Time- and Isomer-Resolved Measurements of Sequential Addition of Acetylene to the Propargyl Radical

Savee, John David; Selby, Talitha M.; Welz, Oliver; Taatjes, Craig A.; Osborn, David L.

doi:10.1021/acs.jpclett.5b01896

Cited by 39 publications

(58 citation statements)

References 28 publications

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“…6(d)], several changes were made to the mechanism: We included the cyclization reactions of the benzyl radical with 1,3-butadiene and the 1,3-butadiene-1-yl radical (n-C 4 H 5 ) as proposed by Fascella et al [34] and the addition reaction of methyl to phenylacetylene (A1C2H) using a rate for a similar reaction from Marinov et al [27]. Furthermore, an indene formation pathway via cycloheptatriene suggested by Savee et al [35] was added but found not to contribute.…”

Section: Resultsmentioning

confidence: 99%

Aromatic ring formation in opposed-flow diffusive 1,3-butadiene flames

Moshammer

Seidel

Wang

et al. 2017

Proceedings of the Combustion Institute

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This paper is concerned with the formation of one-and two-ring aromatic species in near atmospheric-pressure opposed-flow diffusion flames of 1,3-butadiene (1,3-C 4 H 6). The chemical structures of two different 1,3-C 4 H 6 /Ar-O 2 /Ar flames were explored using flame-sampling molecular-beam mass spectrometry with both electron and single-photon ionization. We provide mole fraction profiles of 47 components as function of distance from the fuel outlet and compare them to chemically detailed modeling results. To this end, the hierarchically developed model described by Seidel et al. [Combust. Flame 162 (2015) 2045-2058] has been updated to accurately comprise the chemistry of 1,3-butadiene. Generally a very good agreement is observed between the experimental and modeling data, allowing for a meaningful reaction path analysis. With regard to the formation of aromatic species up to naphthalene, it was essential to improve the fulvene and the C 5 chemistry description in the mechanism. In particular, benzene is found to be formed mainly via fulvene through the reactions of the C 4 H 5 isomers with C 2 H 2. The n-C 4 H 5 radical reacts with CH 3 forming 1,3-pentadiene (C 5 H 8), which is 3 subsequently oxidized to form the naphthalene precursor cyclopentadienyl (C 5 H 5). Oxidation of naphthalene is predicted to be a contributor to the formation of phenylacetylene (C 8 H 6), indicating that consumption reactions can be of similar importance as molecular growth reactions.

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Section: Resultsmentioning

confidence: 99%

Aromatic ring formation in opposed-flow diffusive 1,3-butadiene flames

Moshammer

Seidel

Wang

et al. 2017

Proceedings of the Combustion Institute

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“…These findings are consistent with the failure 7 of tunable PIMS to detect C 7 H 7 radicals as benzyl undergoes pyrolysis. Very recently, time-resolved PIMS spectroscopy was used 47 to study soot formation. The addition of acetylene to propargyl radical in a slow flow quartz reactor at (10 Torr/1000 K) was found to induce molecular weight growth via the sequence: HC≡≡CH + HCCCH 2 → C 5 H 5 → C 7 H 7 .…”

Section: Discussionmentioning

confidence: 99%

The thermal decomposition of the benzyl radical in a heated micro-reactor. II. Pyrolysis of the tropyl radical

Buckingham

Porterfield

Kostko

et al. 2016

The Journal of Chemical Physics

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Cycloheptatrienyl (tropyl) radical, C7H7, was cleanly produced in the gas-phase, entrained in He or Ne carrier gas, and subjected to a set of flash-pyrolysis micro-reactors. The pyrolysis products resulting from C7H7 were detected and identified by vacuum ultraviolet photoionization mass spectrometry. Complementary product identification was provided by infrared absorption spectroscopy. Pyrolysis pressures in the micro-reactor were roughly 200 Torr and residence times were approximately 100 μs. Thermal cracking of tropyl radical begins at 1100 K and the products from pyrolysis of C7H7 are only acetylene and cyclopentadienyl radicals. Tropyl radicals do not isomerize to benzyl radicals at reactor temperatures up to 1600 K. Heating samples of either cycloheptatriene or norbornadiene never produced tropyl (C7H7) radicals but rather only benzyl (C6H5CH2). The thermal decomposition of benzyl radicals has been reconsidered without participation of tropyl radicals. There are at least three distinct pathways for pyrolysis of benzyl radical: the Benson fragmentation, the methyl-phenyl radical, and the bridgehead norbornadienyl radical. These three pathways account for the majority of the products detected following pyrolysis of all of the isotopomers: C6H5CH2, C6H5CD2, C6D5CH2, and C6H5 (13)CH2. Analysis of the temperature dependence for the pyrolysis of the isotopic species (C6H5CD2, C6D5CH2, and C6H5 (13)CH2) suggests the Benson fragmentation and the norbornadienyl pathways open at reactor temperatures of 1300 K while the methyl-phenyl radical channel becomes active at slightly higher temperatures (1500 K).

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“…48 Trace amounts of l-C 5 H 5 also contribute to the threshold ion signal between 8.0 and 8.2 eV, and their involvement in the reaction pathways might also be noticeable in light of recent findings. 47,49 A mechanism for the formation of l-C 5 H 5 and the PIE curve showing some evidence is displayed in the ESI † ( Fig. S3 and S4).…”

Section: Mass Spectrometric Analysismentioning

confidence: 99%

Are the three hydroxyphenyl radical isomers created equal? – The role of the phenoxy radical –

Hemberger

Silva

Trevitt

et al. 2015

Phys. Chem. Chem. Phys.

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We have investigated the thermal decomposition of the three hydroxyphenyl radicals (˙C6H4OH) in a heated microtubular reactor. Intermediates and products were identified isomer-selectively applying photoion mass-selected threshold photoelectron spectroscopy with vacuum ultraviolet synchrotron radiation. Similarly to the phenoxy radical (C6H5-O˙), hydroxyphenyl decomposition yields cyclopentadienyl (c-C5H5) radicals in a decarbonylation reaction at elevated temperatures. This finding suggests that all hydroxyphenyl isomers first rearrange to form phenoxy species, which subsequently decarbonylate, a mechanism which we also investigate computationally. Meta- and para-radicals were selectively produced and spectroscopically detectable, whereas the ortho isomer could not be traced due to its fast rethermalization and rapid decomposition in the reactor. A smaller barrier to isomerization to phenoxy was found to be the reason for this observation. Since hydroxyphenyl species may be present under typical sooting conditions in flames, the resonantly stabilized cyclopentadienyl radical adds to the hydrocarbon pool and can contribute to the formation of polycyclic aromatic hydrocarbons, which are precursors in soot formation.

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Time- and Isomer-Resolved Measurements of Sequential Addition of Acetylene to the Propargyl Radical

Cited by 39 publications

References 28 publications

Aromatic ring formation in opposed-flow diffusive 1,3-butadiene flames

Aromatic ring formation in opposed-flow diffusive 1,3-butadiene flames

The thermal decomposition of the benzyl radical in a heated micro-reactor. II. Pyrolysis of the tropyl radical

Are the three hydroxyphenyl radical isomers created equal? – The role of the phenoxy radical –

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