1
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Karir G, Mendez-Vega E, Portela-Gonzalez A, Saraswat M, Sander W, Hemberger P. The elusive phenylethynyl radical and its cation: synthesis, electronic structure, and reactivity. Phys Chem Chem Phys 2024; 26:18256-18265. [PMID: 38904382 DOI: 10.1039/d4cp02129k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/22/2024]
Abstract
Alkynyl radicals and cations are crucial reactive intermediates in chemistry, but often evade direct detection. Herein, we report the direct observation of the phenylethynyl radical (C6H5CC˙) and its cation (C6H5CC+), which are two of the most reactive intermediates in organic chemistry. The radical is generated via pyrolysis of (bromoethynyl)benzene at temperatures above 1500 K and is characterized by photoion mass-selected threshold photoelectron spectroscopy (ms-TPES). Photoionization of the phenylethynyl radical yields the phenylethynyl cation, which has never been synthesized due to its extreme electrophilicity. Vibrationally-resolved ms-TPES assisted by ab initio calculations unveiled the complex electronic structure of the phenylethynyl cation, which appears at an adiabatic ionization energy (AIE) of 8.90 ± 0.05 eV and exhibits an uncommon triplet (3B1) ground state, while the closed-shell singlet (1A1) state lies just 2.8 kcal mol-1 (0.12 eV) higher in energy. The reactive phenylethynyl radical abstracts hydrogen to form ethynylbenzene (C6H5CCH) but also isomerizes via H-shift to the o-, m-, and p-ethynylphenyl isomers (C6H4CCH). These radicals are very reactive and undergo ring-opening followed by H-loss to form a mixture of C8H4 triynes, along with low yields of cyclic 3- and 4-ethynylbenzynes (C6H3CCH). At higher temperatures, dehydrogenation from the unbranched C8H4 triynes forms the linear tetraacetylene (C8H2), an astrochemically relevant polyyne.
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Affiliation(s)
- Ginny Karir
- Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum, Bochum 44780, Germany.
| | - Enrique Mendez-Vega
- Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum, Bochum 44780, Germany.
| | | | - Mayank Saraswat
- Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum, Bochum 44780, Germany.
| | - Wolfram Sander
- Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum, Bochum 44780, Germany.
| | - Patrick Hemberger
- Laboratory for Synchrotron Radiation and Femtochemistry, Paul Scherrer Institute (PSI), Villigen CH-5232, Switzerland.
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2
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Izadi ME, Bal KM, Maghari A, Neyts EC. Reaction mechanisms of C( 3P J) and C +( 2P J) with benzene in the interstellar medium from quantum mechanical molecular dynamics simulations. Phys Chem Chem Phys 2021; 23:4205-4216. [PMID: 33586718 DOI: 10.1039/d0cp04542j] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
While spectroscopic data on small hydrocarbons in interstellar media in combination with crossed molecular beam (CMB) experiments have provided a wealth of information on astrochemically relevant species, much of the underlying mechanistic pathways of their formation remain elusive. Therefore, in this work, the chemical reaction mechanisms of C(3PJ) + C6H6 and C+(2P) + C6H6 systems using the quantum mechanical molecular dynamics (QMMD) technique at the PBE0-D3(BJ) level of theory is investigated, mimicking a CMB experiment. Both the dynamics of the reactions as well as the electronic structure for the purpose of the reaction network are evaluated. The method is validated for the first reaction by comparison to the available experimental data. The reaction scheme for the C(3PJ) + C6H6 system covers the literature data, e.g. the major products are the 1,2-didehydrocycloheptatrienyl radical (C7H5) and benzocyclopropenyl radical (C6H5-CH), and it reveals the existence of less common pathways for the first time. The chemistry of the C+(2PJ) + C6H6 system is found to be much richer, and we have found that this is because of more exothermic reactions in this system in comparison to those in the C(3PJ) + C6H6 system. Moreover, using the QMMD simulation, a number of reaction paths have been revealed that produce three distinct classes of reaction products with different ring sizes. All in all, at all the collision energies and orientations, the major product is the heptagon molecular ion for the ionic system. It is also revealed that the collision orientation has a dominant effect on the reaction products in both systems, while the collision energy mostly affects the charged system. These simulations both prove the applicability of this approach to simulate crossed molecular beams, and provide fundamental information on reactions relevant for the interstellar medium.
