing compound purification method for obtaining a high-purity fluorine-containing compound by efficiently separating and removing hydrogen chloride from a fluorine-containing compound that contains hydrogen chloride, i.e., from a crude fluorine-containing compound. The fluorine-containing compound purification method of the present invention comprises the following steps (1) and (2) in this order: step (1): a step of adding dimethyl ether to a crude fluorine-containing compound that contains a fluorine-containing compound and hydrogen chloride in a molar ratio (dimethyl ether (mol)/hydrogen chloride (mol)) of dimethyl ether to hydrogen chloride being 1.3 or more to prepare a mixture (1) of the crude fluorine-containing compound and dimethyl ether; andstep (2): a step of separating and removing a mixture (2) of hydrogen chloride and dimethyl ether from the mixture (1).
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Page/Page column 4-5
(2012/09/05)
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- METHOD FOR PRODUCING DIFLUOROACETIC ACID ESTER
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A production method of a difluoroacetic acid ester according to the present invention includes at least: a reaction step of obtaining a liquid by reaction of an alcohol represented by ROH with difluoroacetic acid fluoride (CHF2COF) in the presence of an amide compound of the following formula (1) or a sulfone compound of the following formula (2) as a hydrogen fluoride trapping agent; and a distillation step (A) of extracting a difluoroacetic acid ester represented by CHF2COOR by distillation of the reaction liquid obtained in the first step. In the present production method, there occurs no deterioration in the yield of the product due to the inherent generation of hydrogen fluoride as a by-product during the esterification reaction of difluoroacetic acid fluoride.
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Page/Page column 8-9
(2012/12/13)
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- Green synthesis of methyl trifluoropyruvate catalyzed by solid acids
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Solid acids - NiSO4/Al2O3, Fe2(SO4)3/Al2O3 and TiO2/SO42- - appeared to be effective catalysts for the acid catalyzed synthesis of met
- Lermontov, Sergey A.,Ushakova, Lyudmila L.,Kuryleva, Nina V.
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p. 332 - 334
(2008/12/22)
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- Competitive demethylation and substitution in N,N,N-trimethylanilinium fluorides
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Fluorination of aromatic compounds by nucleophilic displacement of trimethylanilinium salts by fluoride is a commonly used reaction for radiotracer synthesis. Though the liberated trimethylamine is thought to be an excellent leaving group for this type of SNAr reaction, scattered reports show that amine demethylation (reverse Menschutkin reaction) sometimes dominates over substitution, particularly when relatively electron rich fluoroarenes are the desired targets. Here we provide systematic experimental and theoretical studies of trimethylanilinium demethylation and substitution. Results from these studies highlight the limits of this leaving group in fluoroarene synthesis and have important ramifications for the design of nucleophilic fluorinating agents featuring ammonium cations.
- Sun, Haoran,DiMagno, Stephen G.
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p. 806 - 812
(2008/03/14)
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- FLUOROMETHANE PRODUCTION PROCESS AND PRODUCT
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Methyl chloride and hydrogen fluoride are reacted in a gas phase in the presence of a fluorination catalyst and the resulting mixture, containing fluoromethane and hydrogen chloride, is fed to a distillation column for separation and purification of the fluoromethane and hydrogen chloride as the overhead fraction. It is thus possible to efficiently produce high purity HFC-41 which is suitable for use as a semiconductor etching gas.
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Page/Page column 9
(2008/06/13)
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- Catalytic conversion of hydrofluoroalkanol to hydrofluoroalkene
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Methane is used as the selective dehydrating agent for the production of 2,3,3,3-tetrafluoro-1-propene (R1234yf) from 2,2,3,3,3-pentafluoro-1-propanol. Supported transition metal catalysts are prepared and used for this reaction with high activity. Almost 58% selectivity to R1234yf is obtained at an alcohol conversion level of 60% using unsupported Ni-mesh as the catalyst. Pd and Pt show almost similar level of conversion; however, the selectivity to the desired product is low. The activity of the metal catalyst was found to be a function of the type of support material, activated carbon showing better activity than alumina. Different important process parameters such as temperature, pressure, and contact time are studied to optimize the process. High pressure and temperature are deleterious to the rate of 1234yf formation; yet, the highest yield to 1234yf is obtained while performing a reaction at 494° C. with a contact time of 23 sec.
