- Threshold effects in electron transfer to oriented molecules
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The effects of molecular orientation on electron transfer are explored in collisions between haloalkane molecules oriented in molecular beams and K atoms which have sufficient energy to allow the charged products to separate. For several molecules studied (CF3Br, CF3Cl, and CH3Br) attack at the "heads" end of the molecule (the end with the most weakly bound atom) always produces more K+ ions. The effect of orientation is most dramatic at energies near threshold (≈5 eV) and disappears at energies of ≈20 eV, showing that steric requirements are energy dependent. Heads orientation has a lower energy threshold than tails orientation so there is a limited energy region where reaction occurs only in the heads orientation. For CF3Br, the thresholds are 3.4 and 4.0 eV, corresponding to energies required for formation of CF3Br- and CF3 + Br-, respectively. For energies between 3.4 and 4.0 eV, reaction occurs only for attack at the Br end to form only two species, suggesting that the electron is preferentially transferred to the Br end of the molecule.
- Xing, Guoqiang,Kasai, Toshio,Brooks, Philip R.
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Read Online
- Gas-phase photodissociation of CF3C(O)Cl between 193 and 280 nm
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Product yields were measured in the 296 K photolysis of CF3C(O)Cl at 193, 248, 254, and 280 nm. Br2 was used as a radical scavenger to convert the primary CF3 and CF3CO radical photofragments into stable bromides, CF3Br and CF3C(O)Br, which were quantified along with CO and CF2O using infrared absorption. The stabilized CF3CO radical yield increased with increasing photolysis wavelength from 3Cl quantum yield was determined to be 0.001 at all wavelengths.
- McGillen, Max R.,Burkholder, James B.
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p. 189 - 194
(2015/10/12)
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- Me3SiCF3/AgF/Cu - A new reagents combination for selective trifluoromethylation of various organic halides by trifluoromethylcopper, CuCF3
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An alternative copper halide-free route to obtain highly reactive trifluoromethylcopper species has been developed via the reaction of silver fluoride and trimethyl(trifluoromethyl)silane followed by a redox transmetallation with elemental copper. The composition of the reactive intermediate was investigated by means of UV/Vis/NIR, ESR, 19F NMR spectroscopy and ESI mass spectrometry. "Trifluoromethylcopper" prepared by the oxidative transmetallation route exhibits excellent reactivity and selectivity in substitutions of iodine or bromine bond to aromatic or heterocyclic compounds for trifluoromethyl groups without any additional catalyst.
- Kremlev, Mikhail M.,Mushta, Aleksej I.,Tyrra, Wieland,Yagupolskii, Yurii L.,Naumann, Dieter,M?ller, Angela
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body text
p. 67 - 71
(2012/03/10)
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- The nascent OH detection in photodissociation of 2-(bromomethyl)hexafluoro- 2-propanol at 193 nm: Laser-induced fluorescence study
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Photodissociation of 2-(bromomethyl)hexafluoro-2-propanol (BMHFP) and 3-bromo-1-propanol (BP), involving σC-BrnBr transition at 193 nm, has been investigated by measuring laser-induced fluorescence spectra of the expected OH product. The OH channel is a minor dissociation pathway with a quantum yield of 0.17 ± 0.05 in BMHFP, whereas it was not observed in BP. Partitioning of the available energy into translation, rotation, and vibration of the photoproducts has been measured by state selective detection of the nascent OH product in BMHFP. OH is produced mostly in the ground vibrational level (v″ = 0), with a rotational distribution being characterized by a temperature of 465 ± 25 K. But, a significant fraction of the available energy of 30.2 kcal mol-1 is partitioned into translation of OH (14.6 kcal mol-1). The OH(v″ = 0, J″) populations in the spin-orbit states as well as in the Λ-doublet states are statistical. A plausible mechanism of OH formation on excitation of BMHFP at 193 nm is suggested, with the primary reaction channel being elimination of Br atom by direct C-Br bond dissociation from a repulsive surface. The Br radical is detected using (2 + 1) resonance-enhanced multiphoton ionization (REMPI) at ～234 nm. It is produced in both the ground (2P3/2) and the excited (2P1/2) spin-orbit states with the relative quantum yield of the latter to be 0.36. The co-fragment of Br undergoes secondary C-O bond dissociation to produce OH and F3C-C(CH 2)-CF3, with the reaction having a barrier located in the exit channel. In this two-step three-body dissociation process, a major fraction of the available energy is released into translation (〈fT〉 ～ 0.75), resulting from an impulsive C-Br bond dissociation in the primary step and presence of an exit barrier in the secondary process. Experimental results combined with theoretical calculations provide a clear picture of the dynamics of OH formation from BMHFP at 193 nm. In addition, the energetics of another channel, competing with OH, have been calculated from the primary product F3C-C(CH2)(OH)-CF3. In contrast to BMHFP, the OH product could not be observed from the photolysis of 3-bromo-1-propanol (another saturated halogenated propanol) at 193 nm under the detection limit of the present experimental condition, although it has a higher absorption cross-section at 193 nm.
