Identification of C5Hx Isomers in Fuel-Rich Flames by Photoionization Mass Spectrometry and Electronic Structure Calculations

Hansen, Nils; Klippenstein, Stephen J.; Miller, James A.; Wang, Juan; Cool, Terrill A.; Law, Matthew E.; Westmoreland, Phillip R.; Kasper, Tina; Kohse‐Höinghaus, Katharina

doi:10.1021/jp0569685

Cited by 130 publications

(179 citation statements)

References 59 publications

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“…The solid black line in Figure 7(a) indicates the fit including only the contribution of the CH 2 CCHCCH isomer. Note that the calculated photoionization efficiency curve increases slowly above 9.25 eV with a step around 9.5 eV, 62 almost coinciding with the next threshold in the ion signal. However, the fit assuming only ethynylallene contributes to the PIE curve between 8.1 and 9.9 eV is fairly poor, which suggests the presence of an additional isomer.…”

Section: Photodissociation and Photoproducts Of Reactants At 193 Nmsupporting

confidence: 52%

“…The PIE curve is normalized to the total estimated cross section of an average mixture of 18% of fulvene, 32% of DMCB, 8% of 2-ethynyl-1,3-butadiene, 28% of 3,4-hexadiene-1-yne and 14% of 1,3-hexadiyne using the estimated photoionization cross sections at 10 eV reported in Table 6. 62 cannot be probed. The signal is normalized to the total estimated photoionization cross section at 9.8 eV using estimated values reported in Table 5.…”

Section: Resultsmentioning

confidence: 99%

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Reaction of the C₂H Radical with 1-Butyne (C₄H₆): Low-Temperature Kinetics and Isomer-Specific Product Detection

Soorkia

Trevitt

Selby³

et al. 2010

J. Phys. Chem. A

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The rate coefficient for the reaction of the ethynyl radical (C 2 H) with 1-butyne (H-C≡C-CH 2 -CH 3 ) is measured in a pulsed Laval nozzle apparatus. Ethynyl radicals are formed by laser photolysis of acetylene (C 2 H 2 ) at 193 nm and detected via chemiluminescence (C 2 H + O 2 → CH (A 2 Δ) + CO 2 ). The rate coefficients are measured over the temperature range of 74-295 K. The C 2 H + 1-butyne reaction exhibits no barrier and occurs with rate constants close to the collision limit. The temperature dependent rate coefficients can be fit within experimental uncertainties by the expression k = (2.4 ± 0.5) × 10 -10 (T/295 K) -(0.04 ± 0.03) cm 3 molecule -1 s -1 . Reaction products are detected at room temperature (295 K) and 533 Pa using a Multiplexed Photoionization Mass Spectrometer (MPIMS) coupled to the tunable VUV synchrotron radiation from the Advanced Light Source at the Lawrence Berkeley National Laboratory. Two product channels are identified for this reaction: m/z = 64 (C 5 H 4 ) and m/z = 78 (C 6 H 6 ) corresponding to the CH 3 -and H-loss channels, respectively. Photoionization efficiency (PIE) curves are used to analyze the isomeric composition of both product channels. The C 5 H 4 products are found to be exclusively linear isomers composed of ethynylallene and methyldiacetylene in a 4:1 ratio. In contrast, the C 6 H 6 product channel includes two cyclic isomers, fulvene 18(±5)% and 3,4-dimethylenecyclobut-1-ene 32(±8)%, as well as three linear isomers, 2-ethynyl-1,3-butadiene 8(±5)%, 3,4-hexadiene-1-yne 28(±8)% and 1,3-hexadiyne 14(±5)%. Within experimental uncertainties, we do not see appreciable amounts of benzene and an upper limit of 10 % is estimated. Diacetylene (C 4 H 2 ) formation via the C 2 H 5 -loss channel is also thermodynamically possible but cannot be observed due to experimental limitations. The implications of these results for modeling of planetary atmospheres, especially of Saturn's largest moon Titan, are discussed.

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Section: Photodissociation and Photoproducts Of Reactants At 193 Nmsupporting

confidence: 52%

Section: Resultsmentioning

confidence: 99%

Reaction of the C₂H Radical with 1-Butyne (C₄H₆): Low-Temperature Kinetics and Isomer-Specific Product Detection

Soorkia

Trevitt

Selby³

et al. 2010

J. Phys. Chem. A

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“…Many calculations were refined at a higher level of theory, where QCISD(T)/CBS//M06-2X/aug-cc-pVTZ energies were approximated via QCISD(T)/aug-cc-pVTZ + MP2/CBS -MP2/aug-cc-pVTZ (all calculated at the M06-2X/aug-cc-pVTZ geometries), with the complete basis set (CBS) limit estimated using a two-point formula 72 and the aug-cc-pVTZ and aug-cc-pVQZ basis sets. This level of theory is labeled ~QCISD(T)/CBS and is very similar to one used previously, [73][74][75][76] with an estimated uncertainty of ±0.05 eV. For ionization of doublet species, both singlet and triplet cations were considered, and the adiabatic ionization energy for the lowest-energy cation is reported.…”