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Page/Page column 3-4
(2008/06/13)
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- Anhydrous flouride salts and reagents and methods for their production
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Anhydrous organic fluoride salts and reagents prepared by a method comprising the nucleophilic substitution of a fluorinated aromatic or fluorinated unsaturated organic compound with a salt having the formula: [QnM]x+Ax?in an inert polar, aprotic solvent; wherein M is an atom capable of supporting a formal positive charge, the n groups Q are independently varied organic moieties, n is an integer such that the [QnM] carries at least one formal positive charge, x is an integer defining the number of formal positive charge(s), +, carried by the [QnM], A? is an anionic nucleophile capable of substituting for F in the fluorinated compound and F represents fluorine or a radioisotope thereof.
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Page/Page column 3-5
(2008/06/13)
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- Anhydrous tetrabutylammonium fluoride
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Tetrabutylammonium fluoride (TBAF) is prepared at low temperature by nucleophilic aromatic substitution of hexafluorobenzene with tetrabutylammonium cyanide. Adventitious water is scavenged during this synthesis by the generated hexacyanobenzene, which readily adds water under basic conditions. Contrary to expectations, TBAF is stable to Hofmann elimination in polar aprotic solvents under anhydrous conditions. Added hydroxylic solvents are shown to catalyze the decomposition of TBAF and to catalyze proton exchange with DMSO. The synthetic utility of this salt is described briefly. Copyright
- Sun, Haoran,DiMagno, Stephen G.
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p. 2050 - 2051
(2007/10/03)
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- PROCESS FOR PURIFYING PENTAFLUOROETHANE, PROCESS FOR PRODUCING THE SAME, AND USE THEREOF
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ABSTRACT A process comprising bringing crude pentafluoroethane containing at least one compound selected from the group consisting of hydrofluorocarbons containing one carbon atom, hydrochlorofluorocarbons containing one carbon atom and hydrochlorocarbons containing one carbon atom, into contact with an adsorbent comprising a zeolite having an average pore size of 3 to 6 ? and a silica/aluminum ratio of 2.0 or less and/or a carbonaceous adsorbent having an average pore size of 3.5 to 6 ?, to reduce the content of the compound. The purified gas can be used as a low temperature refrigerant or an etching gas.
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- A new synthesis of trifluoromethanethiolates - Characterization and properties of tetramethylammonium, cesium and di(benzo-15-crown-5)cesium trifluoromethanethiolates
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[NMe4]SCF3, CsSCF3 and [(B-15-C-5)2Cs]SCF3 (B-15-C-5: benzo-15-crown-5) are formed from reactions of the corresponding fluorides, trimethyl(trifluoromethyl)silane, Me3SiCF3, and elemental sulfur in glyme or THF. All compounds are colorless to pale ochre solids decomposing significantly above ambient temperature. Excellent agreement between experimental and theoretical vibrational frequencies, calculated at the B3PW91 level of theory, impressively confirms the salt-like nature of [NMe4]SCF3. The properties of the title compounds as nucleophilic SCF3 transfer reagents were checked with a variety of organic, organometallic and inorganic compounds.
- Tyrra, Wieland,Naumann, Dieter,Hoge, Berthold,Yagupolskii, Yurii L.
