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Kaiser RI, Zhao L, Lu W, Ahmed M, Zagidullin MV, Azyazov VN, Mebel AM. Formation of Benzene and Naphthalene through Cyclopentadienyl-Mediated Radical-Radical Reactions. J Phys Chem Lett 2022; 13:208-213. [PMID: 34967648 DOI: 10.1021/acs.jpclett.1c03733] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Resonantly stabilized free radicals (RSFRs) have been contemplated as fundamental molecular building blocks and reactive intermediates in molecular mass growth processes leading to polycyclic aromatic hydrocarbons (PAHs) and carbonaceous nanoparticles on Earth and in deep space. By combining molecular beams and computational fluid dynamics simulations, we provide compelling evidence on the formation of benzene via the cyclopentadienyl-methyl reaction and of naphthalene through the cyclopentadienyl self-reaction, respectively. These systems offer benchmarks for the conversion of a five-membered ring to the 6π-aromatic (benzene) and the generation of the simplest 10π-PAH (naphthalene) at elevated temperatures. These results uncover molecular mass growth processes from the "bottom up" via RSFRs in high temperature circumstellar environments and combustion systems expanding our fundamental knowledge of the organic, hydrocarbon chemistry in our universe.
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Affiliation(s)
- Ralf I Kaiser
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822, United States
| | - Long Zhao
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822, United States
| | - Wenchao Lu
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Musahid Ahmed
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Marsel V Zagidullin
- Lebedev Physical Institute, Samara Branch, Samara 443011, Russian Federation
| | - Valeriy N Azyazov
- Lebedev Physical Institute, Samara Branch, Samara 443011, Russian Federation
| | - Alexander M Mebel
- Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, United States
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Caster KL, Selby TM, Osborn DL, Le Picard SD, Goulay F. Product Detection of the CH(X 2Π) Radical Reaction with Cyclopentadiene: A Novel Route to Benzene. J Phys Chem A 2021; 125:6927-6939. [PMID: 34374546 DOI: 10.1021/acs.jpca.1c03517] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The reaction of the methylidyne radical (CH(X2Π)) with cyclopentadiene (c-C5H6) is studied in the gas phase at 4 Torr and 373 K using a multiplexed photoionization mass spectrometer. Under multiple collision conditions, the dominant product channel observed is the formation of C6H6 + H. Fitting the photoionization spectrum using reference spectra allows for isomeric resolution of C6H6 isomers, where benzene is the largest contributor with a relative branching fraction of 90 (±5)%. Several other C6H6 isomers are found to have smaller contributions, including fulvene with a branching fraction of 8 (±5)%. Master Equation calculations for four different entrance channels on the C6H7 potential energy surface are performed to explore the competition between CH cycloaddition to a C═C bond vs CH insertion into C-H bonds of cyclopentadiene. Previous studies on CH addition to unsaturated hydrocarbons show little evidence for the C-H insertion pathway. The present computed branching fractions support benzene as the sole cyclic product from CH cycloaddition, whereas fulvene is the dominant product from two of the three pathways for CH insertion into the C-H bonds of cyclopentadiene. The combination of experiment with Master Equation calculations implies that insertion must account for ∼10 (±5)% of the overall CH + cyclopentadiene mechanism.