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Affiliation(s)
- Mohammad Ebrahim Izadi
- Department of Physical Chemistry, School of Chemistry, College of Science, University of Tehran, Tehran, Iran
| | - Kristof M Bal
- Department of Chemistry, Research Group PLASMANT, NANOlab Center of Excellence, University of Antwerp, Universiteitsplein 1, 2610 Antwerp, Belgium.
| | - Ali Maghari
- Department of Physical Chemistry, School of Chemistry, College of Science, University of Tehran, Tehran, Iran
| | - Erik C Neyts
- Department of Chemistry, Research Group PLASMANT, NANOlab Center of Excellence, University of Antwerp, Universiteitsplein 1, 2610 Antwerp, Belgium.
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3
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Jian J, Wu X, Chen M, Zhou M. Boron-Mediated Carbon-Carbon Bond Cleavage and Rearrangement of Benzene Forming the Borepinyl Radical and Borole Derivatives. J Am Chem Soc 2020; 142:10079-10086. [PMID: 32383858 DOI: 10.1021/jacs.0c02131] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The reaction of atomic boron with benzene in solid neon has been investigated by matrix isolation infrared spectroscopy with isotopic substitutions as well as quantum chemical calculations. The reaction is initiated by boron atom addition to benzene in forming an η2-(1, 4) π adduct (A). A borepinyl radical (B) formed by C-C bond insertion is also observed on annealing. The η2-(1,4) π adduct photoisomerizes to an unprecedented borole substituted vinyl radical intermediate (C) via ring-opening and rearrangement reactions involving an antiaromatic borole subunit. A previously unconsidered 1-ethynyl-2-dihydro-1H-borole radical (D) is generated as the final product under UV light irradiation. The results presented herein give new insight into the benzene carbon-carbon bond cleavage and rearrangement reactions mediated by a nonmetal and provide a possible route for the construction of heterocyclic borepinyl and borole species via benzene ring opening and rearrangement reactions.
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Affiliation(s)
- Jiwen Jian
- Hangzhou Institute of Advanced Studies, Zhejiang Normal University, 1108 Gengwen Road, Hangzhou 311231, China
| | - Xuan Wu
- Collaborative Innovation Center of Chemistry for Energy Materials, Department of Chemistry, Shanghai Key Laboratory of Molecular Catalysts and Innovative materials, Fudan University, Shanghai 200433, China
| | - Mohua Chen
- Collaborative Innovation Center of Chemistry for Energy Materials, Department of Chemistry, Shanghai Key Laboratory of Molecular Catalysts and Innovative materials, Fudan University, Shanghai 200433, China
| | - Mingfei Zhou
- Collaborative Innovation Center of Chemistry for Energy Materials, Department of Chemistry, Shanghai Key Laboratory of Molecular Catalysts and Innovative materials, Fudan University, Shanghai 200433, China
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4
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McCabe M, Hemberger P, Reusch E, Bodi A, Bouwman J. Off the Beaten Path: Almost Clean Formation of Indene from the ortho-Benzyne + Allyl Reaction. J Phys Chem Lett 2020; 11:2859-2863. [PMID: 32202794 PMCID: PMC7168585 DOI: 10.1021/acs.jpclett.0c00374] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Accepted: 03/23/2020] [Indexed: 06/07/2023]
Abstract
Polycyclic aromatic hydrocarbons (PAHs) play an important role in chemistry both in the terrestrial setting and in the interstellar medium. Various, albeit often inefficient, chemical mechanisms have been proposed to explain PAH formation, but few yield polycyclic hydrocarbons cleanly. Alternative and quite promising pathways have been suggested to address these shortcomings with key starting reactants including resonance stabilized radicals (RSRs) and o-benzyne. Here we report on a combined experimental and theoretical study of the reaction allyl + o-benzyne. Indene was found to be the primary product and statistical modeling predicts only 0.1% phenylallene and 0.1% 3-phenyl-1-propyne as side products. The quantitative and likely barrierless formation of indene yields important insights into the role resonance stabilized radicals play in the formation of polycyclic hydrocarbons.