- Indulkar, Yogesh N.,Upadhyaya, Hari P.,Kumar, Awadhesh,Waghmode, Suresh B.,Naik, Prakash D.
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experimental part
p. 210 - 219
(2012/07/14)
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- Conversion of CHF3 to CH2=CF2 via reaction with CH4 and CaBr2
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Reaction of CHF3 and CH4 over CaBr2 was investigated at 400-900°C as a potential route for transforming the highly potent greenhouse gas, CHF3, into the valuable product CH 2=CF2. The homogeneous reaction of CHF3 with CH4 was also studied to assist in understanding the chemistries involved. Compared to the gas phase reaction, the addition of CaBr2 as a reactant increases the conversion of CHF3 and CH4 significantly at low temperatures while to a lesser extent at higher temperatures. In the absence of CaBr2, besides the target product, CH2=CF2, a large amount of C2F4 forms. On addition of CaBr2, the rate of formation of C 2F4 drops dramatically to near zero, while the rate of formation of CH2=CF2 increases considerably at temperatures below 880°C. Experimental and theoretical studies suggest that CHF3 strongly interacts with CaBr2, resulting in the fluorination of CaBr2 to CaF2, the release of active Br species results in the selective formation of CBrF3. The subsequent reactions involving Br, methane, and CBrF3 play a major role in the observed enhanced yield of CH2=CF2.
- Han, Wenfeng,Yu, Hai,Kennedy, Eric M.,Mackie, John C.,Dlugogorski, Bogdan Z.
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p. 5795 - 5799
(2008/12/22)
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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 4
(2008/06/13)
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- Reactions of H3O+ and H2O+ with several fully halogenated bromomethanes
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The bimolecular rate coefficients and ion products for the reactions of H3O+ and H2O+ with the bromine-containing molecules CF3Br, CF2Br2, CF2BrCl, CFBr3, CFBr2Cl, and CBrCl3 at 300 K are reported. With the exception of the reactions of H3O+ with CF3Br and CF2BrCl, the rate coefficients are near the collisional values (k ≈ 10-9 cm3 molecule-1 s-1). The most efficient exit pathway for the majority of the H3O+ reactions is the formation of a trihalomethyl cation, together with water and a hydrogen halide as the neutral products. In each case, more than one trihalomethyl cation can be formed. The branching ratios are largest for the products resulting from the breaking of a C-F bond. This is attributed to the high bond strength of HF relative to HCl and HBr. Similarly for CBrCl3, the major product cation is CCl2Br+. The H2O+ reactions are found to proceed predominantly via charge transfer. For the reaction of H2O+ with CF3Br there is clear evidence for intimate reaction pathways in which bonds are broken and formed.
- Thomas,Kennedy,Mayhew,Watts
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p. 8489 - 8495
(2007/10/03)
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- Perfluoroalkyl hypobromites: Synthesis and reactivity with some fluoroalkenes
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The first perfluoroalkyl hypobromites have been prepared by the reaction of bromine(I) fluorosulfate with perfluorinated tertiary alkoxides of general formula RfC(CF3)2ONa where Rf=CF3 or CF3CF2. These hypobromites are of lower thermal stability but they behave similarly to analogous hypochlorites and decompose rapidly above -20 °C to give CF3C(O) CF3 and either CF3Br or CF3CF2Br. New polyfluoroethers generated from the reaction of perfluoroalkyl hypobromites with fluoroalkenes have been characterized by 19F and 1H NMR spectroscopy, IR spectroscopy and MS.
