2264-21-3Relevant academic research and scientific papers
HEAT OF FORMATION OF THE CF2CL. RADICAL
LEYLAND LM,MAJER JR,ROBB JC
, p. 898 - 900 (1970)
The difference in the energies of activation, combined with known thermochemical data gives a value for the heat of formation of the CF//2Cl. radical of 64. 3 kcal and a value for D(CH//2Cl-H) of 103. 8 kcal. Combination of this value with the measured appearance potential of (CF//2Cl) cation from CF//2Cl//2 gives a value for the ionization potential of the CF//2Cl. radical of 9. 1 ev. Bond- dissociation energies in several molecules containing the CF//2Cl. radicals have been determined from the appropriate appearance potentials of (CF//2Cl) cation.
Crossed molecular beam studies of the reactions of methyl radicals with iodoalkanes
Robinson, Gary N.,Nathanson, Gilbert M.,Continetti, Robert E.,Lee, Yuan T.
, p. 6744 - 6752 (1988)
The I atom exchange reactions, CH3+RI->CH3I+R , were investigated at a collision energy of ca. 13 kcal/mol using the crossed molecular beams technique.The supersonic beam of methyl radicals was formed by pyrolyzing a mixture of ca. 1percent di-tert-butyl peroxide in helium in a quartz nozzle.A large fraction of the total energy available to the products from these reactions is channeled into relative translation suggesting that the dominant interaction among the products is repulsive.The CH3 I product from both reactions was observed to be entirely backward scattered with respect to the incident radical beam indicating that a roughly collinear C-I-C transition state geometry is favored.The present results are compared to those of earlier crossed beam studies of the CH3+IY->CH3I+Y (Y=Cl, Br, I) reactions; the differences observed among these reactions are explained with reference to the CH3I-Y and CH3I-R interaction potentials.
Competing pathways in the infrared multiphoton dissociation of hexafluoropropene
Longfellow,Smoliar,Lee,Lee,Yeh,Lin
, p. 338 - 344 (1997)
The infrared multiphoton dissociation of hexafluoropropene was studied by photofragment translational spectroscopy. Two primary channels and one secondary channel were identified. The predominant primary channel produces CF3CF or C2F4 and CF2, with the heavier species undergoing further dissociation to two CF2 fragments. A number of dissociation mechanisms are proposed for the elimination of CF2, including direct cleavage of the carbon - carbon double bond. In the second primary channel, a simple bond rupture reaction produces CF3 and C2F3. As expected, the translational energy distribution for this channel peaks near zero, indicating no exit barrier is present. The activation energy for this simple bond rupture is estimated to be 100-105 kcal/mol. The branching ratio, [CF2]/[CF3], between the two primary pathways is 4.0 ± 1.0.
Reactivity of Negative Ions with Trifluoromethyl Halides
Morris, Robert A.,Viggiano, A. A.,Miller, Thomas M.,Seeley, John V.,Arnold, Susan T.,et al.
, p. 10641 - 10645 (1996)
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.
Photoinduced Sulfur-Nitrogen Bond Rotation and Thermal Nitrogen Inversion in Heterocumulene OSNSO
Wu, Zhuang,Feng, Ruijuan,Xu, Jian,Lu, Yan,Lu, Bo,Yang, Tao,Frenking, Gernot,Trabelsi, Tarek,Francisco, Joseph S.,Zeng, Xiaoqing
, p. 1231 - 1234 (2018/02/09)
An exotic ternary S, N, O heterocumulene OSNSO in syn-syn (A) and syn-anti (B) conformations has been generated in the gas phase through flash vacuum pyrolysis of CF3S(O)NSO at 700 K. Upon visible light irradiation (570 ± 20 or 532 nm), both A and B, isolated in cryogenic matrices (N2, Ne, Ar, and Kr, a higher-energy anti-anti conformer (C). The reverse conformational transformation occurs either through S=N bond rotation (C to A and B) under visible light irradiation (400 ± 20 nm) at 2.8 K or through thermal nitrogen inversion (C to A) in the temperature range of 20-30 K, for which an exceptionally low activation barrier of 1.18 ± 0.07 kcal mol-1 has been experimentally determined.
An experimental and modelling study of ignition delays in shock-heated ethane-oxygen-argon mixtures inhibited by 2H-heptafluoropropane
Ikeda, Emi,Mackie, John C.