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Affiliation(s)
- Morgan
N. McCabe
- Laboratory
for Astrophysics, Leiden Observatory, Leiden
University, P.O. Box 9513, 2300 RA Leiden, The Netherlands
| | - Patrick Hemberger
- Laboratory
for Synchrotron Radiation and Femtochemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Engelbert Reusch
- Institute
of Physical and Theoretical Chemistry, University
of Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - Andras Bodi
- Laboratory
for Synchrotron Radiation and Femtochemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Jordy Bouwman
- Laboratory
for Astrophysics, Leiden Observatory, Leiden
University, P.O. Box 9513, 2300 RA Leiden, The Netherlands
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5
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Li H, Suits AG. Universal crossed beam imaging studies of polyatomic reaction dynamics. Phys Chem Chem Phys 2020; 22:11126-11138. [DOI: 10.1039/d0cp00522c] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Crossed-beam imaging studies of polyatomic reactions show surprising dynamics not anticipated by extrapolation from smaller model systems.
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Affiliation(s)
- Hongwei Li
- Department of Chemistry
- University of Missouri
- Columbia
- USA
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6
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A Barrierless Pathway Accessing the C 9H 9 and C 9H 8 Potential Energy Surfaces via the Elementary Reaction of Benzene with 1-Propynyl. Sci Rep 2019; 9:17595. [PMID: 31772216 PMCID: PMC6879741 DOI: 10.1038/s41598-019-53987-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Accepted: 11/07/2019] [Indexed: 11/16/2022] Open
Abstract
The crossed molecular beams reactions of the 1-propynyl radical (CH3CC; X2A1) with benzene (C6H6; X1A1g) and D6-benzene (C6D6; X1A1g) were conducted to explore the formation of C9H8 isomers under single-collision conditions. The underlying reaction mechanisms were unravelled through the combination of the experimental data with electronic structure and statistical RRKM calculations. These data suggest the formation of 1-phenyl-1-propyne (C6H5CCCH3) via the barrierless addition of 1-propynyl to benzene forming a low-lying doublet C9H9 intermediate that dissociates by hydrogen atom emission via a tight transition state. In accordance with our experiments, RRKM calculations predict that the thermodynamically most stable isomer – the polycyclic aromatic hydrocarbon (PAH) indene – is not formed via this reaction. With all barriers lying below the energy of the reactants, this reaction is viable in the cold interstellar medium where several methyl-substituted molecules have been detected. Its underlying mechanism therefore advances our understanding of how methyl-substituted hydrocarbons can be formed under extreme conditions such as those found in the molecular cloud TMC-1. Implications for the chemistry of the 1-propynyl radical in astrophysical environments are also discussed.
