3474-12-2Relevant articles and documents
Halogen abstraction reaction between aminoalkyl radicals and alkyl halides: Unusual high rate constants
Lalevée,Allonas,Fouassier
scheme or table, p. 415 - 418 (2009/02/02)
The very high reactivity of aminoalkyl radicals toward the halogen abstraction reaction is reported for the first time. Reaction rate constants with CCl4 and CBr4 are close to the diffusion limit: they are about 4-5 orders of magnitude higher than those previously determined for typical alkyl radicals. A better understanding of this unusual behavior is obtained using molecular orbitals (MO) calculations. The participation of polar effects is directly evidenced. This approach can be useful for the design of new reducing agents.
Kinetics of reactions of CN with chlorinated methanes
Samant, Vaishali,Hershberger, John F.
experimental part, p. 64 - 67 (2009/02/04)
The kinetics of reactions of CN with the chlorinated methanes CH3Cl, CH2Cl2, CHCl3 and CCl4 were investigated over the temperature range 298-573 K, using laser induced fluorescence (LIF) spectroscopy. At 298 K, rate constants of 9.0 ± 0.3 × 10-13, 8.8 ± 0.4 × 10-13, 9.0 ± 0.5 × 10-13 and 4.3 ± 0.6 × 10-13 cm3 molecule-1 s-1 were measured, respectively. A small positive temperature dependence was observed, as well as kinetic isotope effects of kH/kD ～ 2.14-2.25. These data along with product detection experiments strongly suggest that hydrogen abstraction dominates these reactions.
FTIR and computational studies of gas-phase hydrogen atom abstraction kinetics by t-butoxy radical
Li, Shuping,Fan, Wai Yip
, p. 276 - 280 (2007/10/03)
By using Fourier-Transform Infrared (FTIR) absorption spectroscopy, rate coefficients in the range of 10-16 to 10-14 cm3 molecule-1 s-1 have been determined for the hydrogen atom abstraction reactions of several substrates including halogenated organic compounds and amines by t-butoxy radical generated from the uv photolysis of t-butyl nitrite in the gas phase. Arrhenius parameters for selected reactions have been measured in the temperature range 299-318 K. Transition states and activation barriers for such reactions have been computed with the help of Gaussian 03 software and found to match very well with the experimental values.
Temperature dependence of the rate coefficients for the reaction of chlorine atoms with chloromethanes
Orlando, John J.
, p. 515 - 524 (2007/10/03)
Rate coefficients for the reaction of Cl atoms with CH3Cl (k1), CH2Cl2 (k2), and CHCl3 (k3) have been determined over the temperature range 222-298 K using standard relative rate techniques. These data, when combined with evaluated data from previous studies, lead to the following Arrhenius expressions (all in units of cm3 molecule-1 s-1): k1 = (2.8±0.3)×10-11 exp(-1200±150/T); k2 = (1.5±0.2)×10-11 exp(-1100±150/T); k3 = (0.48±0.05)×10-11 exp(-1050±150/T). Values for k1 are in substantial agreement with previous measurements. However, while the room temperature values for k2 and k3 agree with most previous data, the activation energies for these rate coefficients are substantially lower than previously recommended values. In addition, the mechanism of the oxidation of CH2Cl2 has been studied. The dominant fate of the CHCl2O radical is decomposition via Cl-atom elimination, even at the lowest temperatures studied in this work (218 K). However, a small fraction of the CHCl2O radicals are shown to react with O2 at low temperatures. Using an estimated value for the rate coefficient of the reaction of CHCl2O with O2 (1×10-14 cm3 molecule-1 s-1), the decomposition rate coefficient for CHCl2O is found to be about 4×106 s-1 at 218 K, with the barrier to its decomposition estimated at 6 kcal/mole. As part of this work, the rate coefficient for Cl atoms with HCOCl was also been determined, k7 = 1.4×10-11 exp(-885/T) cm3 molecule-1 s-1, in agreement with previous determinations.
Reactivity of the radical anion OCC-
Van Doren, Jane M.,Miller, Thomas M.,Stevens Miller, Amy E.,Viggiano,Morris, Robert A.,Paulson, John F.
