1
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He C, Kaiser RI, Lu W, Ahmed M, Reyes Y, Wnuk SF, Mebel AM. Exotic Reaction Dynamics in the Gas-Phase Preparation of Anthracene (C 14H 10) via Spiroaromatic Radical Transients in the Indenyl-Cyclopentadienyl Radical-Radical Reaction. J Am Chem Soc 2023; 145:3084-3091. [PMID: 36701838 DOI: 10.1021/jacs.2c12045] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The gas-phase reaction between the 1-indenyl (C9H7•) radical and the cyclopentadienyl (C5H5•) radical has been investigated for the first time using synchrotron-based mass spectrometry coupled with a pyrolytic reactor. Soft photoionization with tunable vacuum ultraviolet photons afforded for the isomer-selective identification of the production of phenanthrene, anthracene, and benzofulvalene (C14H10). The classical theory prevalent in the literature proposing that radicals combine only at their specific radical centers is challenged by our discovery of an unusual reaction pathway that involves a barrierless combination of a resonantly stabilized hydrocarbon radical with an aromatic radical at the carbon atom adjacent to the traditional C1 radical center; this unconventional addition is followed by substantial isomerization into phenanthrene and anthracene via a category of exotic spiroaromatic intermediates. This result leads to a deeper understanding of the evolution of the cosmic carbon budget and provides new methodologies for the bottom-up synthesis of unique spiroaromatics that may be relevant for the synthesis of more complex aromatic carbon skeletons in deep space.
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Affiliation(s)
- Chao He
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, United States
| | - Ralf I Kaiser
- Department of Chemistry, University of Hawai'i 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
| | - Yahaira Reyes
- Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, United States
| | - Stanislaw F Wnuk
- Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, United States
| | - Alexander M Mebel
- Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, United States
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2
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He C, Kaiser RI, Lu W, Ahmed M, Pivovarov PS, Kuznetsov OV, Zagidullin MV, Mebel AM. Unconventional Pathway in the Gas-Phase Synthesis of 9H-Fluorene (C 13 H 10 ) via the Radical-Radical Reaction of Benzyl (C 7 H 7 ) with Phenyl (C 6 H 5 ). Angew Chem Int Ed Engl 2023; 62:e202216972. [PMID: 36524679 DOI: 10.1002/anie.202216972] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Revised: 12/16/2022] [Accepted: 12/16/2022] [Indexed: 12/23/2022]
Abstract
The simplest polycyclic aromatic hydrocarbon (PAH) carrying a five-membered ring-9H-fluorene (C13 H10 )-is produced isomer-specifically in the gas phase by reacting benzyl (C7 H7 ⋅) with phenyl (C6 H5 ⋅) radicals in a pyrolytic reactor coupled with single photon ionization mass spectrometry. The unconventional mechanism of reaction is supported by theoretical calculations, which first produces diphenylmethane and unexpected 1-(6-methylenecyclohexa-2,4-dienyl)benzene intermediates (C13 H12 ) accessed via addition of the phenyl radical to the ortho position of the benzyl radical. These findings offer convincing evidence for molecular mass growth processes defying conventional wisdom that radical-radical reactions are initiated through recombination at their radical centers. The structure of 9H-fluorene acts as a molecular building block for complex curved nanostructures like fullerenes and nanobowls providing fundamental insights into the hydrocarbon evolution in high temperature settings.
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Affiliation(s)
- Chao He
- Department of Chemistry, University of Hawai'i at Mānoa, Honolulu, HI-96822, USA
| | - Ralf I Kaiser
- Department of Chemistry, University of Hawai'i at Mānoa, Honolulu, HI-96822, USA
| | - Wenchao Lu
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA-94720, USA
| | - Musahid Ahmed
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA-94720, USA
| | - Pavel S Pivovarov
- Samara National Research University, Samara, 443086, Russian Federation
| | - Oleg V Kuznetsov
- Samara National Research University, Samara, 443086, Russian Federation
| | | | - Alexander M Mebel
- Department of Chemistry and Biochemistry, Florida International University, Miami, FL-33199, USA
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3
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Li W, Zhao L, Kaiser RI. A unified reaction network on the formation of five-membered ringed polycyclic aromatic hydrocarbons (PAHs) and their role in ring expansion processes through radical-radical reactions. Phys Chem Chem Phys 2023; 25:4141-4150. [PMID: 36655590 DOI: 10.1039/d2cp05305e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Exploiting a chemical microreactor in combination with an isomer-selective product identification through fragment-free photoionization utilizing tunable vacuum ultraviolet (VUV) light in tandem with the detection of the ionized molecules by a high resolution reflection time-of-flight mass spectrometer (Re-TOF-MS), the present investigation reveals molecular mass growth processes to four distinct polycyclic aromatic hydrocarbons carrying two six- and one five-membered ring (C13H10): 3H-cyclopenta[a]naphthalene, 1H-cyclopenta[b]naphthalene, 1H-cyclopenta[a]naphthalene, and fluorene in the gas phase. Temperatures of 973 and 1023 K simulating conditions in combustion settings along with circumstellar envelopes of carbon-rich stars and planetary nebulae. These reactions highlight the importance of methyl-substituted aromatic reactants (biphenyl, naphthalene) which can be converted to the methylene (-CH2˙) motive by hydrogen abstraction or photolysis. Upon reaction with acetylene, methylene-substituted aromatics carrying a hydrogen atom at the ortho position of the ring can be then converted to cyclopentadiene-annulated aromatics thus providing a versatile pathway to five-membered ring aromatics at elevated temperatures.
