Gas-phase synthesis of benzene via the propargyl radical self-reaction

Zhao, Long; Lu, Wenchao; Ahmed, Musahid; Загидуллин, М. В.; Azyazov, Valeriy N.; Morozov, Alexander N.; Mebel, Alexander M.; Kaiser, Ralf I.

doi:10.1126/sciadv.abf0360

Cited by 44 publications

(59 citation statements)

References 99 publications

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“…In a side pathway, propene can also react with methyl radical and dehydrogenate to produce butene (C 4 H 8 , m/z 56) The propargyl radical is a key species that can react with (i) C 1 species to produce 1,3-butadiene, (ii) acetylene to produce cyclopentadienyl, or (iii) with another propargyl to produce the benzene (11) and fulvene (15). [6] The tunability of the VUV photon energy in iPEPICO allows us to confirm the formation of both C 6 H 6 isomers based on their IE (9.24 eV for benzene and 8.36 eV for fulvene). [7] The formation of C 3 species (CC 3 H 3 , CC 3 H 5 , CC 3 H 7 , C 3 H 4 , C 3 H 6 , and C 3 H 8 ) as well as C 4 H 6 are plausible mass growth pathways in methane conversion under non-oxidative conditions.…”

Section: Methodsmentioning

confidence: 86%

Direct Evidence on the Mechanism of Methane Conversion under Non‐oxidative Conditions over Iron‐modified Silica: The Role of Propargyl Radicals Unveiled

et al. 2021

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Radical‐mediated gas‐phase reactions play an important role in the conversion of methane under non‐oxidative conditions into olefins and aromatics over iron‐modified silica catalysts. Herein, we use operando photoelectron photoion coincidence spectroscopy to disentangle the elusive C2+ radical intermediates participating in the complex gas‐phase reaction network. Our experiments pinpoint different C2‐C5 radical species that allow for a stepwise growth of the hydrocarbon chains. Propargyl radicals (H2C−C≡C−H) are identified as essential precursors for the formation of aromatics, which then contribute to the formation of heavier hydrocarbon products via hydrogen abstraction–acetylene addition routes (HACA mechanism). These results provide comprehensive mechanistic insights that are relevant for the development of methane valorization processes.

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Section: Methodsmentioning

confidence: 86%

Direct Evidence on the Mechanism of Methane Conversion under Non‐oxidative Conditions over Iron‐modified Silica: The Role of Propargyl Radicals Unveiled

et al. 2021

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“…Being that abundant, the propargyl radical could very well play an important role in the synthesis of aromatic molecules. For example, calculations indicate that the propargyl radical selfreaction can lead to cyclization, producing the aromatic radical phenyl radical at low temperatures (Miller & Klippenstein 2001;Zhao et al 2021).…”

Section: Introductionmentioning

confidence: 99%

Detection of the propargyl radical at λ 3 mm

Agúndez

Marcelino

Cabezas

et al. 2022

A&A

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We report the detection of the propargyl radical (CH2CCH) in the cold dark cloud TMC-1 in the λ 3 mm wavelength band. We recently discovered this species in space toward the same source at a wavelength of λ 8 mm. In those observations, various hyperfine components of the 20,2–10,1 rotational transition, at 37.5 GHz, were detected using the Yebes 40 m telescope. Here, we used the IRAM 30 m telescope to detect ten hyperfine components of the 50,5–40,4 rotational transition, lying at 93.6 GHz. The observed frequencies differ by 0.2 MHz with respect to the predictions from available laboratory data. This difference is significant for a radio-astronomical search for CH2CCH in interstellar sources with narrow lines. We thus included the measured frequencies in a new spectroscopic analysis to provide accurate frequency predictions for the interstellar search for propargyl at millimeter wavelengths. Moreover, we recommend that future searches for CH2CCH in cold interstellar clouds be carried out at λ 3 mm rather than at λ 8 mm. The 50,5–40,4 transition is about five times more intense than the 20,2–10,1 one in TMC-1, which implies that detecting the former requires about seven times less telescope time than detecting the latter. We constrain the rotational temperature of CH2CCH in TMC-1 to 9.9 ± 1.5 K, which indicates that the rotational levels of this species are thermalized at the gas kinetic temperature. The revised value of the column density of CH2CCH (including ortho and para species) is (1.0 ± 0.2) × 1014 cm−2, and thus the CH2CCH/CH3CCH abundance ratio is revised slightly higher, approaching one. This study opens the door to future detections of CH2CCH in other cold interstellar clouds, making it possible to further investigate the role of this very abundant hydrocarbon radical in the synthesis of large organic molecules, such as aromatic rings.

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“…Recently, Zhao et al showed that molecular growth processes can occur via the reaction between two stabilized propargyl radicals at high temperature and diluted environments. Such a reaction can lead to the formation of benzene molecules, among other species [ 26 ].…”

Section: Introductionmentioning

confidence: 99%

The Effect of Cluster Size on the Intra-Cluster Ionic Polymerization Process

Molina

Stein

2021

Molecules

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Polyaromatic hydrocarbons (PAHs) are widespread in the interstellar medium (ISM). The abundance and relevance of PAHs call for a clear understanding of their formation mechanisms, which, to date, have not been completely deciphered. Of particular interest is the formation of benzene, the basic building block of PAHs. It has been shown that the ionization of neutral clusters can lead to an intra-cluster ionic polymerization process that results in molecular growth. Ab-initio molecular dynamics (AIMD) studies in clusters consisting of 3–6 units of acetylene modeling ionization events under ISM conditions have shown maximum aggregation of three acetylene molecules forming bonded C6H6+ species; the larger the number of acetylene molecules, the higher the production of C6H6+. These results lead to the question of whether clusters larger than those studied thus far promote aggregation beyond three acetylene units and whether larger clusters can result in higher C6H6+ production. In this study, we report results from AIMD simulations modeling the ionization of 10 and 20 acetylene clusters. The simulations show aggregation of up to four acetylene units producing bonded C8H8+. Interestingly, C8H8+ bicyclic species were identified, setting a precedent for their astrochemical identification. Comparable reactivity rates were shown with 10 and 20 acetylene clusters.

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Gas-phase synthesis of benzene via the propargyl radical self-reaction

Cited by 44 publications

References 99 publications

Direct Evidence on the Mechanism of Methane Conversion under Non‐oxidative Conditions over Iron‐modified Silica: The Role of Propargyl Radicals Unveiled

Direct Evidence on the Mechanism of Methane Conversion under Non‐oxidative Conditions over Iron‐modified Silica: The Role of Propargyl Radicals Unveiled

Detection of the propargyl radical at λ 3 mm

The Effect of Cluster Size on the Intra-Cluster Ionic Polymerization Process

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