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7
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Zhao L, Prendergast MB, Kaiser RI, Xu B, Lu W, Ablikim U, Ahmed M, Oleinikov AD, Azyazov VN, Mebel AM, Howlader AH, Wnuk SF. Reactivity of the Indenyl Radical (C 9 H 7 ) with Acetylene (C 2 H 2 ) and Vinylacetylene (C 4 H 4 ). Chemphyschem 2019; 20:1437-1447. [PMID: 30938059 DOI: 10.1002/cphc.201900052] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2019] [Revised: 02/28/2019] [Indexed: 11/09/2022]
Abstract
The reactions of the indenyl radicals with acetylene (C2 H2 ) and vinylacetylene (C4 H4 ) is studied in a hot chemical reactor coupled to synchrotron based vacuum ultraviolet ionization mass spectrometry. These experimental results are combined with theory to reveal that the resonantly stabilized and thermodynamically most stable 1-indenyl radical (C9 H7 . ) is always formed in the pyrolysis of 1-, 2-, 6-, and 7-bromoindenes at 1500 K. The 1-indenyl radical reacts with acetylene yielding 1-ethynylindene plus atomic hydrogen, rather than adding a second acetylene molecule and leading to ring closure and formation of fluorene as observed in other reaction mechanisms such as the hydrogen abstraction acetylene addition or hydrogen abstraction vinylacetylene addition pathways. While this reaction mechanism is analogous to the bimolecular reaction between the phenyl radical (C6 H5 . ) and acetylene forming phenylacetylene (C6 H5 CCH), the 1-indenyl+acetylene→1-ethynylindene+hydrogen reaction is highly endoergic (114 kJ mol-1 ) and slow, contrary to the exoergic (-38 kJ mol-1 ) and faster phenyl+acetylene→phenylacetylene+hydrogen reaction. In a similar manner, no ring closure leading to fluorene formation was observed in the reaction of 1-indenyl radical with vinylacetylene. These experimental results are explained through rate constant calculations based on theoretically derived potential energy surfaces.
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Affiliation(s)
- Long Zhao
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii, 96822, USA
| | - Matthew B Prendergast
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii, 96822, USA
| | - Ralf I Kaiser
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii, 96822, USA
| | - Bo Xu
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Wenchao Lu
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Utuq Ablikim
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Musahid Ahmed
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | | | | | - Alexander M Mebel
- Samara National Research University, Samara, 443086, Russia.,Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA
| | - A Hasan Howlader
- Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA
| | - Stanislaw F Wnuk
- Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA
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8
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Rezgui Y. Role of hydrogen enrichment on acetylene emission during benzene oxidation. KINETICS AND CATALYSIS 2017. [DOI: 10.1134/s0023158417030107] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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9
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Mebel AM, Landera A, Kaiser RI. Formation Mechanisms of Naphthalene and Indene: From the Interstellar Medium to Combustion Flames. J Phys Chem A 2017; 121:901-926. [DOI: 10.1021/acs.jpca.6b09735] [Citation(s) in RCA: 100] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Alexander M. Mebel
- Department
of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, United States
| | - Alexander Landera
- Chemical
Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Ralf I. Kaiser
- Department
of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822, United States
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10
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Zhao L, Yang T, Kaiser RI, Troy TP, Xu B, Ahmed M, Alarcon J, Belisario-Lara D, Mebel AM, Zhang Y, Cao C, Zou J. A vacuum ultraviolet photoionization study on high-temperature decomposition of JP-10 (exo-tetrahydrodicyclopentadiene). Phys Chem Chem Phys 2017; 19:15780-15807. [DOI: 10.1039/c7cp01571b] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
High-temperature pyrolysis of JP-10 in flow reactors were performed both experimentally and theoretically. Dozens of products were detected and the decomposition pathways of JP-10 were discussed.