- Anderson, John D.O.,DesMarteau, Darryl D.
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p. 147 - 152
(2007/10/03)
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- Atmospheric Chemistry of CF2BrH: Kinetics and Mechanism of Reaction with F and Cl Atoms and Fate of CF2BrO Radicals
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A pulse radiolysis technique was used to investigate the kinetics and products of the reaction of CF2BrH with fluorine atoms at 296 K.This reaction forms an adduct which is in dynamic equilibrium with CF2BrH and fluorine atoms.The UV absorption spectrum of the adduct was measured relative to the UV spectrum of the CH3O2 radical over the range 230-380 nm.At 280 nm, an absorption cross section of (1.3 +/- 0.3)E-17 cm2 molecule-1 was determined.From the absorption at 280 nm the equilibrium constant K5 = /() was measured to be (1.59 +/- 0.13)E-17 cm3 molecule-1.In 1 atm of SF6, the forward rate constant k5 = (1.4 +/- 0.5)E-11 cm3 molecule-1 s-1 and the backward rate constant k-5 = (8.8 +/- 3.0)E5 s-1 were determined by monitoring the rate of formation and loss of the adduct.As part of the present work a relative rate technique was used to measure k(Cl + CF2BrH) = (5.8 +/- 1.0)E-15 cm3 molecule-1 s-1 at 296 K and 700 Torr of N2.The fate of the oxy radical, CF2BrO, in the atmosphere is bromine atom elimination and formation of COF2.
- Bilde, Merete,Sehested, Jens,Mogelberg, Trine E.,Wallington, Timothy J.,Nielsen, Ole J.
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p. 7050 - 7059
(2007/10/03)
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- Facile conversion of perfluoroacyl fluorides into other acyl halides
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Nine perfluoroacyl fluorides underwent halogen exchange when treated with anhydrous lithium halides to give acyl chlorides, bromides and iodides in high yields. The temperature dependence of this reaction is described. In the reaction with perfluorodiacyl fluoride, the diacyl halides possessing different acyl halide-groups were also produced. Of the alkaline metal salts used halogen exchange was successful only with lithium salts because of the interaction between lithium and fluorine.
- Fukaya, Haruhiko,Matsumoto, Tomonori,Hayashi, Eiji,Hayakawa, Yoshio,Abe, Takashi
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p. 915 - 920
(2007/10/03)
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- Gas-phase reactions of oxide and superoxide anions with CF4, CF3Cl, CF3Br, CF3I, and C2F4 at 298 and 500 K
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Rate constants and product branching fractions have been measured for the gas-phase reactions of oxide (O-) and superoxide (O2-) anions with the halocarbons CF4, CF3Cl, CF3Br, CF3I, and C2F4 using a variable temperature-selected ion flow tube (VT-SIFT) instrument operated at 298 and 500 K.The reactions of O- with CF3X (X = Cl, Br, I) are fast and produce F-, XF-, and XO- for all X.For CF3Cl and CF3Br, X- is also formed.For CF3I, CF3- and IOF- are minor products.O- reacts rapidly with C2F4 producing F- as the major ionic product, along with contributions from reactive detachment and minor formation of FCO-, CF3-, and C2F3O-.The reaction of O2- with CF3Cl is slow, and both clustering and X- formation were observed.For CF3Br and CF3I, the reactions with O2- are fast, and nondissociative charge transfer was observed in addition to X- formation.O2- reacts rapidly with C2F4 by reactive detachment, in addition to producing F- as the major ionic product with smaller amounts of F2-, FCO-, FCO2-, CF3O-, and C2F4O-.O- and O2- were both found to be unreactive with CF4 at 298 and 500 K.The efficiencies of the reactions of both O- and O2- with CF3X are greater for the heavier halides at both 298 and 500 K.The rate constants for the reactions of O2- with CF3X appear to correlate both with the rates of thermal electron attachment to CF3X and with the electron affinities of CF3X, indicating that the O2- + CF3X reaction mechanism may involve initial electron transfer followed by dissociation.Thus the negative electron affinity of CF3Cl may explain the very slow rate for reaction with O2- despite the available exothermic pathways.
