- Shock-Wave Study of the High-Temperature UV Absorption and the Recombination of CF3 Radicals
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The high-temperature UV absorption and the recombination of CF3 radicals have been investigated in shock-wave experiments.CF3 radicals were produced near 1300 K in the fast dissociation of (CF3)2N2 and of CF3NO.At pressure of the bath gas Ar between 0.3 and 25 atm, the recombination was found to be in the unimolecular falloff range closer to the high than to the low pressure limit.Extrapolation to the high pressure limit gives krec,infinite(CF3)=(1.9+/-0.9)E13 cm3 mol-1 s-1 at T=1300 K.Earlier low-temperature results are compared with the present data by using unimolecular rate theory.
- Glaenzer, K.,Maier, M.,Troe, J.
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- Fluorinated acetylenes. Part 8. Preparation and some reactions of 5,5,5-trifluoropent-3-yn-2-ol, 5,5,5-trifluoro-1-phenylpent-3-yn-2-ol and the derived ester, 2-acetoxy-5,5,5-trifluoropent-3-yne
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Treatment of the salt CF3CCLi (3) with the aldehydes RCH2CHO (R = H and Ph) affords the secondary alcohols CF3CCCHROH (1a) R = Me and (1b) R = CH2Ph.Alcohol 1a does not give the corresponding ketone on attempted oxidation (pyridinium chlorochromate or Na2Cr2O7/H2SO4), but alcohol 1b is oxidized to the diketone (CF3CCCOCHPh)2 (7) (41percent) by active MnO2.The acetate CF3CCCHMeO2CMe (2) undergoes facile reaction with diazomethane to give 3--1-methyl-4-trifluoromethylpyrazole (10a) and hence the 3- and 5--1-methyl-4-trifluoromethylpyrazoles (11a) and (12a), respectively.Cycloaddition also takes place between ester 2 and furan, but the major products (considered to be isomeric 1:1 adducts) have not been fully characterised.Although, ester 2 undergoes reaction with trifluoronitrosomethane, a cycloadduct has not been isolated, while nucleophilic attack by imidazole on the triple bond leads to the (Z)-alkene (18).
- Sibous, Lakhdar,Tipping, Anthony E.
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- On the reaction of perfluoro-aza-propene with oxygen difluoride and fluorination of bis(trifluoromethyl)-hydroxylamine
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The reactions of perfluoro-aza-propene CF3NCF2 with an excess of oxygen difluoride OF2 and the fluorination of bis(trifluoromethyl)-hydroxylamine (CF3)2NOH are discussed. Additionally, we present density functional calculations (B3LYP/6-31G*) on bis(trifluoromethyl)-hypofluorite (CF3)2NOF, which clearly show that this molecule is a model substance for the discussion of negative hyperconjugation.
- Minkwitz, Rolf,Reinemann, Stefan,Ludwig, Ralf
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- INTRACAVITY ABSORPTION OF He-nE-LASER RADIATION AS A DIRECT TIME-RESOLVED PROBE OF R + NO -> RNO REACTION KINETICS (R = C3F7, CF3, CH3)
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The reaction of NO with C3F7, CF3 and CH3 have been studied at room temperature using laser flash photolysis coupled with time-resolved product absorption.The pressure dependent rate coefficients were extrapolated using the Troe procedure to provide estimates of k0 and kinfinite.
- Vakhtin, A. B.,Petrov, A. K.
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- Perfluoroalkylation of simple inorganic molecules: A one step route to novel perfluoroalkylated compounds
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Reactions of (CH3)3SiRf (Rf = CF3, C2F5) with NOCl, NO/NO2, SO2, CO2, in the presence of caesium fluoride provide a one step synthetic route to perfluoroalkylated compounds in very good yields.
- Singh, Rajendra P.,Shreeve, Jean'ne M.