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p. 101 - 107
(2007/10/03)
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- Characterization and reactivity of Pd/MgO and Pd/?3-Al2O3 catalysts in the selective hydrogenolysis of CCl2F2
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Al2O3 and MgO supported Pd catalysts with 6 wt % loading are prepared by the wet impregnation method. The catalysts are made into two parts; one of them is dried at 110 ?°C, and the other one is calcined at 500 ?°C. Conversion of CCl
- Aytam, Hari Padmasri,Akula, Venugopal,Janmanchi, Krishnamurthy,Rao Kamaraju, Seetha Rama,Rao Panja, Kanta,Gurram, Kishan,Niemantsverdriet
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p. 1024 - 1031
(2007/10/03)
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- Esterification of 1,2-dichloro-1,1,2-trifluoro-2-methoxyethane with AlFm(OH)3-m
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Porous AlFm(OH)3-m was prepared by heating AlF3·3H2O. Methyl chlorodifluoroacetate was synthesized in 77% yield by the reaction of 1,2-dichloro-1,1,2-trifluoro-2-methoxyethane with AlFm(OH)3-m/s
- Quan, Heng-Dao,Tamura, Masanori,Gao, Ren-Xiao,Sekiya, Akira
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p. 4111 - 4114
(2007/10/03)
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- An experimental and modelling study of ignition delays in shock-heated ethane-oxygen-argon mixtures inhibited by 2H-heptafluoropropane
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Ignition delay times have been measured behind reflected shock waves in ethane-oxygenargon mixtures at temperatures between 1150 and 1500 K and pre-ignition pressures between 10 and 14 atm. Delay times have been measured both by pressure rise and OH absorption at 307 nm. Kinetic modelling of the ignition delays has been made using the GRIMech 3.0 mechanism which with addition of several reactions involving HO2 radicals and an increase in the barrier for reaction between C2H5 and O2 can satisfactorily model delays over the studied equivalence ratios of φ= 1.7 to 0.68. Addition of 2H-heptafluoropropane up to 13 mol % (of ethane) had little inhibition effect on stoichiometric ethane-oxygen-argon mixtures but inhibited ignition in a mixture of φ= 1.5. A kinetic mechanism is presented to model the inhibition process. by Oldenbourg Wissenschaftsverlag, Muenchen.
- Ikeda, Emi,Mackie, John C.
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p. 997 - 1009
(2007/10/03)
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- The nucleophilic displacement (S(n)2) reaction F- + CH3Cl → CH3F + Cl- induced by resonant electron capture in gas phase clusters
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It is shown that the title nucleophilic displacement reaction can be observed in a crossed beam experiment where binary clusters composed of NF3 and CH3Cl interact with a monochromatized electron beam. The nucleophile, F- is generated within an energy region around 2 eV by resonant dissociative electron attachment (DA) from the NF3 component of the cluster and then undergoes an S(N)2 reaction with the 'substrate' molecule CH3Cl. While low energy electron impact to CH3Cl gives no measurable Cl- signal due to the extremely low DA cross section (-22 cm2), we observe copious amounts of Cl- ions from the mixed cluster ions carrying the DA resonance profile of F-/NF3 which are hence identified as products of the corresponding S(N)2 reaction.
- Langer, Judith,Matejcik, Stefan,Illenberger, Eugen
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p. 1001 - 1005
(2007/10/03)
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- Oxidative fluorination of S, Se and Te compounds
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The synthesis and mechanism of formation of cis- and trans-Ph2SF4 is described. Starting compounds are Ph2S or Ph2SF2 and the oxidizing agent is XeF2 in the presence of Et4NCl. Also described is the synthesis of related chalcogen(IV and VI) fluorides such as t-butylSF3, difluorodibenzothiophene, PhSeF3, Ph2SeF2, PhSF5, p-MeC6H4SF5, PhSeF5, and PhTeF5. The reactions of Ph2S(O)F2 with alcohols and with the H2O-HF-glass system are briefly described.
- Ou, Xiaobo,Janzen, Alexander F.
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p. 279 - 283
(2007/10/03)
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- Acid fluorides and 1,1-difluoroethyl methyl ethers as new organic sources of fluoride for antimony pentachloride-catalyzed halogen-exchange reactions
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1,1-Difluoroethyl methyl ethers such as the commercial veterinary anesthetic methoxyflurane (2,2-dichoro-1,1-difluoroethyl methyl ether, 6) decompose in the presence of a catalytic amount of antimony pentachloride. The rate of decomposition is dependent upon the number and position of halogen atoms in the ether: a high degree of halogenation at the methyl group or at the 2-position of the ethyl group makes the ether less prone to decomposition. The decomposition products are acid fluorides and halogenated methanes. The fate of the antimony pentachloride is conversion to a fluorochloroantimony species which can be used in situ to selectively fluorinate a polychlorinated substrate. Thus, 1,2,2,2-tetrachloro-1-fluoroethyl methyl ether (1) is converted cleanly to the anesthetic compound 2,2,2-trichloro-1,1-difluoroethyl methyl ether (2) using 6 as the fluoride source, exploiting the difference in stability of 2 and 6 to the pentavalent antimony species. It is also demonstrated that the acid fluorides obtained from decomposition of the 1,1-difluoroethyl methyl ethers are fluoride sources for halex reactions.