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Affiliation(s)
- Long Zhao
- Department of Chemistry
- University of Hawaii at Manoa
- Honolulu
- USA
| | - Tao Yang
- Department of Chemistry
- University of Hawaii at Manoa
- Honolulu
- USA
| | - Ralf I. Kaiser
- Department of Chemistry
- University of Hawaii at Manoa
- Honolulu
- USA
| | - Tyler P. Troy
- Chemical Sciences Division
- Lawrence Berkeley National Laboratory
- Berkeley
- USA
| | - Bo Xu
- Chemical Sciences Division
- Lawrence Berkeley National Laboratory
- Berkeley
- USA
| | - Musahid Ahmed
- Chemical Sciences Division
- Lawrence Berkeley National Laboratory
- Berkeley
- USA
| | - Juan Alarcon
- Department of Chemistry and Biochemistry
- Florida International University
- Miami
- USA
| | | | - Alexander M. Mebel
- Department of Chemistry and Biochemistry
- Florida International University
- Miami
- USA
| | - Yan Zhang
- National Synchrotron Radiation Laboratory
- University of Science and Technology of China
- Hefei
- P. R. China
| | - Chuangchuang Cao
- National Synchrotron Radiation Laboratory
- University of Science and Technology of China
- Hefei
- P. R. China
| | - Jiabiao Zou
- Key Laboratory for Power Machinery and Engineering of MOE
- Shanghai Jiao Tong University
- Shanghai 200240
- P. R. China
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11
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McIntosh GJ, Russell DK. Role of hydrogen abstraction acetylene addition mechanisms in the formation of chlorinated naphthalenes. 1. A quantum chemical investigation. J Phys Chem A 2014; 118:12192-204. [PMID: 25419897 DOI: 10.1021/jp508979u] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The addition of chloroacetylene or tetrachlorovinylacetylene to 2,4,5-trichlorophenyl radicals, leading to the formation of tetra-, penta-, and hexachloronaphthalene congeners, has been explored at the M06-2X/6-311+G(3df,3p)//B3LYP/6-31G(d) level of theory. The accuracy of this method was justified by comparing the barriers of several pertinent reactions against energies from single point calculations at the B3LYP/cc-pVDZ, CCSD(T)/6-31G(d), and G2MS levels. Bittner-Howard and Frenklach hydrogen abstraction acetylene addition mechanisms were developed, as was a channel based on acetylene additions to chlorinated [4.2.0]octa-1,3,5-trien-7-yl congeners. While the latter channel exhibits relatively high C2HCl addition barriers and may be a minor growth channel at best, both the Bittner-Howard and Frenklach sequences appear facile. In all mechanisms, the additions of C2HCl leading to a β-chlorinated adduct is favored by ∼15 kJ mol(-1) relative to the α-chlorinated analogue, and the addition products typically access a variety of facile cyclization channels. The α-chlorinated product of C2HCl addition to 2,4,5-trichlorophenyl, however, undergoes a particularly rapid Cl-loss leading to 1-ethynyl-2,4,5-trichlorobenzene, effectively shutting down further growth. Generalization implies that α-chlorinated C6H5-CH═CH congeners do not participate in growth reactions. Addition of 2,4,5-trichlorophenyl to the C≡C bond of tetrachlorovinylacetylene and subsequent cyclization is found to be a facile route to hexachloronaphthalene formation and may be operative in fully chlorinated systems where the C6Cl5-CCl═CCl congeners cannot participate in the major growth processes.
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Affiliation(s)
- Grant J McIntosh
- School of Chemical Sciences, University of Auckland , Private Bag 92019, Auckland 1142, New Zealand
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12
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McIntosh GJ, Russell DK. Role of hydrogen abstraction acetylene addition mechanisms in the formation of chlorinated naphthalenes. 2. Kinetic modeling and the detailed mechanism of ring closure. J Phys Chem A 2014; 118:12205-20. [PMID: 25420011 DOI: 10.1021/jp5089806] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The dominant formation mechanisms of chlorinated phenylacetylenes, naphthalenes, and phenylvinylacetylenes in relatively low pressure and temperature (∼40 Torr and 1000 K) pyrolysis systems are explored. Mechanism elucidation is achieved through a combination of theoretical and experimental techniques, the former employing a novel simplification of kinetic modeling which utilizes rate constants in a probabilistic framework. Contemporary formation schemes of the compounds of interest generally require successive additions of acetylene to phenyl radicals. As such, infrared laser powered homogeneous pyrolyses of dichloro- or trichloroethylene were perturbed with 1,2,4- or 1,2,3-trichlorobenzene. The resulting changes in product identities were compared with the major products expected from conventional pathways, aided by the results of our previous computational work. This analysis suggests that a Bittner-Howard growth mechanism, with a novel amendment to the conventional scheme made just prior to ring closure, describes the major products well. Expected products from a number of other potentially operative channels are shown to be incongruent with experiment, further supporting the role of Bittner-Howard channels as the unique pathway to naphthalene growth. A simple quantitative analysis which performs very well is achieved by considering the reaction scheme as a probability tree, with relative rate constants being cast as branching probabilities. This analysis describes all chlorinated phenylacetylene, naphthalene, and phenylvinylacetylene congeners. The scheme is then tested in a more general system, i.e., not enforcing a hydrogen abstraction/acetylene addition mechanism, by pyrolyzing mixtures of di- and trichloroethylene without the addition of an aromatic precursor. The model indicates that these mechanisms are still likely to be operative.
