116-14-3Relevant academic research and scientific papers
INFRARED LASER INDUCED DECOMPOSITION OF HEXAFLUOROBENZENE AND SOME MONOSUBSTITUTED DERIVATIVES. INTERMEDIACY OF THE PENTAFLUOROPHENYL RADICAL.
Watanabe, Akio,Koga, Yoshinori,Sugawara, Ko-ichi,Takeo, Harutoshi,Fukuda, Kenzo,Matsumura, Chi
, p. 463 - 469 (1990)
The infrared multiphoton laser induced reactions of hexafluorobenzene and related pentafluoro analogues (pentafluorobenzene, pentafluorochlorobenzene, pentafluorobromobenzene, and pentafluoroiodobenzene) have been investigated using a CO2 TEA laser.The study was carried out in order to define the decomposition products and to attempt to clarify their mode of formation.Thus, the products (relative yield, percent) of the irradiation of C6F6 (1027.3 cm-1; 0.73 J/cm2; 10 pulses; 25percent decomposition) were C2F4(64), C6F5CF3(28), C2F6(7), CF4(1) and that for C6F5H (949.4 cm-1; 0.80 J/cm2; 10 pulses; 25percent decomposition) was C2F4 and C6F5CF3.Increasing the number of pulses in the reaction with C6F6 decreased the amount of C2F4 and increased the amount of C6F5CF3 and C2F6 indicating secundary and tertiary reactions.Addition of halogen (X2, X = Cl, Br) to these reactions caused different products to be formed.Thus, the irradiation of a C6F6/Cl2 mixture (7.4/7 Torr; 1027.3 cm-1; 0.7 J/cm2; 35 pulses; 35percent reaction) afforded C6F5Cl(46); CF3Cl(24) and CF2Cl2(30).Irradiation of C6F5H/X2 mixtures afforded mainly C6F5X + HX.For example C6F5H/Br2 (10/40 Torr; 949.4 cm-1; 0.93 J/cm2; 10 pulses; 10percent reaction) gave C6F5Br and HBr exclusively.Irradiation of C6F5-X (X = Cl, Br, I) (977.2 cm-1; ca. 0.74 J/cm2; 200 pulses; 39-74percent reaction) gave C6F6 and a minor amount of decafluorobiphenyl , a radical combination product of the pentafluorophenyl radical (C6F5.).Increasing the fluence in these reactions gave similar products in most cases but in some instances increased the amount of C2F4 formed.The reactions and product distribution of the hydrogen substituted derivative (C6F5H) was examined in the presence of Br2 as a function of laser fluence and halogen concentration.It was found that the threshold for C6F5H decomposition was higher for the reaction involving Br2 (as compared with the reaction involving Cl2 or neat C6F5H).The presence of Br2 also decreased the amount of C6F5H that was decomposed, indicating a quenching process.The decomposition path with the lowest activation energie for these molecules is thought to be C6F5X -> C6F5. + X. and was accessible using a laser pulse with a fluence as low as 0.7 J/cm2.Using a higher laser fluence (ca. 1.2 J/cm2) di- and triatomic radicals were defined by spectroscopic identification of the and :CF2 species.These reactions are discussed in light of the formation of the C6F5. radical during a primary, laser induced, process.Subsequent decomposition to smaller fragments, combination with other radicals or scavenging by added reagents also takes place depending on the reaction conditions.
Infrared Laser Multiphoton Dissociation of CF2ClCH2Cl
Yano, T.,Ozaki, S.,Ogura, H.,Tschuikow-Roux, E.
, p. 1108 - 1116 (1985)
The infrared multiphoton decomposition (IRMPD) of CF2ClCH2Cl was studied with focusing geometry using the P(34) line of the 9.6-μm CO2 band (1033.6 cm-1).The principal reaction product is CF2CHCl.Other products of significance include CFClCHCl, CF2CH2, and CFCH.It is concluded that the primary processes of photodecomposition involve the molecular elimination of HCl and HF and, to a very minor extent, C-C bond rupture.The relative importance of the primary steps is approximately 1000:30:1, respectively.From a series of diagnostic experiments in the presence of hydrogen donors and D2, it is shown that CF2CH2 derives from the secondary photolysis of CF2CHCl.The decomposition yield, the HF/HCl ratio, and the CF2CH2/CF2CHCl ratio were investigated as a function of reactant and argon pressure, the latter serving as a buffer gas.From the dependence of the decomposition yield on pulse number at different pulse energies, E0, the specific rate of decomposition, b, was found to be proportional to b E01.8, the power dependence being somewhat higher than the standard 3/2 power law for focusing geometry.These phenomena are interpreted in terms of a simple geometric fluence model which includes contributions from collisionally induced reactions in the outermost (lower fluence) irradiated region.The nonresonant photodecomposition of C2H6 and C2H4 at 1033.6 cm-1 observed in auxiliary, diagnostic experiments is interpreted in terms of photosensitization processes.