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- Neue Syntheseverfahren fuer Nitrosoperfluoralkane CnF(2n+1)NO (n = 1, 2, 3, 6)
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Perfluoronitrosomethane, CF3NO, may be isolated in ca. 50percent yield of a reaction mixture of i-C3H7ONO2 with ZnBr(CF3)*2CH3CN in the presence of aluminium trichloride.Approximately quantitative yields of CnF(2n+1)NO (n = 1, 2, 3, 6) may be obtained by reacting NOCl with Cd(CnF(2n+1))2*glyme.The preparations are described. - Keywords: Perfluoronitrosoalkanes; Syntheses; F-Alkylcadmium complexes
- Ludovici, K.,Naumann, D.,Siegemund, G.,Tyrra, W.,Varbelow, H.-G.,Wrubel, H.
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- DIE REAKTION VON (CF3)2Cd*D MIT (CH3)Sn(ONO2): EIN NEUES DARSTELLUNGSVERFAHREN FUER CF3NO
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CF3NO is formed from the reaction of (CH3)3Sn(ONO2) with (CF32Cd*diglyme at room temperature as the only volatile product in 60 percent yield.
- Lange, Horst,Naumann, Dieter
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- The reaction of perfluoro-2,5-diazahexane 2,5-dioxyl with aromatic compounds and perfluoroiodoalkanes
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Treatment of perfluoro-2,5-diazahexane 2,5-dioxyl (1) with the fluoroarenes C6F5X (X = F or Br at c. 20 deg C; X = CF3 at 50 deg C) and pentafluoropyridine (50 deg C) gives 2:1 copolymers in high yield, but pentachloropyridine is unreactive at 50 deg C.Copolymers are also formed between 1 and the arenes C6F5I, C6F5H and C6H6 which did not analyse correctly for 2:1 copolymers; in the latter case, hydrogen abstraction is taking place as shown by the presence of N-OH and C=O groups in the polymer.Hexafluorobenzene is not incorporated in the polymer formed by treatment of 1 with a mixture of vinylidene fluoride and hexafluorobenzene.Photochemical reaction of trifluoroiodomethane with 1 affords the bishydroxylamine CF3ON(CF3)CF2CF2N(CF3)OCF3 in quantitative yield, while the di-iodides I(CF2)nI (n = 2 and 4) give copolymers of 1 and the units (CF2)n (n = 2 and 4), which contain (CF2)nI end-groups.
- Green, Michael J.,Tipping, Anthony E.
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- Photochemistry of matrix isolated (Trifluoromethyl)sulfonyl azide, CF3SO2N3
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The photochemistry of matrix isolated (trifluoromethylsulfonyl) azide, CF3SO2N3, has been studied at low temperatures. Upon ArF laser irradiation (λ = 193 nm), the azide eliminates N2 and furnishes triplet [(trifluoromethyl)sulfonyl]nitrene, CF3SO2N, which has been characterized by IR and EPR spectroscopy. Upon subsequent UV light irradiation (λ = 260-400 nm) the nitrene converts to CF3N=SO2 and CF3S(O)NO through a Curtius-type rearrangement. Further two new species CF2N=SO2F and FSNO were identified together with CF2NF, SO2, F2CO, CF3NO, and SO as side products. In addition, triplet nitrene CF3N was detected by its EPR and IR spectra. The complex stepwise photodecomposition of matrix isolated CF3SO2N3 is discussed in terms of the observed photolysis products and quantum chemical calculations.
- Zeng, Xiaoqing,Beckers, Helmut,Willner, Helge,Neuhaus, Patrik,Grote, Dirk,Sander, Wolfram
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p. 2281 - 2288
(2015/03/30)
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- Reactivity of Negative Ions with Trifluoromethyl Halides
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The kinetics of the reactions of selected anions (A(-)) with the trifluoromethyl halides CF3X (X = F, Cl, Br, I) in the gas phase were measured at 300 K.Reaction rate constants and product branching fractions were determined using a selected ion flow tube (SIFT) instrument.The chosen anions were C5F5N(-), o-, m-, and p-CF3C6H4CN(-), C6F5Br(-), C6F5Cl(-), C6F5CF3(-), C6F5COCH3(-), Fe(-), FeCO(-), SF6(-), SO(-), SO2(-), NO(-), NO2(-), and NO3(-).The reactivity of these systems varies from unreactive to collisional, and a variety of reaction types was found.The results of our present and previous measurements on A(-) + CF3X reactions show that, in cases where nondissociative electron transfer (NDET) is energetically allowed, the total reactivity tends to be high, approaching collisional.This suggests that reactivity in these cases is initiated and controlled by electron transfer from the anion.In addition, association reactions tend to be preempted when NDET is energetically allowed.A few exceptions to these tendencies were found and are discussed.