, p. 7407 - 7414 (2007/10/02)
The characteristic reactivity of the radical anion OCC- has been investigated in the gas phase at 298 K through determination of rate coefficients, products, and branching fractions for each of 29 ion-molecule reactions. A wide variety of reactions is observed including abstraction of H, H+, and H2+, nucleophilic displacement, charge transfer, and reactions involving electron detachment. Many of the reactions involve cleavage of the C--CO bond, consistent with the relatively small C--CO bond energy and the proposed1 electronic structure of the ground state anion in which both radical and charge are centered on the terminal carbon. Similarities are noted between the chemistry of OCC- and its neutral analogue OCC and between the chemistry of OCC- and the radical anions O- and o-C6H4-. Most reaction products observed are consistent with reaction mechanisms involving initial attack of the terminal carbon in OCC- on the neutral reaction partner. The gas-phase acidity of HCCO is bracketed between those of CH3NO2 and CH3CHO, yielding 1502 ± 8 > ΔGoacid(HCCO) ≥ 1463 ± 8 kJ mol-1 and 1531 ± 12 > ΔHoacid(HCCO) ≥ 1491 ± 12 kJ mol-1. Observation of H atom transfer from CH2Cl2 to OCC- indicates that ΔHof(OCC-) ≥ 148 ± 12 kJ mol-1 and gives a larger lower limit of ΔHoacid ≥ 1507 ± 15 kJ mol-1. These and related thermochemical values, including the hydrogen bond dissociation energy in HCCO, are compared with literature values.
Reactions of the Benzyne Radical Anion in the Gas Phase, the Acidity of the Phenyl Radical, and the Heat of Formation of o-Benzyne
Guo, Yili,Grabowski, Joseph J.
, p. 5923 - 5931 (2007/10/02)
The thermally equilibrated ion-molecule reactions of the o-benzyne radical anion have been examined in the gas phase with the flowing afterglow technique.By using the bracketing technique between o-C6H4.- and Broensted acids of known acidity, we have established the gas-phase acidity of the phenyl radical as ΔG degacid.> = 371-3+6 kcal mol-1.Combination of our experimental acidity of the phenyl radical with appropriate thermochemical data from the literature yields a variety of substantially improved thermochemical values of C6H4 and C6H5. species, most notably, ΔHfdeg = 105 kcal mol-1.In addition to behaving as a Broensted base, o-benzyne radical anion is found to undergo a number of other reactions, including electron transfer, H/D exchange, H2+ transfer, and direct addition.The reaction between o-C6H4.- and the simple aliphatic alcohols is shown to be a competition between proton transfer and H2+ transfer while that between o-C6H4.- and dioxygen or 1,3-butadiene is found to be exclusively an associative detachment process.One unanticipated, novel observation from these studies is the facile formation of an addition complex between the o-benzyne radical anion and carbon dioxide, leading to a distonic radical anion (benzoate-type anion, phenyl-type radical) that offers a unique opportunity for examining radical chemistry in ion-molecule encounter complexes.
Reaction of OH radicals with 1,1-di-, tri- and tetrachloroethylene
Kirchner,Helf,Ott,Vogt
, p. 77 - 83 (2007/10/02)
The kinetics and product formation of the homogeneous gas-phase reactions of the OH radical with 1,1-di-, tri- and tetrachloroethylene were investigated at temperatures between 298-459 K, in the pressure range of 0.5-5.6 mbar. Measurements were made in a discharge-flow apparatus, using helium as the carrier gas. The OH radical and the reaction products were detected by mass spectrometry. The rate constants were observed to be pressure independent in the case of 1,1-di- and tetrachloroethylene but slightly pressure dependent in the case of trichloroethylene. The temperature dependencies are expressed by Arrhenius equation. The major products are: CH2OH-CCl2 for 1,1-dichloroethylene; 2,2-dichloroethenol and Cl for trichloroethylene; trichloroethenol, dichloracetyl chloride, Cl, CHCl2 and phosgene for tetrachloroethylene.
Kinetics of C2F5 Radical Reactions with HCCl3 and DCCl3 in tha Gas Phase
Drys, Andrzej,Ratajczak, Emil
, p. 569 - 575 (2007/10/02)
The kinetics of pentafluoroethyl radical reactions with trichloromethane and d-trichloromethane have been studied in the static system using perfluoropropionic anhydride as a photolytic source of C2F5 radicals.The Arrhenius parameters for C2F5 radical reactions with HCCl3 and DCCl3 , based on log A 3 mol-1 s-1> = 13.40 and E=0 for the recombination reaction of C3F5 radicals, are: .The magnitude of the primary kinetic isotope effect, i.e. kH/kD=6.7 +/-4.3 at 400 K is shown to be slightly larger than might be expected on the basis of standard zero-point energy model.