Difluorocarbene studied with threshold photoelectron spectroscopy (TPES): Measurement of the first adiabatic ionization energy (AIE) of CF2
Innocenti, Fabrizio,Eypper, Marie,Lee, Edmond P. F.,Stranges, Stefano,Mok, Daniel K. W.,Chau, Foo-Tim,King, George C.,Dyke, John M.
, p. 11452 - 11460 (2008)
The first photoelectron band of difluorocarbene CF2, has been studied by threshold photoelectron (TPE) spectroscopy. CF2 was prepared by microwave discharge of a flowing mixture of hexafluoropropene, C3F6, and argon. A vibrationally resolved band was observed in which at least twenty-two components were observed. In the first PE band of CF2, the adiabatic ionization energy differs significantly from the vertical ionization energy because, for the ionization CF 2+ (X2A1)+e- ← CF2 (X1A1), there is an increase in the FCF bond angle (by ≈20°) and a decrease in the C-F bond length (by ≈ 0.7 A). The adiabatic component was not observed in the experimental TPE spectrum. However, on comparing this spectrum with an ab initio/Franck-Condon simulation of this band, using results from high-level ab initio calculations, the structure associated with the vibrational components could be assigned. This led to alignment of the experimental TPE spectrum and the computed Franck-Condon envelope, and a determination of the first adiabatic ionization energy of CF2 as (11.362± 0.005) eV. From the assignment of the vibrational structure, values were obtained for the harmonic and fundamental frequencies of the symmetric stretching mode (v1′) and symmetric bending mode (v2′) in CF2+ (X2A1).
CF3Br-H2 reaction in shock waves
Hidaka,Nakamura,Kawano
, p. 983 - 993 (1993)
CF3Br-H2 mixtures highly diluted with Ar were studied by using a time-resolved IR-emission of HBr and a gas-chromatography for reaction products. The temperature range covered was 1000-1600 K and the total pressure behind the reflected shock waves used was 1. 2-2.6 atm. CF3H, C2F6, and C2F4 were produced and the yields of these products were determined as a function of temperature. The main product under our experimental conditions was CF3H. The mechanism and the rate constants of CF3Br--H2 reaction at high temperatures were discussed. The experimental data was satisfactorily modeled using a 14-reaction mechanism. Reaction (5) played an important role in the formation of CF3H together with reaction (4).
Infrared multiphoton dissociation of two perfluorobutenes
Longfellow, Cheryl A.,Berrie, Cindy L.,Suits, Arthur G.,Lee, Yuan T.
, p. 7202 - 7208 (1997)
Photofragment translational spectroscopy was used to examine the infrared multiphoton dissociation of octafluoro-1-butene and octafluoro-2-butene. The predominant unimolecular reaction in octafluoro-1-butene at moderate laser fluences is cleavage of a carbon-carbon single bond to give the products CF3 and C3F5. The two other reactions that take place are CF2 elimination and the formation of equal weight fragments with the chemical composition C2F4; both reactions take place via a diradical intermediate. Dissociation of octafluoro-1-butene to the resonance stabilized perfluoroallyl radical is suggested to account for the favoring of simple bond rupture. These three reaction pathways were also observed in octafluoro-2-butene dissociation, however, the branching fraction is different than from octafluoro-1-butene. In octafluoro-2-butene all three channels occur with roughly equal probability. The reactions involving CF2 loss and C2F4 formation in octafluoro-2-butene are thought to proceed through the same diradical intermediate as in octafluoro-1-butene, necessitating a 1,2-fluorine migration.
Picosecond photofragment spectroscopy. IV. Dynamics of consecutive bond breakage in the reaction C2F4I2 -> C2F4 + 2I
Khundkar, Lutfur R.,Zewail, Ahmed H.