- Morris, Robert A.
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p. 2372 - 2381
(2007/10/02)
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- Chemistry of H2O+ with C2F4, C2F6, and CF3X (X = F, Cl, Br, I)
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The reactions of H2O+ with CF4, C2F6, C2F4, CF3Cl, CF3Br, and CF3I have been studied at 300 and 499 K.The measurements were conducted using a variable-temperature-selected ion flow tube apparatus.H2O+ reacts via charge transfer with C2F4 with rate constants equal to 1.4 x 10-9 and 1.5 x 10-9 cm3 s-1 at 300 and 499 K, respectively.The reactions with CF3X (X = Cl, Br, I) all proceed at the collision rate at 300 and 499 K within experimental uncertainty.The rate constants are in the range 1.6 x 10-9 - 2.1 x 10-9 cm3 s-1.The reactions of H2O+ with CF3X produce CF3+ and CF2X+ for X = Cl, Br, I, CF2OH+ for X = Cl, Br, and CF3X+ for X = Br, I.The reaction with CF3Cl also forms the ionic product CF3OH2+.No reaction was observed between H2O+ and the reactant neutrals CF4 and C2F6; the rate constants are less than 5 x 10-12 cm3 s-1 at 300 and 499 K.Upper limits to the heats of formation of CF2Cl+, CF2Br+, and CF2I+ have been derived from the data and are -1, respectively.
- Morris, Robert A.,Viggiano, A. A.,Doren, Jane M. Van,Paulson, John F.
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p. 3051 - 3054
(2007/10/02)
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- Kinetics of the Reactions of Halogenated Methyl Radicals with Molecular Bromine
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The kinetics of seven reactions of halogenated methyl radicals (CH2Cl, CHCl2, CFCl2, CF2Cl, CF3, CH2Br, and CH2I) with molecular bromine were studied by using a heatable tubular reactor coupled to a photoionization mass spectrometer.Rate constants were measured as a function of temperature, typically between 296 and 532 K.Arrhenius activation energies were found to be small negative values (typically -2 kJ mol-1) for all reactions studied with the exception of that of the CF3 + Br2 reaction (whose activation energy is positive, but which could not determined accurately).The pattern of reactivity among 11 reactions of substituted methyl radicals with Br2 (which includes the 7 reactions studied here and 4 C(H)x(CH3)3-x + Br2 reactions (x = 0-3) studied earlier) has been accounted for by the inductive effect of the substituent atoms or groups.The sum of the Pauling electronegativities of these substituents provides a useful measure of their total inductive effect on the reaction rate constant.
- Timonen, R. S.,Seetula, J. A.,Niiranen, J.,Gutman, D.
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p. 4009 - 4014
(2007/10/02)
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- Diphenyl(trifluoromethyl)bismuth and phenylbis(trifluoromethyl)bismuth - new organoperfluoroalkyl derivatives of tervalent bismuth
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Diphenyl(trifluoromethyl)bismuth and phenylbis(trifluoromethyl)bismuth have been synthesized from Cd(CF3)2*2CH3CN and the corresponding phenylbismuth halides.The reactions of the new compounds are similar to those of tris(perfluoroorgano)bismuth compounds
- Pasenok, Sergej,Naumann, Dieter,Tyrra, Wieland
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p. C47 - C49
(2007/10/02)
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- TRIFLUORMETHYLIERUNGSREAKTIONEN VON Te(CF3)2 MIT HALOGENBENZOLEN UND METHYLBENZOLEN
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Substituent effects on yields and regioselectivity of photochemical and thermal trifluoromethylation reactions of Te(CF3)2 with halogen benzenes and methyl benzenes are investigated under comparable conditions.All reactions lead to trifluoromethylated products.The yields of the thermal are always higher than those of the corresponding photochemical reactions.The reactivity of the halobenzenes increases in the series C6H5-F a sidereaction, but H-substitution is the primary reaction pathway.During the reactions with iodobenzene tellurium containing compounds are also formed.The reactions with methyl benzenes show an increase in reactivity in the series hexamethylbenzene mesitylene toluene p-xylene.In all cases only ring substituted products are detected.Reactions with toluene and p-xylene yield tellurium containing compounds as well as addition products.The 19F-n.m.r spectra of the products are given.
