1
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Guillaume T, Hays BM, Gupta D, Cooke IR, Abdelkader Khedaoui O, Hearne TS, Drissi M, Sims IR. Product-specific reaction kinetics in continuous uniform supersonic flows probed by chirped-pulse microwave spectroscopy. J Chem Phys 2024; 160:204201. [PMID: 38808747 DOI: 10.1063/5.0203428] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2024] [Accepted: 05/06/2024] [Indexed: 05/30/2024] Open
Abstract
Experimental studies of the products of elementary gas-phase chemical reactions occurring at low temperatures (<50 K) are very scarce, but of importance for fundamental studies of reaction dynamics, comparisons with high-level quantum dynamical calculations, and, in particular, for providing data for the modeling of cold astrophysical environments, such as dense interstellar clouds, the atmospheres of the outer planets, and cometary comae. This study describes the construction and testing of a new apparatus designed to measure product branching fractions of elementary bimolecular gas-phase reactions at low temperatures. It combines chirped-pulse Fourier transform millimeter wave spectroscopy with continuous uniform supersonic flows and high repetition rate laser photolysis. After a comprehensive description of the apparatus, the experimental procedures and data processing protocols used for signal recovery, the capabilities of the instrument are explored by the study of the photodissociation of acrylonitrile and the detection of two of its photoproducts, HC3N and HCN. A description is then given of a study of the reactions of the CN radical with C2H2 at 30 K, detecting the HC3N product, and with C2H6 at 10 K, detecting the HCN product. A calibration of these two products is finally attempted using the photodissociation of acrylonitrile as a reference process. The limitations and possible improvements in the instrument are discussed in conclusion.
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Affiliation(s)
| | | | | | | | | | | | | | - Ian R Sims
- Univ Rennes, CNRS, IPR (Institut de Physique de Rennes) - UMR 6251, F-35000 Rennes, France
- Institut universitaire de France (IUF), France
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2
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Nixon CA. The Composition and Chemistry of Titan's Atmosphere. ACS EARTH & SPACE CHEMISTRY 2024; 8:406-456. [PMID: 38533193 PMCID: PMC10961852 DOI: 10.1021/acsearthspacechem.2c00041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 11/02/2023] [Accepted: 02/02/2024] [Indexed: 03/28/2024]
Abstract
In this review I summarize the current state of knowledge about the composition of Titan's atmosphere and our current understanding of the suggested chemistry that leads to that observed composition. I begin with our present knowledge of the atmospheric composition, garnered from a variety of measurements including Cassini-Huygens, the Atacama Large Millimeter/submillimeter Array, and other ground- and space-based telescopes. This review focuses on the typical vertical profiles of gases at low latitudes rather than global and temporal variations. The main body of the review presents a chemical description of how complex molecules are believed to arise from simpler species, considering all known "stable" molecules-those that have been uniquely identified in the neutral atmosphere. The last section of the review is devoted to the gaps in our present knowledge of Titan's chemical composition and how further work may fill those gaps.
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Affiliation(s)
- Conor A. Nixon
- Planetary Systems Laboratory, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, Maryland 20771, United
States
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3
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Ortega P, Gil-Guerrero S, González-Sánchez L, Sanz-Sanz C, Jambrina PG. Spin-Forbidden Addition of Molecular Oxygen to Stable Enol Intermediates-Decarboxylation of 2-Methyl-1-tetralone-2-carboxylic Acid. Int J Mol Sci 2023; 24:ijms24087424. [PMID: 37108586 PMCID: PMC10138960 DOI: 10.3390/ijms24087424] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Revised: 04/12/2023] [Accepted: 04/13/2023] [Indexed: 04/29/2023] Open
Abstract
The deprotonation of an organic substrate is a common preactivation step for the enzymatic cofactorless addition of O2 to this substrate, as it promotes charge-transfer between the two partners, inducing intersystem crossing between the triplet and singlet states involved in the process. Nevertheless, the spin-forbidden addition of O2 to uncharged ligands has also been observed in the laboratory, and the detailed mechanism of how the system circumvents the spin-forbiddenness of the reaction is still unknown. One of these examples is the cofactorless peroxidation of 2-methyl-3,4-dihydro-1-naphthol, which will be studied computationally using single and multi-reference electronic structure calculations. Our results show that the preferred mechanism is that in which O2 picks a proton from the substrate in the triplet state, and subsequently hops to the singlet state in which the product is stable. For this reaction, the formation of the radical pair is associated with a higher barrier than that associated with the intersystem crossing, even though the absence of the negative charge leads to relatively small values of the spin-orbit coupling.