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Affiliation(s)
- Wang Li
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029, China.
| | - Long Zhao
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029, China. .,School of Nuclear Science and Technology, University of Science and Technology of China, Hefei, Anhui 230027, China
| | - Ralf I Kaiser
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, HI 96822, USA.
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4
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Couch DE, Zhang AJ, Taatjes CA, Hansen N. Experimental Observation of Hydrocarbon Growth by Resonance‐Stabilized Radical–Radical Chain Reaction. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202110929] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- David E. Couch
- Gas Phase Chemical Physics Department Combustion Research Facility Sandia National Laboratories Livermore CA 94550 USA
| | - Angie J. Zhang
- Gas Phase Chemical Physics Department Combustion Research Facility Sandia National Laboratories Livermore CA 94550 USA
| | - Craig A. Taatjes
- Gas Phase Chemical Physics Department Combustion Research Facility Sandia National Laboratories Livermore CA 94550 USA
| | - Nils Hansen
- Gas Phase Chemical Physics Department Combustion Research Facility Sandia National Laboratories Livermore CA 94550 USA
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Couch DE, Zhang AJ, Taatjes CA, Hansen N. Experimental Observation of Hydrocarbon Growth by Resonance-Stabilized Radical-Radical Chain Reaction. Angew Chem Int Ed Engl 2021; 60:27230-27235. [PMID: 34605134 DOI: 10.1002/anie.202110929] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Indexed: 01/08/2023]
Abstract
Rapid molecular-weight growth of hydrocarbons occurs in flames, in industrial synthesis, and potentially in cold astrochemical environments. A variety of high- and low-temperature chemical mechanisms have been proposed and confirmed, but more facile pathways may be needed to explain observations. We provide laboratory confirmation in a controlled pyrolysis environment of a recently proposed mechanism, radical-radical chain reactions of resonance-stabilized species. The recombination reaction of phenyl (c-C6 H5 ) and benzyl (c-C6 H5 CH2 ) radicals produces both diphenylmethane and diphenylmethyl radicals, the concentration of the latter increasing with rising temperature. A second phenyl addition to the product radical forms both triphenylmethane and triphenylmethyl radicals, confirming the propagation of radical-radical chain reactions under the experimental conditions of high temperature (1100-1600 K) and low pressure (ca. 3 kPa). Similar chain reactions may contribute to particle growth in flames, the interstellar medium, and industrial reactors.
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Affiliation(s)
- David E Couch
- Gas Phase Chemical Physics Department, Combustion Research Facility, Sandia National Laboratories, Livermore, CA, 94550, USA
| | - Angie J Zhang
- Gas Phase Chemical Physics Department, Combustion Research Facility, Sandia National Laboratories, Livermore, CA, 94550, USA
| | - Craig A Taatjes
- Gas Phase Chemical Physics Department, Combustion Research Facility, Sandia National Laboratories, Livermore, CA, 94550, USA
| | - Nils Hansen
- Gas Phase Chemical Physics Department, Combustion Research Facility, Sandia National Laboratories, Livermore, CA, 94550, USA
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Ghildina AR, Zavershinskiy IP, Mebel AM, Vinogradov KY, Bulanova AV, Zhu H. Theoretical Study of the Mechanism and Kinetics of the Oxidation of Cyclopenta[ a]Naphthalenyl Radical C 13H 9 with Molecular Oxygen. J Phys Chem A 2021; 125:6796-6804. [PMID: 34323493 DOI: 10.1021/acs.jpca.1c05421] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Electronic structure/Rice-Ramsperger-Kassel-Marcus Master equation calculations were applied to unravel the oxidation mechanism and kinetics of the cyclopenta[a]naphthalenyl radical with molecular oxygen. The reaction has been shown to proceed through the addition of O2 in the ortho-position in the five-membered ring of C13H9. At low temperatures, the reaction yields a collisionally stabilized C13H9O2 complex, which rapidly decomposes back to the reactants. In the high-temperature regime, above 800, 900, 1125, and 1375 K at pressures of 0.03, 1, 10, and 100 atm, respectively, the reaction forms bimolecular products including 3H-/1H-cyclopenta[a]naphthalen-3-one + OH as the prevailing product together with 1-ethanol-substituted 2-naphthyl radical + CO and 3H-benzo[f]chromen-3-one + H as minor ones, with the branching ratio of the OH elimination channel growing with temperature and the rate constants for the individual bimolecular channels being independent of pressure. The calculated rate constants and product branching for cyclopenta[a]naphthalenyl + O2 closely agree with those reported earlier for the indenyl + O2 reaction and are recommended for the combustion kinetic models for the oxidation reactions of five-membered rings on free edges of larger polycyclic aromatic hydrocarbon molecules. The results also confirm that the oxidation of a π radical located on a five-membered ring with molecular oxygen is very slow.