- Naumann, Dieter,Kischkewitz, Jurgen
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p. 283 - 299
(2007/10/02)
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- ESR and Optical Evidence on Formation of the Cl(1-)...CCl3(1+) Ion Pair in 3-Methylpentane Matrices ψ-Irradiated at 77 K
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The well-known absorption band at 470 nm in CCl4-alkane systems is investigated.The results obtained are as follows: (1) the absorption band due to the radical cation of 5-methyldecane (5MD(1+)) in 5MD-CCl4-3MP systems converts into the 470-nm band. (2) In the conversation, the positive charge of the 5MD(1+) reacts with the unpaired electron of CCl3. radical. (3) CBrCl3 and CCl3F in 3MP glasses produce the absorption bands at 480 nm and 438 nm, respectively, and the nature of these bands is the same with that of the 470-nm band in the all points examined.Results 1 and 2 lead to the formation of CCl(3+) cations.We also obtain evidence on the formation of CCl3(1+) cations from CBrCl3 and CCl2F(1+) cations from CCl3F.It is evident that the band shift observed in the case of CBrCl3 is not attributable to the free ions CCl3(1+) nor to the solvent-separated ion pairs Br(1-)/solvent/CCl3(1+) but the formation of the charge-transfer contact ion pairs Br(1-)...CCl3(1+).Therefore, it is concluded that CCl4 and CCl3F in 3MP produce Cl(1-)...CCl3(1+) and Cl(1-)...CCl2F(1+), respectively.We also obtained the results that CBrF3, CClF3, and CCl2F2 in 3MP glasses yield the corresponding radical anions with absorption bands at 314, 300, and 314 nm, respectively, and that these radical anions are neutralized with the migrating positive charges of the 5MD(1+) formed.
- Truszkowski, Stanislaw,Ichikawa, Takahisa
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p. 4522 - 4526
(2007/10/02)
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- Process for the preparation of perfluoroalkyl ketones
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A process for the preparation of a perfluoroalkyl ketone. A perfluoroalkyl halide, zinc and an ester are brought into contact with one another. Preferably a polar aprotic solvent and/or a pyridine is also present.
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- Synthesis and characterization of (trifluoromethyl)gold complexes
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The synthesis of (CF3)AuL (L = PMe3, PEt3, PPh3) from LAuCl and Cd(CF3)2·DME is described. These linear gold(I) compounds readily add excess halogen to form the predominantly trans square-planar gold(III) dihalides (CF3)AuX2(L) (X = Br, I). The use of stoichiometric (or less) halogen leads to a significant quantity of (CF3)2AuX(L) (L = PMe3, PEt3) which is shown to arise from trifluoromethyl/halogen ligand exchange between (CF3)AuL and (CF3)AuX2(L). No evidence for ligand exchange is found when L = PPh3. (CF3)2AuI(L) (L = PMe3, PEt3) may also be prepared in 80% yield from the oxidative addition of trifluoromethyl iodide to (CF3)AuL; experiments with the radical scavenger galvinoxyl suggest a radical chain mechanism for this CF3I addition. Close examination of the 1H and 19F NMR spectra for the new square-planar complexes reveals that downfield shifts occur for both nuclei when a cis halide is changed from Br to I; a trans halide causes an upfield shift upon this substitution. The cadmium reagent is, in general, ineffective for the preparation of Au(III) complexes since reduction to (CF3)AuL usually occurs. However, treatment of (CF3)2AuI(PMe3) with Cd(CF3)2·DME in the presence of excess CF3I leads to the high-yield synthesis of the tris(trifluoromethyl) species (CF3)3AuPMe3.
- Sanner, Robert D.,Satcher Jr., Joe H.,Droege, Michael W.
