Reactions of the ethynyl radical. Part 1.—Hydrogen abstraction from alkanes

Tarr, A. M.; Strausz, O. P.; Gunning, H. E.

doi:10.1039/tf9656101946

Cited by 28 publications

(22 citation statements)

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“…In a C 2 H + CH 3 CN f C 2 H 2 + CH 2 CN ∆H rxn ) -180 kJ/mol C 2 H + CH 3 CN f HCCCN + CH 3 ∆H rxn ) -150 kJ/mol related study, it was found that the rate constant for the C 2 H reaction with C 2 H 5 Cl is approximately 6 times smaller than the rate constant for the C 2 H reaction with C 2 H 5 Br, in agreement with an expectation based on the relative electronegativities of the Cl and Br atoms. 39 Unfortunately, in this earlier study of the C 2 H reactions with alkanes only the relative rate constants were measured, 39 and a comparison of the rate constants for the C 2 H reactions with C 2 H 5 CN, C 2 H 5 Cl, and C 2 H 5 Br is not possible. The photochemical models of Titan's atmosphere include CH 3 CN, but they limit the loss processes of the species to photolysis and condensation.…”

Section: Resultsmentioning

confidence: 99%

Kinetics of C₂H Reactions with Hydrocarbons and Nitriles in the 104−296 K Temperature Range

Nizamov

Leone

2004

J. Phys. Chem. A

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Reactions of C 2 H with isobutane (k 1 ), 1-butene (k 2 ), isobutylene (k 3 ), 1,3-butadiene (k 4 ), methyl cyanide (k 5 ), ethyl cyanide (k 6 ), and propyl cyanide (k 7 ) are studied at low temperature using a pulsed Laval nozzle apparatus. The C 2 H radical is prepared by 193-nm photolysis of acetylene, and the C 2 H concentration is monitored using CH(A 2 ∆) chemiluminescence from the C 2 H + O 2 reaction. The rate constants at low and high temperatures are k 1 ) (1.3 ( 0.3) × 10 -10 and (1.0 ( 0.2) × 10 -10 for isobutane, k 2 ) (2.1 ( 0.4) × 10 -10 and (2.2 ( 0.4) × 10 -10 for 1-butene, k 3 ) (1.4 ( 0.3) × 10 -10 and (1.2 ( 0.2) × 10 -10 for isobutylene, and k 4 ) (2.9 ( 0.6) × 10 -10 and (3.3 ( 0.6) × 10 -10 for 1,3-butadiene at T ) 104 and 296 K, respectively (in units of cm 3 molecule -1 s -1 ). Comparison with existing data shows a trend of a decrease in activation energy with increasing size of the hydrocarbon chain. For these reactions of hydrocarbons containing four carbon atoms, the activation energy is zero within experimental uncertainty, and the rate constants do not depend on temperature in the 104-296 K temperature range. The rate constants for C 2 H reactions with methyl cyanide, ethyl cyanide, and propyl cyanide are measured at three temperatures, 104, 165, and 298 K. Measured rate constants are fit to an Arrhenius expression and are k 5 ) (1.8 ( 0.35) × 10 -11 exp(-766 ( 38/T), k 6 ) (1.5 ( 0.3) × 10 -11 exp(-145 ( 10/T), and k 7 ) (2.1 ( 0.4) × 10 -11 exp(-51 ( 4/T) (in units of cm 3 molecule -1 s -1 , T is in Kelvin). At T ) 296 K, k 3 , k 5 , k 6 , and k 7 are measured as a function of total pressure and show no pressure dependence in the 0.6-8 Torr (0.08-1.07 kPa) pressure range. Results from this work are compared with the results of previous investigations of C 2 H reactions at low temperature and are discussed in relation to the atmospheres of Saturn and Titan.

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Section: Resultsmentioning

confidence: 99%

Kinetics of C₂H Reactions with Hydrocarbons and Nitriles in the 104−296 K Temperature Range

Nizamov

Leone

2004

J. Phys. Chem. A

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“…Both of these conditions lead to <IA' lalaOlA"> tan7-(2A' ta/aOlA"> " (6) In contrast to (4) the determination of the transformation angle 7 by means of (5) and (6) does not require any additional calculations other than those serving to generate the potential energy surfaces and the elementary properties (the transition moments and the matrix elements of the electronic angular momentum).…”

Section: Iii) the Z Component Of The Electronic Angular Momentum L= Imentioning

confidence: 97%

Analysis and predictions of the vibronic spectrum of the ethynyl radical C2H by ab initio methods