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Affiliation(s)
- A R Ghildina
- Lebedev Physical Institute, Samara 443011, Russia
| | | | - A M Mebel
- Samara University, Samara 443086, Russia.,Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, United States
| | | | | | - Hong Zhu
- Institute of Modern Catalysis, Beijing University of Chemical Technology, Beijing 100029, People's Republic of China
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7
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Roy T, Ghosal S, Thimmakondu VS. Six Low-Lying Isomers of C 11H 8 Are Unidentified in the Laboratory-A Theoretical Study. J Phys Chem A 2021; 125:4352-4364. [PMID: 34003652 DOI: 10.1021/acs.jpca.1c02247] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Isomers of C11H8 have been theoretically examined using density functional theory and coupled-cluster methods. The current investigation reveals that 2aH-cyclopenta[cd]indene (2), 7-ethynyl-1H-indene (6), 4-ethynyl-1H-indene (7), 6-ethynyl-1H-indene (8), 5-ethynyl-1H-indene (9), and 7bH-cyclopenta[cd]indene (10) remain elusive till date in the laboratory. The puckered low-lying isomer 2 lies at 9 kJ mol-1 below the experimentally known molecule, cyclobuta[de]naphthalene (3), at the fc-CCSD(T)/cc-pVTZ//fc-CCSD(T)/cc-pVDZ level of theory. 2 lies at 36 kJ mol-1 above the thermodynamically most stable and experimentally known isomer, 1H-cyclopenta[cd]indene (1), at the same level. It is identified that 1,2-H transfer from 1 yields 2H-cyclopenta[cd]indene (14) and subsequent 1,2-H shift from 14 yields 2. Appropriate transition states have been identified, and intrinsic reaction coordinate calculations have been carried out at the B3LYP/6-311+G(d,p) level of theory. Recently, 1-ethynyl-1H-indene (11) has been detected using synchrotron-based vacuum ultraviolet ionization mass spectrometry. 2-Ethynyl-1H-indene (4) and 3-ethynyl-1H-indene (5) have been synthetically characterized in the past. While the derivatives of 7bH-cyclopenta[cd]indene (10) have been isolated elsewhere, the parent compound remains unidentified till date in the laboratory. Although C11H8 is a key elemental composition of astronomical interest for the formation of polycyclic aromatic hydrocarbons in the interstellar medium, none of its low-lying isomers have been characterized by rotational spectroscopy though they are having a permanent dipole moment (μ ≠ 0). Therefore, energetic and spectroscopic properties have been computed, and the present investigation necessitates new synthetic studies on C11H8, in particular 2, 6-10, and also rotational spectroscopic studies on all low-lying isomers.