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Affiliation(s)
- Kacee L Caster
- C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, West Virginia 26506, United States
| | - Talitha M Selby
- Department of Mathematics and Natural Sciences, University of Wisconsin-Milwaukee, West Bend, Wisconsin 53095, United States
| | - David L Osborn
- Combustion Research Facility, Sandia National Laboratories, Mail Stop 9055, Livermore, California 94551, United States
| | - Sebastien D Le Picard
- IPR (Institut de Physique de Rennes), UMR 6251, Univ Rennes, CNRS, F-35000 Rennes, France
| | - Fabien Goulay
- C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, West Virginia 26506, United States
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Wong ZC, Ungur L. Deriving the vibronic coupling constants of the cyclopentadienyl radical with density functional theory and G0W0. J Chem Phys 2020; 153:064303. [DOI: 10.1063/5.0014753] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Zi Cheng Wong
- Department of Chemistry, National University of Singapore, Block S8 Level 3, 3 Science Drive 3, 117543, Singapore
| | - Liviu Ungur
- Department of Chemistry, National University of Singapore, Block S8 Level 3, 3 Science Drive 3, 117543, Singapore
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Sullivan EN, Nichols B, von Kugelgen S, da Silva G, Neumark DM. Multiphoton dissociation dynamics of the indenyl radical at 248 nm and 193 nm. J Chem Phys 2019; 151:174303. [PMID: 31703498 PMCID: PMC7043848 DOI: 10.1063/1.5121294] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Accepted: 10/10/2019] [Indexed: 11/14/2022] Open
Abstract
Photofragment translational spectroscopy is used to investigate the unimolecular photodissociation of the indenyl radical (C9H7). C9H7 radicals are generated by photodetachment of C9H7 - anions and are dissociated at 248 nm (5.00 eV) and 193 nm (6.42 eV). The following product channels are definitively observed at both wavelengths: C2H2 + C7H5, C2H2 + C3H3 + C4H2, and C2H2 + C2H2 + C5H3. The three-body product channels are energetically inaccessible from single photon excitation at either dissociation wavelength. This observation, in combination with calculated dissociation rates and laser power studies, implies that all dissociation seen in this experiment occurs exclusively through multiphoton processes in which the initial C9H7 radical absorbs two photons sequentially prior to dissociation to two or three fragments. The corresponding translational energy distributions for each product channel peak well below the maximum available energy for two photons and exhibit similar behavior regardless of dissociation wavelength. These results suggest that all products are formed by internal conversion to the ground electronic state, followed by dissociation.
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Affiliation(s)
- Erin N. Sullivan
- Department of Chemistry, University of California, Berkeley, California 94720, USA and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Bethan Nichols
- Department of Chemistry, University of California, Berkeley, California 94720, USA and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Stephen von Kugelgen
- Department of Chemistry, University of California, Berkeley, California 94720, USA and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Gabriel da Silva
- Department of Chemical Engineering, University of Melbourne, Victoria 3010 Australia
| | - Daniel M. Neumark
- Department of Chemistry, University of California, Berkeley, California 94720, USA and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
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Sullivan EN, Nichols B, Neumark DM. Fast beam photofragment translational spectroscopy of the phenoxy radical at 225 nm, 290 nm, and 533 nm. Phys Chem Chem Phys 2019; 21:14270-14277. [PMID: 30566134 DOI: 10.1039/c8cp06818f] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Photodissociation of the phenoxy radical (C6H5O) is investigated using fast beam photofragment translational spectroscopy. Phenoxy radicals are generated through photodetachment of phenoxide anions (C6H5O-) at 532 nm. Following photoexcitation of the radicals at 225 nm (5.51 eV), 290 nm (4.27 eV), or 533 nm (2.33 eV), photofragments are collected in coincidence to determine their masses, translational energy, and scattering angle for each dissociation event. Two-body dissociation yields exclusively CO + C5H5, and three-body dissociation to CO + C2H2 + C3H3 and CO + C5H4 + H is also seen at the two higher energies. The translational energy distributions for two-body dissociation suggest that dissociation occurs via internal conversion to the ground electronic state followed by statistical dissociation. The absorption of an additional 532 nm photon in the photodetachment region provides some C6H5O radicals with an additional 2.33 eV of energy, leading to much of the two-body dissociation observed at 533 nm and the three-body dissociation at the two higher excitation energies.
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Affiliation(s)
- Erin N Sullivan
- Department of Chemistry, University of California, Berkeley, California 94720, USA.
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Ashfold MNR, Ingle RA, Karsili TNV, Zhang J. Photoinduced C–H bond fission in prototypical organic molecules and radicals. Phys Chem Chem Phys 2019; 21:13880-13901. [DOI: 10.1039/c8cp07454b] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
We survey and assess current knowledge regarding the primary photochemistry of hydrocarbon molecules and radicals.
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Affiliation(s)
| | | | | | - Jingsong Zhang
- Department of Chemistry
- University of California at Riverside
- Riverside
- USA
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