Perić

Peyerimhoff

Buenker

1992

Z Phys D - Atoms, Molecules and Clusters

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Abstract.A purely ab initio study of the vibronic structure of the C2 H spectrum in the region up to 7000 cm -~, which is complicated by the coupling of the X 2 Z + and A 2H systems, is presented. The potential surfaces for the three lowest-lying electronic states 12A', 22A ' and 12A" correlating with X 2L" + and A 2H at the linear molecular geometry are calculated for the various geometrical distortions by means of the multireference configuration interaction (MRD-CI) method. These adiabatic surfaces are transformed into suitable diabatic counterparts. An approach is developed for a simultaneous treatment of three electronic states coupled via the bending and C-C stretching vibrations. Spin-orbit splitting of the vibronic levels and the vibronically averaged values for the hyperfine coupling constants are computed. The results obtained in this study enable a reliable explanation of the available experimental findings of the C2 H spectrum and predict a number of features to be verified by future experiments.

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“…Fangtong et al employed 193 nm BrC 2 H photodissociation in a crossed-molecular beams experiment and indicated that approximately 6% of the BrC 2 H is decomposed into Br + C 2 H with a laser fluence of $400 mJ cm À2 [41]. The absorption of 248 nm light by BrC 2 H is reported to be around 30 times lower than that of 200 nm light [42]. Due to the absence of absorption data at 193 nm, the assumption is made that the absorption at 193 nm is similar to 200 nm.…”

Section: Multiplexed Photoionization Mass Spectrometermentioning

confidence: 98%

Formation of fulvene in the reaction of C2H with 1,3-butadiene

Lockyear

Fournier

Sims

et al. 2015

International Journal of Mass Spectrometry

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A B S T R A C TProducts formed in the reaction of C 2 H radicals with 1,3-butadiene at 4 Torr and 298 K are probed using photoionization time-of-flight mass spectrometry. The reaction takes place in a slow-flow reactor, and products are ionized by tunable vacuum-ultraviolet light from the Advanced Light Source. The principal reaction channel involves addition of the radical to one of the unsaturated sites of 1,3-butadiene, followed by H-loss to give isomers of C 6 H 6 . The photoionization spectrum of the C 6 H 6 product indicates that fulvene is formed with a branching fraction of (57 AE 30)%. At least one more isomer is formed, which is likely to be one or more of 3,4-dimethylenecyclobut-1-ene, 3-methylene-1-penten-4-yne or 3-methyl-1,2-pentadien-4-yne. An experimental photoionization spectrum of 3,4-dimethylenecyclobut-1-ene and simulated photoionization spectra of 3-methylene-1-penten-4-yne and 3-methyl-1,2-pentadien-4-yne are used to fit the measured data and obtain maximum branching fractions of 74%, 24% and 31%, respectively, for these isomers. An upper limit of 45% is placed on the branching fraction for the sum of benzene and 1,3-hexadien-5-yne. The reactive potential energy surface is also investigated computationally. Minima and first-order saddle-points on several possible reaction pathways to fulvene + H and 3,4-dimethylenecyclobut-1-ene + H products are calculated.Published by Elsevier B.V.

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Reactions of the ethynyl radical. Part 1.—Hydrogen abstraction from alkanes

Cited by 28 publications

References 2 publications

Kinetics of C₂H Reactions with Hydrocarbons and Nitriles in the 104−296 K Temperature Range

Kinetics of C₂H Reactions with Hydrocarbons and Nitriles in the 104−296 K Temperature Range

Analysis and predictions of the vibronic spectrum of the ethynyl radical C2H by ab initio methods

Formation of fulvene in the reaction of C2H with 1,3-butadiene

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Reactions of the ethynyl radical. Part 1.—Hydrogen abstraction from alkanes

Cited by 28 publications

References 2 publications

Kinetics of C2H Reactions with Hydrocarbons and Nitriles in the 104−296 K Temperature Range

Kinetics of C2H Reactions with Hydrocarbons and Nitriles in the 104−296 K Temperature Range

Analysis and predictions of the vibronic spectrum of the ethynyl radical C2H by ab initio methods

Formation of fulvene in the reaction of C2H with 1,3-butadiene

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Kinetics of C₂H Reactions with Hydrocarbons and Nitriles in the 104−296 K Temperature Range

Kinetics of C₂H Reactions with Hydrocarbons and Nitriles in the 104−296 K Temperature Range