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p. 1498 - 1506
(2008/10/08)
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- Infrared Multiphoton Dissociation of Heptafluoropropane
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The dissociation yield and branching ratio in CO2-laser-induced multiphoton dissociation (MPD) of CF3CF2CHF2 were studied as a function of irradiation frequency (979.7, 1037.4, and 1081.1 cm-1) and laser fluence (focal fluence 2).Br2 was successfully employed to reveal the dissociation mechanisms by scavenging a number of primary and secondary dissociation fragments produced in the MPD.At low laser fluences the distributions of scavenged products were the same regardless of irradiation frequencies.The primary dissociation of CF3CF2CHF2 was found to proceed mainly via the higher activation energy channels (i.e., C-C ruptures: CF3CF2CHF2 -> C2F5 + CHF2, and CF3CF2CHF2 -> CF3 + C2HF4) rather than via HF elimination (CF3CF2CHF2 -> C3F6 + HF) in our experimental conditions.The observed branching ratio between the two C-C rupture channels (ca. 2:1) agreed with the results obtained by RRKM calculation.A remarkable difference in product distribution with respect to the irradiation frequency was observed at higher laser fluences.This indicates that the secondary photolysis of primarily produced radicals within the laser pulse occured significantly at higher fluences (i.e., C2F5 -> CF3 + CF2, CHF2 -> CF2 + H, CF3 -> CF2 + F, and C2HF4 -> CF2 + CHF2), depending strongly upon the irradiation frequencies.
- Kato, Shuji,Makide, Yoshihiro,Tominaga, Takeshi,Takeuchi, Kazuo
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p. 4278 - 4284
(2007/10/02)
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- An Efficient Synthesis of N-Bromoperhalo-1-alkanimines
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Certain perhalogenated nitriles have been found to react readily with bromine and active cesium fluoride to afford high yields of N-bromoperhalo-1-alkanimines (RxFC=NBr; Rx = CF3, C2F5, n-C3F7, CF2Cl, CCl3).Photolysis of the perfluorinated N-bromo compounds affords the novel perfluoroazines RfFC=NN=CFRf.
- O'Brien, Brian A.,DesMarteau, Darryl D.
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p. 1467 - 1469
(2007/10/02)
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- Chemical Radical Synthesis in Gas Mixtures Induced by Infrared Multiple-Photon Dissociation
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Some experimental approaches to gas-phase radical chemical synthesis induced by the process of IR multiple-photon excitation of polyatomic molecules are considered.A comparison of laser and thermal initiation of gas-phase radical reaction is given.
- Bagratashvili, V. N.,Kuzmin, M. V.,Letokhov, V. S.
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p. 5780 - 5786
(2007/10/02)
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- Infrared Multiphoton Dissociation of Pentafluoroethane: Two-Channel Dissociation Process and Secondary Photolysis of Radical Products
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The dissociation yield and branching ratio in CO2 laser-induced multiphoton dissociation (MPD) of C2HF5 were investigated.In order to distinguish the two primary dissociation pathways (C2HF5 -> C2F4 + HF, Ea=71.6 kcal/mol; C2HF5 -> CF3 + CHF2, Ea=93.5 kcal/mol), Br2 was employed as an excellent scavenger of radicals and C2F4.The scavenged products were CBrF3, CHBrF2, CBr2F2, and C2Br2F4.The yield of C2Br2F4 originating from HF elimination was much smaller than those of CBrF3 and CHBrF2 from C-C bond rupture.The pulse energy dependence of the product distribution demonstrates that the primarily produced radicals were further photolyzed within the laser pulse (CF3 + nhν -> CF2 + F, and CHF2 + n'hν -> CF2 + H) to yield CBr2F2.The secondary photolysis of the radicals was also confirmed by real-time monitoring of infrared emission from HF* and DF* generated in the MPD of C2DF5 in the presence of H2 as an F atom scavenger.In the MPD of neat C2HF5, the formation of C2F4 was unexpectedly enhanced with increasing pulse energy; this was explained by assuming that C2F4 was mainly formed via recombination of CF2 radicals originating from the secondary photolysis of primarily produced radicals.
- Kato, Shuji,Makide, Yoshihiro,Takeuchi, Kazuo,Tominaga, Takeshi
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p. 3977 - 3981
(2007/10/02)
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- Kinetics and Mechanism of the Gas-phase Thermal Bromination of Trifluoromethane
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The kinetics of the gas-phase thermal bromination of trifluoromethane have been investigated in a dynamic regime over a wide range of concentration ratios of the reactants.In the temperature range 273 - 973 K and in the bromine mole fraction range 0.04 - 1 the reaction proceeds with one type of chain termination - via the recombination of bromine atoms.The rate of reaction is directly proportional to the concentration of trifluoromethane and is proportional to the square root of the bromine concentration.