, p. 997 - 1009 (2007/10/03)
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.
FTIR spectroscopic study of 1,1,1-trifluoro-2-chloroethyl and 1,1,1- trifluoro-2-chloroethylperoxyl radicals
Baskir,Korolev,Nefedov
, p. 519 - 522 (2007/10/03)
A combination of matrix isolation and FTIR spectroscopy was applied to investigate 1,1,1-trifluoro-2-chloroethyl (1) and 1,1,1-trifluoro-2- chloroethylperoxyl (2) radicals. Radical 2 was obtained by vacuum pyrolysis of 1,1,1-trifluoro-2-bromo-2-chloroethane (3). Corresponding peroxyl radicals was generated by co-condensation of pyrolysis products and molecular oxygen in an argon matrix. To assign the experimental bands DFT calculations (B3LYP/6-311G**) were carried out. The fundamental bands of O-O and C-O stretching vibrations of peroxyl radical CF3CHClOO (1102.1, 972.7, cm-1) were identified by their red shifts to 1044.7 and 954.1 cm-1 in the spectra of 18O substituted derivatives. UV photolysis of the radical 2 in the low- temperature matrix produced difluoroformaldehyde CF2O, radicals ClCO, CF3, as well as CO and HCl as the primary photoproducts.
Kinetic study of the reactions of CF3O2 radicals with Cl and NO
Louis, Florent,Burgess Jr., Donald R.,Rayez, Marie-Therese,Sawerysyn, Jean-Pierre
, p. 5087 - 5096 (2007/10/03)
Kinetic studies of the reactions CF3O2 + Cl and CF3O2 + NO were performed at room temperature in the gas phase using the discharge flow mass spectrometric technique (DFMS). The reactions were investigated under pseudo- first-order conditions with Cl or NO in large excess with respect to the CF3O2 radicals. The rate constant for the reaction CF3O2 + NO was measured at 298 K and the value of (1.6 ± 0.3) x 10-11 cm3 molecule-1 s-1 is in very good agreement with all previous values. For the reaction CF3O2 + Cl, we obtain a rate constant at 298 K of (4.2 ± 0.8) x 10-11 cm3 molecule-1 s-1 in excellent agreement with the only published value. Product analysis shows that this reaction occurs via the major reaction pathway CF3O2 + Cl → CF3O + ClO at room temperature. In addition, an ab initio theoretical study was performed to gain insights on the different postulated reaction pathways. There is a significant disagreement between experimental and ab initio values recommended for the formation enthalpies of CF2O, CF3O and related molecules produced in this system. Consequently, we provide self-consistent values of enthalpies based on isodesmic reactions for the CF3O2 + Cl reaction system using the G2, G2(MP2) and CBS-Q methods. These values are also compared with BAC-MP4 heats of formation calculated in this work.
Products of the ultraviolet photodissociation of trifluoroacetic acid and acrylic acid
Osborne, Michael C.,Li, Qiang,Smith, Ian W. M.
, p. 1447 - 1454 (2007/10/03)
The photodissociation of trifluoroacetic and acrylic acids by the ultraviolet light from a flashlamp has been investigated by measuring the relative yields of some of the major products by time-resolved infrared absorption using tunable, narrow band diode lasers. Yields of CO2 were measured both in the absence and presence of added O2. The former experiments measure the CO2 produced directly by decarboxylation of the acid, channel (2) below, the latter the sum of the yields from channels (1) and (2) since HOCO is rapidly converted to CO2. The yields of CO from the decarbonylation channel (3) have also been measured. For trifluoroacetic acid, the relative yields are found to be [HOCO]: [CO2]: [CO] = (0.28 ± 0.07): (0.61 ± 0.09): (0.11 ± 0.06) and, for acrylic acid, [HOCO]: [CO2]: [CO] = (0.32 ± 0.08): (0.37 ± 0.08) :(0.31 ± 0.09). The results are discussed in relation to the other, limited, measurements on the photodissociation of these acids and whether these three processes are likely to occur independently of one another.
Infrared multiphoton dissociation of two perfluorobutenes
Longfellow, Cheryl A.,Berrie, Cindy L.,Suits, Arthur G.,Lee, Yuan T.
, p. 7202 - 7208 (2007/10/03)
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.