- Morris, Robert A.,Viggiano, A. A.,Miller, Thomas M.,Seeley, John V.,Arnold, Susan T.,et al.
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p. 10641 - 10645
(2007/10/03)
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- Photolysis of CF3NO as a source of CF3 radicals, rate constant of the CF3 + CF3NO reaction at 296 K
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The linear absorption cross-sections and photodissociation quantum yields for CF3NO have been measured at the wavelengths 694,3 and 632.8 nm (ruby and He - Ne lasers, respectively) in a wide range of total pressure at T = 296 K. The secondary reactions following the photolysis of CF3NO have been studied. The rate constant of the CF3 + CF3NO reaction has been measured. The results obtained show CF3NO photolysis be a convenient source of CF3 radicals for kinetic studies.
- Garmanov,Vakhtin
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- UV Absorption Cross Sections of Acetyl Peroxynitrate and Trifluoroacetyl Peroxynitrate at 298 K
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The UV absorption cross sections of acetyl peroxynitrate (PAN) and trifluoroacetyl peroxynitrate (FPAN) were determined at 298 K in the wavelength ranges 220-325 nm and 230-305 nm, respectively.Both peroxynitrates were prepared from nitric acid and the corresponding peroxy acids in n-tridecane solution.The UV spectra were measured in a large cell (v = 420 dm3) equipped with White mirror systems for the simultaneous detection of gas phase species by long-path UV and IR absorption.Impurities in the samples were quantified by their IR and/or UV absorption, and the UV spectra were corrected for contributions from these impurities using appropriate reference spectra.Concentrations of acetyl peroxynitrate and trifluoroacetyl peroxynitrate were derived from their IR absorptions by application of Beer's law.IR absorption coefficients were determined based on pressure measurements of the pure compound (for PAN) or on the stoichiometric CO2 yield in the thermal decomposition of the peroxynitrate in the presence of NO and O2 (for FPAN).The resulting UV absorption cross sections of PAN are larger than literature values, leading to photolysis rate constants on the Earth's surface which are higher by a factor of 4 than previous values (Senum et al., 1984).The absorption cross sections of FPAN were measured for the first time and result in photolysis rate constants which are slightly higher than those of PAN, suggesting that CF3C(O)O2NO2 and, by analogy, other haloacetyl peroxynitrates have too short a lifetime in the upper troposphere to be of importance for the transport of halogens into the stratosphere. - Keywords: Atmospheric Chemistry / Light, Absorption / Photochemistry / Spectroscopy, Ultraviolet
- Libuda, H. G.,Zabel, F.
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p. 1205 - 1213
(2007/10/02)
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- Kinetic Study of the Reaction of Chlorine Atoms with CF3I and the Reactions of CF3 Radicals with O2, Cl2 and NO at 296 K
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The kinetics of the gas-phase reaction of Cl atoms with CF3I have been studied relative to the reaction of Cl atoms with CH4 over the temperature range 271 - 363 K.Using k(Cl + CH4) = 9.6*10-12 exp(-2680/RT) cm3 molecule-1 s-1, we derive k(Cl + CF3I) = 6.25*10-11 exp(-2970/RT) in which Ea has units of cal mol-1.CF3 radicals are produced from the reaction of Cl with CF3I in a yield which was indistinguishable from 100percent.Other relative rate constant ratios measured at 296 K during these experiments were k(Cl + C2F5I)/k(Cl + CF3I) = 11.0 +/- 0.6 and k(Cl + C2F5I) /k(Cl + C2H5Cl) = 0.49 +/- 0.02.The reaction of CF3 radicals with Cl2 was studied relative to that with O2 at pressures from 4 to 700 torr of N2 diluent.By using the published absolute rate constants for k(CF3 + O2) at 1-10 torr to calibrate the pressure dependence of these relative rate constants, values of the low- and high-pressure limiting rate constants have been determined at 296 K using a Troe expression: k0(CF3 + O2) = (4.8 +/- 1.2)*10-29 cm6 molecule-2 s-1; kinfinite(CF3 + O2) = (3.95 +/- 0.25)*10-12 cm3 molecule-1 s-1; Fc = 0.46.The value of the rate constant k(CF3 + Cl2) was determined to be (3.5 +/- 0.4)*10-14 cm3 molecule-1 s-1 at 296 K.The reaction of Cl atoms with CF3I is a convenient way to prepared CF3 radicals for laboratory study.