- Ramig, Keith,Kudzma, Linas V.,Lessor, Ralph A.,Rozov, Leonid A.
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- Internal excitation in the products of nucleophilic substitution from the dissociation of metastable ion complexes
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The relative kinetic energy distributions for the products of the dissociation of four metastable gasphase ion clusters have been analyzed by means of ion kinetic energy spectroscopy, and the results modeled using statistical phase space theory. The systems studied represent reaction intermediates in bimolecular nucleophilic substitutions (S(N)2). These studies build on previous investigations that demonstrated vibrational excitation in the products of the substitution reactions of halide ions with methyl halides. The present studies explore the effects of molecular structure, reaction exothermicity, and nucleophile and leaving group variation. The experimental kinetic energy distributions are compared with theoretical distributions calculated for statistical partitioning of energy among internal modes and relative kinetic energy of the products. In each reaction, the calculated distributions agree with the experimental distributions only if a significant fraction of the energy released in the exothermic reactions is assumed to be unavailable for randomization in the dissociation. The results suggest that the products of these S(N)2 reactions are internally excited.
- Graul, Susan T.,Carpenter, Catherine J.,Bushnell, John E.,Van Koppen, Petra A. M.,Bowers, Michael T.
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p. 6785 - 6796
(2007/10/03)
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- New method of preparation of fluoro compounds via utilisation of ammonium and phosphonium perfluorocyclobutane ylides as fluorination reagents
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Ammonium- and phosphoniumperfluorocyclobutane ylides (7-11), easily prepared from perfluorocyclobutene (1) and tertiary amines (2-4) or phosphines (5,6), smoothly react with primary or secondary alcohols (12-18) and carboxylic acids (19, 20) with formation of alkyl fluorides (21-26) or acyl fluorides (27, 28), respectively. A mechanism for the reaction is proposed.
- Pasenok, Sergej V.,De Roos, Marijn E.,Appel, Wolfgang K.
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p. 2977 - 2982
(2007/10/03)
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- Gas-Phase Nucleophilic Displacement Reactions
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Displacement reactions of each of a variety of anionic nucleophiles reacting with each of a variety of neutrals have been studied by pulsed ion cyclotron resonance (ICR) spectroscopy.Rate constants for these reactions are interpreted in terms of a three-step reaction sequence.RRKM calculations are used to obtain information about the energy of transition states.The origin of the barrier to reaction in solution is discussed.
- Olmstead, William N.,Brauman, John I.
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p. 1653 - 1662
(2007/10/03)
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- Temperature Dependence and Product Distribution for the Reaction of CF3O Radicals with Methane
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The rate coefficient for the reaction (1) CF3O + CH4 --> CF3OH + CH3 has been determined using a combined laser photolysis/LIF technique.From measurements in the temperature range 235-401 K the Arrhenius expression k1 = (3.3 +/- 0.8)E-12 exp. cm3/s, corresponding to k1 = 2.5E-14 cm3/s at 298 K is obtained.The products of reaction (1) have been identified by independent experiments using a steady-state/FTIR technique.It is concluded that the main primary product of reaction (1) is CF3OH which decomposes under our experimental conditions to yield CF2O and HF.An upper limit of the decomposition rate coefficient for (7) CF3OH --> CF2O + HF at 298 K of k7 -1 is determined. - Keywords: CF3O radicals / Laser photolysis / LIF technique / H abstraction from CH4 / Decomposition of CF3OH
- Bednarek, G.,Kohlmann, J. P.,Saathoff, H.,Zellner, R.