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Affiliation(s)
- Grant J McIntosh
- School of Chemical Sciences, University of Auckland , Private Bag 92019, Auckland 1142, New Zealand
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13
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Parker DSN, Kaiser RI, Troy TP, Ahmed M. Hydrogen abstraction/acetylene addition revealed. Angew Chem Int Ed Engl 2014; 53:7740-4. [PMID: 24953850 DOI: 10.1002/anie.201404537] [Citation(s) in RCA: 94] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2014] [Indexed: 11/06/2022]
Abstract
For almost half a century, polycyclic aromatic hydrocarbons (PAHs) have been proposed to play a key role in the astrochemical evolution of the interstellar medium (ISM) and in the chemistry of combustion systems. However, even the most fundamental reaction mechanism assumed to lead to the simplest PAH naphthalene--the hydrogen abstraction-acetylene addition (HACA) mechanism--has eluded experimental observation. Here, by probing the phenylacetylene (C8 H6 ) intermediate together with naphthalene (C10 H8 ) under combustion-like conditions by photo-ionization mass spectrometry, the very first direct experimental evidence for the validity of the HACA mechanism which so far had only been speculated theoretically is reported.
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Affiliation(s)
- Dorian S N Parker
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, HI 96822, (USA) http://www.chem.hawaii.edu/Bil301/welcome.html
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14
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Parker DSN, Kaiser RI, Troy TP, Ahmed M. Hydrogen Abstraction/Acetylene Addition Revealed. Angew Chem Int Ed Engl 2014. [DOI: 10.1002/ange.201404537] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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15
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Parker DS, Yang T, Kaiser RI, Landera A, Mebel AM. On the formation of ethynylbiphenyl (C14D5H5; C6D5C6H4CCH) isomers in the reaction of D5-phenyl radicals (C6D5; X2A1) with phenylacetylene (C6H5C2H; X1A1) under single collision conditions. Chem Phys Lett 2014. [DOI: 10.1016/j.cplett.2014.02.013] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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16
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Dangi BB, Parker DSN, Kaiser RI, Jamal A, Mebel AM. A Combined Experimental and Theoretical Study on the Gas-Phase Synthesis of Toluene under Single Collision Conditions. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201302344] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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17
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Dangi BB, Parker DSN, Kaiser RI, Jamal A, Mebel AM. A Combined Experimental and Theoretical Study on the Gas-Phase Synthesis of Toluene under Single Collision Conditions. Angew Chem Int Ed Engl 2013; 52:7186-9. [DOI: 10.1002/anie.201302344] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2013] [Indexed: 11/05/2022]
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18
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Zhang F, Kaiser RI, Golan A, Ahmed M, Hansen N. A VUV Photoionization Study of the Combustion-Relevant Reaction of the Phenyl Radical (C6H5) with Propylene (C3H6) in a High Temperature Chemical Reactor. J Phys Chem A 2012; 116:3541-6. [DOI: 10.1021/jp300875s] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Fangtong Zhang
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822,
United States
| | - Ralf I. Kaiser
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822,
United States
| | - Amir Golan
- 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
| | - Nils Hansen
- Combustion