- Kaiser, E. W.,Wallington, T. J.,Hurley, M. D.
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p. 205 - 218
(2007/10/02)
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- Reaction of bis(trifluoromethyl)amino-oxyl with alkylchlorosilanes and allyldichloro(methyl)silane and of perfluoro-2,5-diazahexane 2,5-dioxyl with vinylsilanes and hydrolysis of the products
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Treatment of the silanes MeSiHCl2, Me2SiHCl and EtSiMeCl2 with the oxyl (CF3)2NO(.) (1) gives the substitution products (CF3)2NOSiMeCl2 (4) and (CF3)2NOSiMe2Cl (5), and a mixture of (CF3)2NOCHMeSiMeCl2 (8) and (CF3)2NOCH2CH2SiMeCl2 (9) (ratio 20:37), respectively, while the silane EtSiMe2Cl affords mainly the ester (CF3)2NO2CMe (7).Attack of oxyl 1 on the silane CH2=CHCH2SiMeCl2 results in both allylic substitution and addition to give the compounds CH2=CHCH(SiMeCl2)ON(CF3)2 (14) and (CF3)2NOCH2CH(CH2SiMeCl2)ON(CF3)2 (15) (ratio 56:40).Reaction of the dioxyl (.)ON(CF3)CF2CF2N(CF3)O(.) (2) with the vinylsilanes CH2=CHSiX3 (X3 = Me3, Cl3, MeCl2) gives mainly 1:1 copolymers n (17), although the cyclic 1:1 adduct (18) is also formed in low yield.Hydrolysis of the silanes 15, (CF3)2NOCH2CH(SiMeCl2)ON(CF3)2 (19a) and (CF3)2NOCH2CH(SiCl3)ON(CF3)2 (19b) affords the corresponding polysiloxanes 24 and 25, and the polysilsesquioxane 26, respectively; the polymers 25 and 26 undergo rearrangement of the type -CH(Si)ON(CF3)2 --> -CH(OSi)N(CF3)2 on storage.The 1:1 copolymers 17b (X3 = MeCl2) and 17c (X3 = Cl3) are also hydrolysed to the corresponding siloxane and silsesquioxane polymers.In contrast, hydrolysis of the compounds 4,5 and (CF3)2NOCH2CH(OSiX3)N(CF3)2 (20a; X3 = MeCl2) and (20b; X3 = Cl3) results in Si-O bond cleavage.
- Tipping, Anthony E.,Yadav, Rajendraprasad B.
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- The reaction of perfluoro-2,5-diazahexane 2,5-dioxyl with alkenes
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The liquid-phase reaction at room temperature of the title dioxyl (1) with an excess of the alkenes CH2=CHR (R = H, F, COCl), CF2=CHF, CHCl=CCl2 and cis-CHCl=CHCl gives 1:1 copolymers 3 in high yield, although with the alkenes CH2=CH2, CH2=CHF and CF2=CHF cyclic 1:1 adducts 2 are also formed in low yield.The reactions with the alkenes CH2=CMe2, CH2=CHEt, CH2=CHCO2H, and cis-HO2CCH=CHCO2H produce copolymers which are not 1:1 copolymers.The 1:1 copolymer 3f from acryloyl chloride is hydrolysed readily by water to the acrylic acid/dioxyl 1 1:1 copolymer 3j.Gas-phase reaction at room temperature of 1 with an excess of the alkenes CH2=CHR (R=Cl, Br, COCl, COF), CH2=CXCH3 (X = Cl, Br), CHCl=CCl2, cis- and trans-CHCl=CHCl, CH2=CCl2, CF2=CCl2, CF2=CFCl and CF2=CFBr affords cyclic 1:1 adducts 2 (11.5-78percent) and copolymers 3 (18.5-76.5percent): hydrolysis of the acryloyl fluoride 1:1 adduct 2j gives the acrylic acid 1:1 adduct 2s in high yield.
