3315-37-5Relevant academic research and scientific papers
Detection of1CH2 radicals in hydrocarbon pyrolysis behind shock waves using FM spectroscopy
Deppe, Joachim,Wagner, Heinz Gg.
, p. 1501 - 1525 (2007/10/03)
Singlet methylene radical (1CH2) concentrations were measured for the first time in the pyrolysis of methane (CH4) and ethane (C2H6) behind shock waves. The very sensitive frequency modulation (FM) spectroscopy, already established for sensitve detection of amino radicals (NH2)[1,2], was used for that purpose. Applying computer simulations using a complex reaction mechanism the experimental 1CH2 signals were fitted and rate coefficients of different reaction channels were obtained. For the reaction channel (1a) CH4 + M → CH3 + H + M an extented Arrhenius expression of k1a = 6.5·1018-(T/298)-1.70·exp[-366kJ mol-1/RT] cm3mol-1s-1(±50%), and futhermore rate coefficients for (7) 3CH2+CH3 → H+C2H4 with k7 = 3.2 · 1013cm3mol-1 s-1 (±40%), (11) 3CH2 + H → CH + H2 with ku = 7.9 · 1013 cm3 mol-1 s-1 (±40%), and for the intersystem crossing via (6)1CH2+M → 3CH2+M with k6 = 1.40 · 1010 · (T/K)0.9cm3mol-1s-1 (±40%) were determined. The experimental conditions ranged from 1900 to 4000 K with corresponding pressures between 0.23 to 0.54 bar. by Oldenbourg Wissenschaftsverlag, Muenchen.
Reactions of Hyperthermal C(3P) Generated by Laser Ablation with H2, HCl, HBr, and CH3OH
Scholefield, M. R.,Goyal, S.,Choi, J.-H.,Reisler, H.
, p. 14605 - 14613 (2007/10/02)
The reactions of C(3P) with H2, HCl, HBr, and CH3OH(D) were investigated in a crossed-beam configuration using laser ablation of graphite as the source of C(3P).Upon pulsed irradiation of graphite with focused laser output at 266 and 355 nm, hyperthermal C(3P) is produced and expands freely into the vacuum.In this free ablation mode, directional beams of monomeric carbon are produced with a peak velocity of ca. 8000 m s-1 and a broad velocity distribution that can be described by temperatures of ca. 21000 and ca. 9500 K when using 266 and 355 nm ablation wavelengths, respectively.Using 266 nm ablation, the endothermic reactions of C(3P) with the title molecules were investigated by probing the CH product.CH is produced predominantly in ν = 0 with rotational distributions that are well described by temperatures in the range 1500-2200 K, depending on the molecular reactants.The spin-orbit and Λ-doublet sublevels are equally populated.In reactions with CH3OD, both CH and CD are detected, identifying both the methyl and the hydroxyl groups as reactive sites.Comparisons with the CH internal energy distributions obtained in the reaction of C(1D) with H2 show remarkable similarities.On the basis of theoretical investigations and the known electronic states of the methylene intermediate, it is suggested that the reactions of both C(3P) and C(1D) proceed via insertion involving carbene intermediates.The participation of several low-lying states of the carbenes may lead both to lowering of the activation barrier for insertion and to CH products with similar populations of the two Λ-doublet components.
Diffuse Reflectance Infrared Fourier-transform Study of the Plasma Hydrogenation of Diamond Surfaces
Ando, Toshihiro,Ishii, Motohiko,Kamo, Mutsukazu,Sato, Yoichiro
, p. 1383 - 1386 (2007/10/02)
Plasma hydrogenation of diamond surfaces was investigated using a diffuse reflectance infrared Fourier-transform (DRIFT) technique.Hydrogenation was carried out under microwave plasma conditions similar to those used for the chemical vapour deposition of diamond.Surface species chemisorbed on the diamond surface were characterized by DRIFT spectroscopy.The number of hydrogen-carbon bonds increased and the structure of the chemisorbed species on the diamond surfaces changed on increasing the temperature of the plasma hydrogenation.
Gas-Phase Atom-Radical Kinetics of Atomic Hydrogen, Nitrogen, and Oxygen Reactions with CHF Radicals.
Tsai, Cheng-ping,McFadden, David L.
, p. 3298 - 3300 (2007/10/02)
The absolute rate constants for the reactions of atomic hydrogen, nitrogen and oxygen with CHF radicals have been measured in a gas-flow system with photoionization mass spectrometry detection.CHF(1A') radicals were produced by dissociation of CH2F2, CH2FCl, or CHFBr2 in a radiofrequency discharge.CHFBr2 proved unsatisfactory as a precursor for CHF in kinetics studies.Atomic reactants were produced by dissociation of the corresponding elemental gas in a microwave discharge.The pressure was 1.7 Torr.The rate constants for CHF decay under pseudo-first-order conditions at 293 K in units of cm3 molecule-1 s-1 are (4.9 +/- 0.9) * 10-10 for CHF + H, (2.4 +/- 0.4) * 10-11 for CHF + N, and (1.4 +/- 0.2) * 10-10 for CHF + O.These reactions appear to proceed by an association-elimination mechanism.
Computed high-temperature rate constants for hydrogen-atom transfers involving light atoms
Mayer,Schieler,Johnston, Harold S.
, p. 385 - 391 (2008/10/08)
The procedure of Johnston and Parr for computing the potential energy and structure of a triatomic linear activated complex containing hydrogen as its central atom has been combined with the EyringPolanyi rate-constant expression to calculate rate constants at 1000° to 4000°K of gas-phase hydrogen-atom transfers for every possible reaction between the ground states of the atoms H, Li, Be, B, C, N, O, F, Na, Cl, Br, I, and any of the diatomic hydrogen compounds of these elements. The relation between activated complex theory and collision theory for reactions of this sort is examined in detail. The usual form of activated complex theory breaks down for reactions of low activation energy and high temperature, and the conditions for this failure in terms of bending vibrational amplitude are given. For these cases rate constants are evaluated by hard-sphere collision theory. Although calculated activation energy and other parameters differ from one reaction to another, these differences become unimportant at very high temperature. Almost all calculated rate constants have a value within a factor of 4 of the single value 2X10 13cc/mole/sec at 2500°K.