Research Facility, Sandia National Laboratories, Livermore, California 94551, United States
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19
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Kaiser RI, Parker DSN, Goswami M, Zhang F, Kislov VV, Mebel AM, Aguilera-Iparraguirre J, Green WH. Crossed beam reaction of phenyl and D5-phenyl radicals with propene and deuterated counterparts—competing atomic hydrogen and methyl loss pathways. Phys Chem Chem Phys 2012; 14:720-9. [DOI: 10.1039/c1cp22758k] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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20
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Parker DSN, Zhang F, Kim YS, Kaiser RI, Landera A, Mebel AM. On the formation of phenyldiacetylene (C6H5CCCCH) and D5-phenyldiacetylene (C6D5CCCCH) studied under single collision conditions. Phys Chem Chem Phys 2012; 14:2997-3003. [DOI: 10.1039/c2cp22695b] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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Parker DSN, Zhang F, Kaiser RI. Phenoxy Radical (C6H5O) Formation under Single Collision Conditions from Reaction of the Phenyl Radical (C6H5, X2A1) with Molecular Oxygen (O2, X3Σg–): The Final Chapter? J Phys Chem A 2011; 115:11515-8. [DOI: 10.1021/jp206160q] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Dorian S. N. Parker
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822-2275, United States
| | - Fangtong Zhang
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822-2275, United States
| | - Ralf I. Kaiser
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822-2275, United States
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22
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Goswami M, Arunan E. Microwave spectroscopic and theoretical studies on the phenylacetylene⋯H2O complex: C–H⋯O and O–H⋯π hydrogen bonds as equal partners. Phys Chem Chem Phys 2011; 13:14153-62. [DOI: 10.1039/c1cp20690g] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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23
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Jones B, Zhang F, Maksyutenko P, Mebel AM, Kaiser RI. Crossed molecular beam study on the formation of phenylacetylene and its relevance to Titan's atmosphere. J Phys Chem A 2010; 114:5256-62. [PMID: 20369875 DOI: 10.1021/jp912054p] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The crossed molecular beam experiment of the deuterated ethynyl radical (C(2)D; X(2)Sigma(+)) with benzene [C(6)H(6)(X(1)A(1g))] and its fully deuterated analog [C(6)D(6)(X(1)A(1g))] was conducted at a collision energy of 58.1 kJ mol(-1). Our experimental data suggest the formation of the phenylacetylene-d(6) via indirect reactive scattering dynamics through a long-lived reaction intermediate; the reaction is initiated by a barrierless addition of the ethynyl-d(1) radical to benzene-d(6). This initial collision complex was found to decompose via a tight exit transition state located about 42 kJ mol(-1) above the separated products; here, the deuterium atom is ejected almost perpendicularly to the rotational plane of the decomposing intermediate and almost parallel to the total angular momentum vector. The overall experimental exoergicity of the reaction is shown to be 121 +/- 10 kJ mol(-1); this compares nicely with the computed reaction energy of -111 kJ mol(-1). Even though the experiment was conducted at a collisional energy higher than equivalent temperatures typically found in the atmosphere of Titan (94 K and higher), the reaction may proceed in Titan's atmosphere as it involves no entrance barrier, all transition states involved are below the energy of the separated reactants, and the reaction is exoergic. Further, the phenylacetylene was found to be the sole reaction product.