- Green, Michael J.,Tipping, Anthony E.
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p. 115 - 126
(2007/10/02)
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- GENERATION OF 15N LABELLED BIS(POLYFLUOROALKYL)NITROXIDES AND THEIR HYDROGEN-ABSTRACTION REACTIONS WITH ALKANES, ALKYLBENZENES AND ALDEHYDES
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Blue solutions containing 15N labelled bis(polyfluoroalkyl) nitroxides and spin traps, polyfluoronitrosoalkanes, were conveniently made from the reactions of Na15NO2 with polyfluoro-compounds, (RFCO2), RFI and RFSO2Br in F113.It has been found that the nitroxides effected fast H-abstraction from alkanes, alkylbenzenes, aldehydes and the radicals derived from the substrates were in turn effectively trapped by RF15NO to give 15N labelled spin adducts detectable by ESR.The bigger aN(15N) values as well as much simpler splittings of both the nitroxides and the spin adducts have made the kinetic studies of the H-abstraction and other radical reactions quite feasible.
- Zhao, Cheng-Xue,Chen, Guo-Fei,Jiang, Xi-Kui
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p. 391 - 398
(2007/10/02)
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- Reactions of Perfluoronitroxides with Sulphur Dioxide
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Perfluoro-2,5-diazahexane 2,5-dioxyl reacts with sulphur dioxide and with sulphur tetrafluoride to give the 1 : 1 cyclic adducts perfluoro(4,7-dimethyl-1,3-dioxa-2-thia-4,7-diazacycloheptane 2,2-dioxide) and perfluoro(4,7-dimethyl-1,3-dioxa-2-tetrafluorothia-4,7-diazacycloheptane), respectively.Perfluoro(4,7-dimethyl-1,3-dioxa-2-thia-4,7-diazacycloheptane 2,2-dioxide) which oxidises iodide ion to iodine at room temperature, is stable to hydrolysis by aqueous potassium hydroxide at 120 deg C.It is stable to u.v. irradiation, but flow pyrolysis at 350 deg C and ca. 1 mmHg pressure gives trifluoronitrosomethane, perfluoro(2-methyl-1,2-oxazetidine), carbonyl fluoride, perfluoro(N-methylenemethylamine), and sulphur dioxide.It reacts with triphenylphosphine to give perfluoro(3,6-dimethyl-1-oxa-2-thia-3,6-diazacyclohexane 2,2-dioxide), perfluoro(2,5-dimethyl-1-thia-2,5-diazacyclopentane 1,1-dioxide) and triphenylphosphine oxide.Bis(trifluoromethyl) nitroxide reacts with sulphur dioxide to give the 2 : 1 adduct perfluoro(2,6-dimethyl-3,5-dioxa-4-thia-2,6-diazaheptane 4,4-dioxide), flow pyrolysis of which at 350 deg C and ca. 1 mmHg gives only bis(trifluoromethyl) nitroxide and sulphur dioxide.Perfluoro(2,4-dimethyl-3-oxa-2,4-diazapentane) reacts with sulphur dioxide giving perfluoro(2,5-dimethyl-3-oxa-4-thia-2,5-diazahexane 4,4-dioxide).
- Arfaei, Ahmad,Smith, Sydney
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p. 1791 - 1794
(2007/10/02)
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- SYNTHESIS AND REACTIVITY OF TRIFLUOROMETHYLAZOSULFONYLARENES
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Trifluoromethylazosulfonylarenes were synthesized in high yields by treatment of trifluoronitrosomethane with arenesulfonamides in the presence of a base and their reactivity was examined.It was found that they acted as effective hydrogen-acceptors as well as trifluoromethylating agents.
- Sekiya, Akira,Umemoto, Teruo
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p. 1519 - 1520
(2007/10/02)
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