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- FLUORINATION OF METHANE AND ITS FLUORINE DERIVATIVES BY COBALT TRIFLUORIDE
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Fluorination of methane is studied with the aim of using difluoromethane and trifluoromethane as promising ozone-safe refrigerants.Principal kinetic features of fluorination of methane, difluoromethane, and trifluoromethane is gas phase are determined.Activation energies and preexponential factors of the rate constants of the main reactions are presented.The process studied is shown to be promising for industrial production of fluoromethanes.
- Asovich, V. S.,Kornilov, V. V.,Kostyaev, R. A.,Maksimov, V. N.
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- Electrophilic fluorination of methane with "F+" equivalent N2F+ and NF4+ salts1
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The electrophilic fluorination of methane with "F+" equivalent N2F+ and NF4+ salts was studied by experiment and theory. Reaction of excess methane with NF4+SbF6- in pyridinium polyhydrogen fluoride solution gave exclusively methyl fluoride. The reaction of N2F+AsF6- and NF4+AsF6- with methane (with 1:2 to 4:1 mole ratio, respectively) in HF solution gave methyl fluoride in 63-92% relative yield with 26-6% methylene fluoride and 2-11% fluoroform with no carbon tetrafluoride formed. In a theoretical study of the CH4 + F+ model reaction stationary points on the potential energy surface were calculated at the QCISD/6-31G*//QCISD/6-31G* + ZPE level. The mechanistic consequences of these reactions are discussed.
- Olah, George A.,Hartz, Nikolai,Rasul, Golam,Wang, Qi,Prakash, G. K. Surya,Casanova, Joseph,Christe, Karl O.
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p. 5671 - 5673
(2007/10/02)
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- Syntheses and Reactions of Fluoroorganic Acyclic Thiocarbenium Ions
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Arsenic pentafluoride oxidizes (F3CS)4C (1) but not (F3CS)2C=C(SCF3)2 (2) to yield the stable salt (F3CS)3C(+)AsF6(-) (3).It reacts with halide ions to form (F3CS)3CX (3a-c, X = F, Cl, Br).Iodide is oxidized to iodine with formation of (F3CS)3CC(SCF3)3 (4) which reacts with nitrogen dioxide to give (F3CS)3CNO2 (3e). - (F3CS)3C(+)AsF6(-) (3) removes from (5a) a ring-bound fluorine atom to afford (F3CS)3CF and (5).When (F3CS)3CCl (3b) is treated with AsF5, 3 and (+)AsF6(-) (6) are formed in a 2:1 molar ratio.The latter reacts with F(-) or Cl(-) to give (F3CS)2CClX (6a,b; X = F, Cl).AsF5 is capable of abstracting a fluoride ion from (F3CS)3-nClnCF only if n = 0 or 1.For n = 2 no similar reaction takes place, but with AlCl3 in BCl3 halogen exchange to F3CSCCl3 (7b) is observed. - Alkylation of (F3CS)2C=S (8) with H3CF/AsF5 yields (+)AsF6(-) (9), which adds a fluoride ion to give (F3CS)2(H3CS)CF (9a).The molecular structures of (F3CS)2C=C(SCF3)2 (2) and (F3CS)3CC(SCF3)3 (4) have been determined by X-ray diffraction methods. - Key Words: (Trifluoromethylthio)carbon / Carbenium ions / One-electron oxidation / Superacidic systems
- Boese, Roland,Haas, Alois,Krueger, Carl,Moeller, Guido,Waterfeld, Alfred
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p. 597 - 604
(2007/10/02)
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- Tetrafluorophosphite, PF4-, anion
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N(CH3)4+PF4-, the first example of a PF4- salt, has been prepared from N(CH3)4F and PF3 using either CH3CN, CHF3, or excess PF3 as a solvent. The salt is a white, crystalline solid which is thermally stable up to 150 °C where it decomposes to N(CH3)3, CH3F, and PF3. The structure of the PF4- anion was studied by variable temperature 31P and 19F NMR spectroscopy, infrared and Raman spectroscopy, SCF, MP2, local and nonlocal density functional calculations, a normal coordinate analysis, and single-crystal X-ray diffraction. The anion possesses a pseudo trigonal bipyramidal structure with two longer axial bonds and an equatorial plane containing two shorter equatorial bonds and a sterically active free valence electron pair. In solution, it undergoes an intramolecular exchange process by the way of a Berry pseudorotation mechanism. The vibrational frequencies observed for PF4- in solid N(CH3)4PF4 are in excellent agreement with those calculated for free gaseous PF4-. The X-ray diffraction study tetragonal, space group P4?21m, a = 8.465(3) A?, c = 5.674(2) A?, Z = 2, R = 0.0723 for 268 observed [F ≥ σ(F)] reflections suffers from a 3-fold disorder with unequal occupancy factors for the equatorial fluorine atoms of PF4- but confirms its pseudo trigonal bipyramidal structure and the axial P-F bond length calculated for the free ion.