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Affiliation(s)
- Brant Jones
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, USA
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24
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Reaction dynamics of the phenyl radical (C6H5) with 1-butyne (HCCC2H5) and 2-butyne (CH3CCCH3). Chem Phys Lett 2009. [DOI: 10.1016/j.cplett.2009.09.057] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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25
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26
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Gu X, Kaiser RI. Reaction dynamics of phenyl radicals in extreme environments: a crossed molecular beam study. Acc Chem Res 2009; 42:290-302. [PMID: 19053235 DOI: 10.1021/ar8001365] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Polycyclic aromatic hydrocarbons (PAHs)organic compounds that consist of fused benzene ringsand their hydrogen-deficient precursors have attracted extensive interest from combustion scientists, organic chemists, astronomers, and planetary scientists. On Earth, PAHs are toxic combustion products and a source of air pollution. In the interstellar medium, research suggests that PAHs play a role in unidentified infrared emission bands, diffuse interstellar bands, and the synthesis of precursor molecules to life. To build clean combustion devices and to understand the astrochemical evolution of the interstellar medium, it will be critical to understand the elementary reaction mechanisms under single collision conditions by which these molecules form in the gas phase. Until recently, this work had been hampered by the difficulty in preparing a large concentration of phenyl radicals, but the phenyl radical represents one of the most important radical species to trigger PAH formation in high-temperature environments. However, we have developed a method for producing these radical species and have undertaken a systematic experimental investigation. In this Account, we report on the chemical dynamics of the phenyl radical (C(6)H(5)) reactions with the unsaturated hydrocarbons acetylene (C(2)H(2)), ethylene (C(2)H(4)), methylacetylene (CH(3)CCH), allene (H(2)CCCH(2)), propylene (CH(3)CHCH(2)), and benzene (C(6)H(6)) utilizing the crossed molecular beams approach. For nonsymmetric reactants such as methylacetylene and propylene, steric effects and the larger cones of acceptance drive the addition of the phenyl radical to the nonsubstituted carbon atom of the hydrocarbon reactant. Reaction intermediates decomposed via atomic hydrogen loss pathways. In the phenyl-propylene system, the longer lifetime of the reaction intermediate yielded a more efficient energy randomization compared with the phenyl-methylacetylene system. Therefore, two reaction channels were open: hydrogen losses from the vinyl and from the methyl groups. All fragmentation pathways involved tight exit transition states. In the range of collision energies investigated, the reactions are dictated by phenyl radical addition-hydrogen atom elimination pathways. We did not observe ring closure processes with the benzene ring. Our investigations present an important step toward a systematic investigation of phenyl radical reactions under single collision conditions similar to those found in combustion flames and in high-temperature interstellar environments. Future experiments at lower collision energies may enhance the lifetimes of the reaction intermediates, which could open up competing ring closure channels to form bicyclic reaction products.
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Affiliation(s)
- Xibin Gu
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822
| | - Ralf I. Kaiser
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822
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Gu X, Zhang F, Kaiser RI. A Crossed Molecular Beam Study of the Phenyl Radical Reaction with 1,3-Butadiene and its Deuterated Isotopologues. J Phys Chem A 2009; 113:998-1006. [DOI: 10.1021/jp809364v] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Xibin Gu
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822
| | - Fangtong Zhang
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822
| | - Ralf I. Kaiser
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822
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28
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Landera A, Mebel AM, Kaiser RI. Theoretical study of the reaction mechanism of ethynyl radical with benzene and related reactions on the C8H7 potential energy surface. Chem Phys Lett 2008. [DOI: 10.1016/j.cplett.2008.05.043] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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29
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Zhang F, Gu X, Guo Y, Kaiser RI. Reaction Dynamics of Phenyl Radicals (C6H5) with Propylene (CH3CHCH2) and Its Deuterated Isotopologues. J Phys Chem A 2008; 112:3284-90. [DOI: 10.1021/jp711146a] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Fangtong Zhang
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822
| | - Xibin Gu
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822
| | - Ying Guo
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822
| | - Ralf I. Kaiser
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822
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Crossed beam reaction of the phenyl radical, (C6H5, X2A′) with molecular oxygen (O2,X3Σg-): Observation of the phenoxy radical, (C6H5O, X2A′). Chem Phys Lett 2007. [DOI: 10.1016/j.cplett.2007.09.022] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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