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Affiliation(s)
- Tarun Roy
- Department of Chemistry, National Institute of Technology Durgapur, M G Avenue, Durgapur 713 209, India
| | - Subhas Ghosal
- Department of Chemistry, National Institute of Technology Durgapur, M G Avenue, Durgapur 713 209, India
| | - Venkatesan S Thimmakondu
- Department of Chemistry and Biochemistry, San Diego State University, San Diego 92182-1030, California, United States
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Zhang Y, Xie M, Sun F, Zhang Z, Nie W, Sun X, Hu Y. Proton Transfer in Nitromethane-Ammonia Clusters under VUV Single-Photon Ionization Explored by Infrared Spectroscopy and Theoretical Calculations. J Phys Chem A 2021; 125:3279-3287. [PMID: 33878869 DOI: 10.1021/acs.jpca.1c00255] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
It is known that the acidity and reactivity of the CH bond can be enhanced after ionization. Also, this property plays a pivotal role in proton transfer reaction and in the formation of new molecules. Herein, infrared spectroscopy and high-precision quantum chemical calculations are used to study the neutral and cationic clusters of nitromethane-ammonia (CH3NO2-NH3). It is found that in the neutral cluster, CH3NO2 and NH3 are mainly bonded by three intermolecular hydrogen bonds, in which electrostatic contribution plays a major role. After vacuum ultraviolet (VUV) single-photon ionization of CH3NO2-NH3, the positive charge redistributes from the ionized nitrogen atom of NH3 to the CH3NO2 molecule immediately. Then, the proton of CH3NO2 transfers to NH3 to form a proton-transferred type structure CH2NO2-NH4+, without any effective energy barrier, due to the positive hyperconjugation of cationic nitromethane. A closed loop of positive charge transfer takes place in the CH3NO2-NH3 cluster after VUV ionization. The present work demonstrates that both the proton transfer reaction and charge transfer process have occurred in the ionized CH3NO2-NH3 cluster. Moreover, it is found that the proton transfer reaction is a result of the highly acidic CH bond caused by hyperconjugation between the σ (CH) bond and π orbital.
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Affiliation(s)
- Yu Zhang
- MOE Key Laboratory of Laser Life Science & Guangdong Provincial Key Laboratory of Laser Life Science, Guangzhou Key Laboratory of Spectral Analysis and Functional Probes, College of Biophotonics, South China Normal University, Guangzhou 510631, China
| | - Min Xie
- MOE Key Laboratory of Laser Life Science & Guangdong Provincial Key Laboratory of Laser Life Science, Guangzhou Key Laboratory of Spectral Analysis and Functional Probes, College of Biophotonics, South China Normal University, Guangzhou 510631, China
| | - Fufei Sun
- MOE Key Laboratory of Laser Life Science & Guangdong Provincial Key Laboratory of Laser Life Science, Guangzhou Key Laboratory of Spectral Analysis and Functional Probes, College of Biophotonics, South China Normal University, Guangzhou 510631, China
| | - Zhaoli Zhang
- MOE Key Laboratory of Laser Life Science & Guangdong Provincial Key Laboratory of Laser Life Science, Guangzhou Key Laboratory of Spectral Analysis and Functional Probes, College of Biophotonics, South China Normal University, Guangzhou 510631, China
| | - Wuyi Nie
- MOE Key Laboratory of Laser Life Science & Guangdong Provincial Key Laboratory of Laser Life Science, Guangzhou Key Laboratory of Spectral Analysis and Functional Probes, College of Biophotonics, South China Normal University, Guangzhou 510631, China
| | - Xiaonan Sun
- MOE Key Laboratory of Laser Life Science & Guangdong Provincial Key Laboratory of Laser Life Science, Guangzhou Key Laboratory of Spectral Analysis and Functional Probes, College of Biophotonics, South China Normal University, Guangzhou 510631, China
| | - Yongjun Hu
- MOE Key Laboratory of Laser Life Science & Guangdong Provincial Key Laboratory of Laser Life Science, Guangzhou Key Laboratory of Spectral Analysis and Functional Probes, College of Biophotonics, South China Normal University, Guangzhou 510631, China
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9
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Abstract
This Perspective presents recent advances in our knowledge of the fundamental elementary mechanisms involved in the low- and high-temperature molecular mass growth processes to polycyclic aromatic hydrocarbons in combustion systems and in extraterrestrial environments (hydrocarbon-rich atmospheres of planets and their moons, cold molecular clouds, circumstellar envelopes). Molecular beam studies combined with electronic structure calculations extracted five key elementary mechanisms: Hydrogen Abstraction-Acetylene Addition, Hydrogen Abstraction-Vinylacetylene Addition, Phenyl Addition-DehydroCyclization, Radical-Radical Reactions, and Methylidyne Addition-Cyclization-Aromatization. These studies, summarized here, provide compelling evidence that key classes of aromatic molecules can be synthesized in extreme environments covering low temperatures in molecular clouds (10 K) and hydrocarbon-rich atmospheres of planets and their moons (35-150 K) to high-temperature environments like circumstellar envelopes of carbon-rich Asymptotic Giant Branch Stars stars and combustion systems at temperatures above 1400 K thus shedding light on the aromatic universe we live in.
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Affiliation(s)
- Ralf I Kaiser
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822, United States
| | - Nils Hansen
- Combustion Research Facility, Sandia National Laboratories, Livermore, California 94551, United States
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