- Christe, Karl O.,Dixon, David A.,Mercier, Hélène P. A.,Sanders, Jeremy C. P.,Schrobilgen, Gary J.,Wilson, William W.
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p. 2850 - 2858
(2007/10/02)
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- Energy Disposal in Gas-phase Nucleophilic Displacement Reactions
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The partitioning of reaction exothermicity into relative translational energy of the products of gas-phase SN2 (F- + CH3Cl) and nucleophilic aromatic substitution F- + C6H5Cl) reactions has been investigated using kinetic energy release Fourier transform ion cyclotron resonance spectroscopy.The chloride product ion is observed to be highly translationally excited for the Sn2 reaction, indicating a cold internal energy distribution for the products.For the chlorobenzene reaction the products are not generated with large translational energies.The results are compa red with a statistical model.Ion-intensity profiles for the CH3Cl reaction deviate significantly from the statistical model whereas the chlorobenzene results are consistent with this model.The kinetic energy release for the CH3Cl reaction is compared with energy-diposal results for the photodissociation and dissociative electron-attachment processes of halomethanes.In all three cases a node in the molecular orbital between the carbon atom and the departing halogen results in a repulsive energy release.Ion-retention curves for the nucleophilic aromatic substitution reaction are consistent with the existence of a long-lived ion-dipole complex on the exit channel for this reaction.
- VanOrden, Steven L.,Pope, R. Marshall,Buckner, Steven W.
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p. 1003 - 1007
(2007/10/02)
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- Fourier-transform Infrared Product Study of the Reaction of CH3O2 + HO2 over the Pressure Range 15-700 Torr at 295 K
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Fourier-transform infrared spectroscopy was used to establish methyl hydroperoxide as the dominant product of the gas-phase reaction of methylperoxy radicals with hydroperoxy radicals.Over the pressure range 15-700 torr of either air or oxygen, 92 +/- 5percent of the reaction of CH3O2 with HO2 proceeds via channel (1a): CH3O2 + HO2 -> CH3OOH + O2 (1a).Quoted errors represent 2?.This result is discussed with respect to previous kinetic and mechanistic studies of peroxy radicals and computer models of atmospheric chemistry.
- Wallington, Timothy J.
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p. 2379 - 2382
(2007/10/02)
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- Gas-phase SN2 and E2 reactions of alkyl halides
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Rate coefficients have been measured for the gas-phase reactions of methyl, ethyl, n-propyl, isopropyl, tert-butyl, and neopentyl chlorides and bromides with the following set of nucleophiles, listed in order of decreasing basicity: HO-, CH3O-, F-, HO- (H2O), CF3CH2O-, H2NS-, C2F5CH2O-, HS-, and Cl-. For methyl chloride the reaction efficiency first falls significantly below unity with HO- (H2O) as the nucleophile and for methyl bromide with HS- as the nucleophile; in both cases the overall reaction exothermicity is about 30 kcal mol-1. Earlier conclusions that these halides react slowly with stronger bases are shown to be in error. In the region where the rates are slow oxygen anions react with the alkyl chlorides and bromides by elimination while sulfur anions of the same basicity react by substitution. This difference is due to a slowing down of elimination with the sulfur bases; sulfur anions show no increased nucleophilicity as compared to oxy anions of the same basicity. Rate coefficients have also been measured for reaction of methyl fluoride with HO- and CH3O- and ethylene oxide with HO-, CH3O-, and F-. All of these rates are slow but measurable; combining the results of these experiments with those of the alkyl chlorides and bromides suggests that the gas-phase barrier to the symmetrical SN2 reaction of F- with methyl fluoride is lower than previous estimates. We have also measured rates for reaction of allyl chloride with F-, H2NS-, and HS-, chloromethyl ether with H2NS- and HS-, chloroacetonitrile with F-, H2NS-, HS-, and 37Cl-, bromoacetonitrile with Cl- and 81Br-, and α-chloroacetone with H2NS-, HS-, and 37Cl-. Our results also imply that the gas-phase SN2 barrier for Br- reacting with methyl bromide is nearly equal to the ion-dipole attraction energy of the reactants, in agreement with previous estimates.