, p. 231 - 242 (1990)
Picosecond photofragment spectroscopy of the ultraviolet (UV) photodissociation of 1,2-diiodotetrafluoroethane reveals consecutive breaking of the two C-I bonds.Spin-orbit excited (I*) atoms show a prompt rise, in agreement with a direct mode dissociation of the first bond.Ground-state (I) atoms show a biexponential buildup, one component being fast (1 ps) while the other component is slow (30-150 ps depending on total energy), characteristic of the second bond breaking.The transient behavior of I atoms changes with the available energy.These results are interpreted in terms of a two step model involving a weakly bound radical.Simulations of transient behavior of I atoms, based on estimated internal energy distributions from the primary step and a model for dissociation rates as a function of energy, suggest that surface crossings are relevant to the dynamics and that the quantum yield of I atoms varies with excitation energy.
Multiphoton Excitation of trifluoroethene. Allene Production by Difluorovinylidine
Stachnik, Robert A.,Pimentel, George C.
, p. 2205 - 2210 (1984)
Trifluorethene was excited with a high-power, pulsed CO2 laser, and the products were analyzed by mass and infrared spectroscopy.Mainly, this initiates αα elimination of HF to produce difluorovinylidine, CCF2.This species adds across the double bond of another parent molecule followed by deactivation or release of CF2 and carbon insertion to produce trifluoroallene and C2F4.In the presence of other olefins, C2H4, C2D4, and C2F4, multiphoton excitation of trifluoroethene forms respectively allene, perdeuterioallene, and perfluoroallene.In the presence of cyclopentadiene, carbon insertion seems to take place, but benzene is not formed.In these experiments, some olefin products show that when a vibrationally excited trifluoroethene molecule collides with another olefin, metathesis can take place, presumably through a cyclobutane intermediate.
DEPENDENCE OF THE UNIMOLECULAR DISSOCIATION PRODUCTS ON THE FLUENCE OF THE CO2 LASER BEAM
Santos, M.,Hernandez-Vara, R.,Herreros, J. M.,Gonzales-Diaz, P. F.
, p. 533 - 536 (1986)
The dissociation products of CF2Cl2 irradiated in the line P20 at 9.17 μm with pulses of fluence as high as 60E4 J*m-2 depend on the pressure of the gas, giving rise to C2F4 only when the pressure is of the order of 2 mb.At remarkably lower fluence (2E4 J*m-2) this product appears however in a wide range of pressures. For CF2HCl, C2F4 is the only product that appears at fluences as high as 60E4 J*m-2).At lower fluences (2.5E4 J*m-2), less C2F4 is produced and another product, probably a halogenated derivative of butane, is obtained.
Isothermal pyrolysis of iodomethanes in gases
Skorobogatov,Khripun,Rebrova
, p. 2641 - 2651 (2009)
The fact was established that the pyrolysis of gaseous iodomethanes RI yields methane and non traces of recombination products R2. A pyrolysis mechanism was proposed and rate constants of limiting stages of the pyrolysis of iodomethane, trideuteroiodomethane, and diiodomethane over the range of 500-1500 K were determined. Pleiades Publishing, Ltd., 2009.
Highly selective photochemical synthesis of perfluoroalkyl bromides and iodides
Zhang,Zhang,Yang,Wang,Fuss,Weizbauer
, p. 153 - 168 (1998)
Highly fluorinated alkyl iodides are conveniently synthesized by telomerization of a fluoroalkyl-iodide, RI, with, e.g., C2F4. Normally, the reaction, often carried out in the liquid phase with a radical initiator, gives products with a broad distribution of molecular weights. In this work, we report a method that obtains selectively products of a desired molecular weight: this method is a photochemically induced reaction in the gas phase; the gas is circulated through a trap or a rectification still which continuously removes the heavier products, whereas the more volatile molecules return to the photoreactor. An analysis by rate equations shows which control parameters are important, and by a suitable choice of these parameters, we obtained a better selectivity for, e.g., C8F17I than previously. This method also works with BrC2F4Br instead of an iodide. In this case, we demonstrated in a small laboratory setup with simple low-pressure Hg lamps (5 × 30 W), a productivity of more than 0.5 kg/day. In the telomerization of CF3Br or HC2F4Br with C2F4 we found, however, a few percent of dibromide side products which are sometimes difficult to separate because of similar boiling points. For this case, it is better to synthesize the iodides instead, and then exchange the I for Br, if desired.