Section: Theorymentioning

confidence: 98%

Detection and Identification of the Keto-Hydroperoxide (HOOCH₂OCHO) and Other Intermediates during Low-Temperature Oxidation of Dimethyl Ether

et al. 2015

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In this paper we report the detection and identification of the keto-hydroperoxide (hydroperoxymethyl formate, HPMF, HOOCH 2 OCHO) and other partially oxidized intermediate species arising from the low-temperature (540 K) oxidation of dimethyl ether (DME). These observations were made possible by coupling a jet-stirred reactor with molecular-beam sampling capabilities, operated near atmospheric pressure, to a reflectron time-of-flight mass spectrometer that employs single-photon ionization via tunable synchrotron-generated vacuum-ultraviolet radiation. Based on experimentally observed ionization thresholds and fragmentation appearance energies, interpreted with the aid of ab initio calculations, we have identified HPMF and its

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“…It is also important to consider possible C 7 H 5 radical decomposition channels to acetylene plus a C 5 H 3 radical at higher temperatures. It is well accepted that the two most stable C 5 H 3 radicals are the i-C 5 H 3 (CH 2 CCCCH) and n-C 5 H 3 (CHCCHCCH) isomers, 15 and reaction pathways to these two product channels are also included in our full C 4 H 2 + C 3 H 3 potential energy surface. Furthermore, this energy surface is also used to study the kinetics of these two important C 5 H 3 radicals reacting with acetylene.…”

Section: Downloaded By University Of Wollongong On 30 November 2011mentioning

confidence: 99%

Chemically activated reactions on the C7H5 energy surface: propargyl + diacetylene, i-C5H3 + acetylene, and n-C5H3 + acetylene

Silva

Trevitt

2011

Phys. Chem. Chem. Phys.

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This study uses computational chemistry and statistical reaction rate theory to investigate the chemically activated reaction of diacetylene (butadiyne, C4H2) with the propargyl radical (C •H2CCH) and the reaction of acetylene (C 2H2) with the i-C5H3 (CH 2CCCC•H) and n-C5H3 (CHCC •HCCH) radicals. A detailed G3SX-level C7H 5 energy surface demonstrates that the C3H3 + C4H2 and C5H3 + C2H 2 addition reactions proceed with moderate barriers, on the order of 10 to 15 kcal mol-1, and form activated open-chain C 7H5 species that can isomerize to the fulvenallenyl radical with the highest barrier still significantly below the entrance channel energy. Higher-energy pathways are available leading to other C 7H5 isomers and to a number of C7H4 species + H. Rate constants in the large multiple-well (15) multiple-channel (30) chemically activated system are obtained from a stochastic solution of the one-dimensional master equation, with RRKM theory for microcanonical rate constants. The dominant products of the C4H2 + C 3H3 reaction at combustion-relevant temperatures and pressures are i-C5H3 + C2H2 and CH2CCHCCCCH + H, along with several quenched C7H 5 intermediate species below 1500 K. The major products in the n-C5H3 + C2H2 reaction are i-C 5H3 + C2H2 and a number of C 7H4 species + H, with C7H5 radical stabilization at lower temperatures. The i-C5H3 + C 2H2 reaction predominantly leads to C7H 4 + H and to stabilized C7H5 products. The title reactions may play an important role in polycyclic aromatic hydrocarbon (PAH) formation in combustion systems. The C7H5 potential energy surface developed here also provides insight into several other important reacting gas-phase systems relevant to combustion and astrochemistry, including C2H + the C3H4 isomers propyne and allene, benzyne + CH, benzene + C(3P), and C7H5 radical decomposition, for which some preliminary analysis is presented.

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Identification of C₅H_x Isomers in Fuel-Rich Flames by Photoionization Mass Spectrometry and Electronic Structure Calculations

Cited by 130 publications

References 59 publications

Reaction of the C₂H Radical with 1-Butyne (C₄H₆): Low-Temperature Kinetics and Isomer-Specific Product Detection

Reaction of the C₂H Radical with 1-Butyne (C₄H₆): Low-Temperature Kinetics and Isomer-Specific Product Detection

Detection and Identification of the Keto-Hydroperoxide (HOOCH₂OCHO) and Other Intermediates during Low-Temperature Oxidation of Dimethyl Ether

Chemically activated reactions on the C7H5 energy surface: propargyl + diacetylene, i-C5H3 + acetylene, and n-C5H3 + acetylene

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Identification of C5Hx Isomers in Fuel-Rich Flames by Photoionization Mass Spectrometry and Electronic Structure Calculations

Cited by 130 publications

References 59 publications

Reaction of the C2H Radical with 1-Butyne (C4H6): Low-Temperature Kinetics and Isomer-Specific Product Detection

Reaction of the C2H Radical with 1-Butyne (C4H6): Low-Temperature Kinetics and Isomer-Specific Product Detection

Detection and Identification of the Keto-Hydroperoxide (HOOCH2OCHO) and Other Intermediates during Low-Temperature Oxidation of Dimethyl Ether

Chemically activated reactions on the C7H5 energy surface: propargyl + diacetylene, i-C5H3 + acetylene, and n-C5H3 + acetylene

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Identification of C₅H_x Isomers in Fuel-Rich Flames by Photoionization Mass Spectrometry and Electronic Structure Calculations

Reaction of the C₂H Radical with 1-Butyne (C₄H₆): Low-Temperature Kinetics and Isomer-Specific Product Detection

Reaction of the C₂H Radical with 1-Butyne (C₄H₆): Low-Temperature Kinetics and Isomer-Specific Product Detection

Detection and Identification of the Keto-Hydroperoxide (HOOCH₂OCHO) and Other Intermediates during Low-Temperature Oxidation of Dimethyl Ether