- DePuy, Charles H.,Gronert, Scott,Mullin, Amy,Bierbaum, Veronica M.
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p. 8650 - 8655
(2007/10/02)
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- A New HCN Production from CCl2F2 (CFC12) and Ammonia over NiTiO3, Ni metal, and Pt/C Catalysts
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NiTiO3, Ni metal, and Pt/C are effective catalysts for the formation of HCN from CFC12 and NH3 at 673-823 K: 86.2percent yield is attained at 723 K over Ni metal.
- Takita, Yusaku,Ishihara, Tatsumi,Hashida, Masayo
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p. 1247 - 1248
(2007/10/02)
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- UNUSUAL REACTION CHEMISTRY IN THERMAL DECOMPOSITION OF ALKALI METAL 2-ALKOXY-2,3,3,3-TETRAFLUOROPROPIONATE SALTS
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Pyrolyses of several salts ROCF(CF3)CO2(-)M(+) (R=Me, Et, CF3CH2; M=Na, K, Cs) have been studied.The reaction chemistry shows highly unusual dependence on the nature of the alkoxy substituent and the metal cation.Product distribution are described along with some proposed mechanisms.
- Pellerite, Mark J.
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- Reactions of dimethoxycarbene and fluoromethoxycarbene with hydroxyl compounds. Absolute rate constants and the heat of formation of dimethoxycarbene
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Dimethoxycarbene [(MeO)2C] and fluoromethoxycarbene (FCOMe) were photochemically generated from the appropriate diazirines (2a and 2b) and characterized by UV and IR spectroscopy in cold matrices and by UV in solution at 20-25°C. Laser flash photolytic studies determined rate constants for the reactions of the carbenes with ethanol, methanol, chloroethanol, fluoroethanol, trifluoroethanol, hexafluoroisopropyl alcohol, and acetic acid. The reactivity of (MeO)2C with the alcohols spanned 4 orders of magnitude, with kψ for carbene decay in 1 M ROH/CH3CN ranging from 3.2 X 104 S-1 (ethanol) to 6.7 X 108 S-1 (hexafluoroisopropyl alcohol). A Bronsted correlation (α = 0.66) was obtained between log kψ for the decay of (MeO)2C in 1 M ROH/CH3CN and the pK(a) of ROH (in water). FCOMe was much less reactive toward ROH than (MeO)2C; only with hexafluoroisopropyl alcohol (kψ ~9 X 103 s-1 for carbene decay in 1 M ROH/CH3CN) could quenching be observed. Products of some of the carbene/alcohol reactions were characterized. A photoacoustic calorimetry study of the (MeO)2/MeOH reaction afforded ΔH(f) ~ -61 kcal/mol for (MeO)2C;ΔH(f) for FCOMe was estimated at ~ -53 to -56 kcal/mol. The mechanism(s) of the carbene/O-H insertion reactions are discussed. The results of ab initio and semiempirical molecular orbital calculations on FCOMe are presented.
- Du,Fan,Goodman,Kesselmayer,Krogh-Jespersen,LaVilla,Moss,Shen,Sheridan
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p. 1920 - 1926
(2007/10/02)
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