- Zhdanov, G. F.,Poluektov, V. A.,Belevstev, E. G.,Orlov, G. D.
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p. 195 - 198
(2007/10/02)
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- Gasphase Reactions, 34. Ni/Pd Catalysed Gasphase Bromination of Trifluoromethane
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The reaction F3CH + Br2 -> F3CBr + HBr is an instructive example, how a multiparameter optimization has been accomplished by means of PE spectroscopic gas analysis.All reaction components can be monitored simultaneously and continuously via their ionization patterns.Measurement of the temperature dependence allows to judge on the quality of the catalysts tested.The fluorination of oxide carriers by trifluoromethane, a strong corrosive at temperatures above 600 K, is recognized by the appearance of the CO and HF PE bands.The heterogeneously catalyzed reaction perfected in millimole quantities at 10-2 mbar can be transferred to prepara tive scale.
- Bock, Hans,Wittmann, Joerg,Mintzer, Jan,Russow, Juergen
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p. 2346 - 2356
(2007/10/02)
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- Kinetics and Mechanism of the Joint Gas-phase Bromination and Chlorination of Trifluoromethane
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Preliminary data have been obtained for the kinetics of the joint bromination and chlorination of trifluoromethane.In the presence of chlorine bromination (the formation of bromotrifluoromethane) takes place preferentially.The addition of chlorine to the system greatly increases the rate of reaction.It is shown that the acceleration of the bromination in the presence of chlorine can be accounted for by the reaction between atomic bromine and molecular chlorine to give molecular chlorobromine and atomic chlorine, and also by the reaction of atomic chlorine with molecular bromine to form a molecule of chlorobromine and atomic bromine.Analytical expressions have been obtained for the rate of reaction as well as the ratio of bromotrifluoromethane and chlorotrifluoromethane formed.These expressions are consistent with experiment.
- Zhdanov, G. F.,Poluektov, V. A.,Belevtsev, E. G.,Orlov, G. D.
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p. 1135 - 1137
(2007/10/02)
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- Synthesis and properties of chlorine(I) and bromine(I) trifluoromethanesulfonates and Raman spectra of CF3SO2X (X = F, OH, OCl)
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The synthesis and characterization of the new hypohalites CF3SO3Cl and CF3SO3Br are described. Both compounds are thermally unstable at 22°C, decomposing to CF3Cl and SO3 for the hypochlorite and CF3SO3CF3, CF3SO2OSO2OCF3, SO3 and Br2 for the hypobromite. The hypochlorite is prepared by reaction of CF3SO3H with ClF and the hypobromite by reaction of CF3SO3Cl with bromine. The low-temperature Raman spectrum of CF3SO3Cl suggests C1 symmetry and assignments of 20 of the expected 21 fundamentals are given. These assignments were aided by an analysis of the Raman spectra of CF3SO2F and CF3SO2OH, which are reported for the first time.
- Katsuhara, Yutaka,Hammaker, Robert M.,DesMarteau, Darryl D.
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p. 607 - 615
(2008/10/08)
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- Synthesis of Haloalkyl Esters of Trifluoromethanesulfonic Acid by the Regio- and Stereospecific Addition of Chlorine(I) and Bromine(I) Trifluoromethanesulfonate to Alkenes
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The synthesis of a variety of haloalkyl esters of trifluoromethanesulfonic acid was achieved by the addition of CF3SO2OCl and CF3SO2OBr to alkenes.Addition to simple alkenes such as CH2CH2, CF2CH2, CF2CF2, CF2CFCl, CF2CCl2, CHClCHCl, and CHFCHF occur readily at low temperature to give the esters in high yield.With unsymmetrical alkenes, only one structural isomer is observed in every case.With the hypochlorite, cis- and trans-CHFCHF form a single different diastereomer.With the hypobromite, the same result is observed, and trans-CHClCHCl also gives only one diastereomer.A regio- and stereospecific cis-addition mechanism is proposed.
- Katsuhara, Yutaka,DesMarteau, Darryl D.
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p. 2441 - 2446
(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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