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Affiliation(s)
- Pablo Ortega
- Departamento de Química-Física, Universidad de Salamanca, 37008 Salamanca, Spain
| | - Sara Gil-Guerrero
- Departamento de Química-Física, Universidad de Salamanca, 37008 Salamanca, Spain
- CICECO-Aveiro Institute of Materials, University of Aveiro, 3810-193 Aveiro, Portugal
| | | | - Cristina Sanz-Sanz
- Departamento de Química Física Aplicada, Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - Pablo G Jambrina
- Departamento de Química-Física, Universidad de Salamanca, 37008 Salamanca, Spain
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4
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Blitz MA, Onel L, Robertson SH, Seakins PW. Studies on the Kinetics of the CH + H 2 Reaction and Implications for the Reverse Reaction, 3CH 2 + H. J Phys Chem A 2023; 127:2367-2375. [PMID: 36857400 PMCID: PMC10026075 DOI: 10.1021/acs.jpca.2c08097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/02/2023]
Abstract
The reaction of CH radicals with H2 has been studied by the use of laser flash photolysis, probing CH decays under pseudo-first-order conditions using laser-induced fluorescence (LIF) over the temperature range 298-748 K at pressures of ∼5-100 Torr. Careful data analysis was required to separate the CH LIF signal at ∼428 nm from broad background fluorescence, and this interference increased with temperature. We believe that this interference may have been the source of anomalous pressure behavior reported previously in the literature (Brownsword, R. A.; J. Chem. Phys. 1997, 106, 7662-7677). The rate coefficient k1 shows complex behavior: at low pressures, the main route for the CH3* formed from the insertion of CH into H2 is the formation of 3CH2 + H, and as the pressure is increased, CH3* is increasingly stabilized to CH3. The kinetic data on CH + H2 have been combined with experimental shock tube data on methyl decomposition and literature thermochemistry within a master equation program to precisely determine the rate coefficient of the reverse reaction, 3CH2 + H → CH + H2. The resulting parametrization is kCH2+H(T) = (1.69 ± 0.11) × 10-10 × (T/298 K)(0.05±0.010) cm3 molecule-1 s-1, where the errors are 1σ.
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Affiliation(s)
- Mark A Blitz
- School of Chemistry, University of Leeds, Leeds LS2 9JT, U.K
- NCAS, University of Leeds, Leeds LS2 9JT, U.K
| | - Lavinia Onel
- School of Chemistry, University of Leeds, Leeds LS2 9JT, U.K
| | | | - Paul W Seakins
- School of Chemistry, University of Leeds, Leeds LS2 9JT, U.K
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5
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Reimann M, Teichmann E, Hecht S, Kaupp M. Solving the Azobenzene Entropy Puzzle: Direct Evidence for Multi-State Reactivity. J Phys Chem Lett 2022; 13:10882-10888. [PMID: 36394331 DOI: 10.1021/acs.jpclett.2c02838] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
A solution to the azobenzene "entropy puzzle" [ J. Phys.: Condens. Matter, 2017, 29, 314002] is provided. Previous computational studies of the thermal Z → E (back-)isomerization of azobenzene could not describe the experimentally observed large negative activation entropies. Here it is shown that the experimental results are only compatible with a more complicated multistate rotation mechanism that involves a triplet excited state. Using nonadiabatic transition state theory, close to perfect agreement is achieved between all calculated and experimental Eyring parameters. We also provide new experiments that indicate the presence of a noticeable external heavy-atom effect, which is a direct result of spin-orbit coupling effects being important in the proposed mechanism. These results suggest a reexamination of the mechanisms of related thermal double bond isomerizations in other systems in cases when an excited state of triplet (or other) multiplicity becomes thermally accessible during a rotation process.
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Affiliation(s)
- Marc Reimann
- Theoretische Chemie/Quantenchemie, Institut für Chemie, Technische Universität Berlin, Sekr. C7, Straße des 17. Juni 135, 10623, Berlin, Germany
| | - Ellen Teichmann
- Institut für Chemie, Humboldt-Universität zu Berlin, Brook-Taylor-Straße 2, 12489, Berlin, Germany
| | - Stefan Hecht
- Institut für Chemie, Humboldt-Universität zu Berlin, Brook-Taylor-Straße 2, 12489, Berlin, Germany
- DWI-Leibniz Institute for Interactive Materials, Forckenbeckstraße 50, 52074, Aachen, Germany
- Institute of Technical and Macromolecular Chemistry, RWTH Aachen University, Worringer Weg 2, 52074, Aachen, Germany
| | - Martin Kaupp
- Theoretische Chemie/Quantenchemie, Institut für Chemie, Technische Universität Berlin, Sekr. C7, Straße des 17. Juni 135, 10623, Berlin, Germany
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6
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Yang Z, Doddipatla S, He C, Goettl SJ, Kaiser RI, Jasper AW, Gomes ACR, Galvão BRL. Can third-body stabilisation of bimolecular collision complexes in cold molecular clouds happen? Mol Phys 2022. [DOI: 10.1080/00268976.2022.2134832] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Affiliation(s)
- Zhenghai Yang
- Department of Chemistry, University of Hawai’i at Manoa, Honolulu, HI, USA
| | | | - Chao He
- Department of Chemistry, University of Hawai’i at Manoa, Honolulu, HI, USA
| | - Shane J. Goettl
- Department of Chemistry, University of Hawai’i at Manoa, Honolulu, HI, USA
| | - Ralf I. Kaiser
- Department of Chemistry, University of Hawai’i at Manoa, Honolulu, HI, USA
| | - Ahren W. Jasper
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, IL, USA
| | - Alexandre C. R. Gomes
- Centro Federal de Educação Tecnológica de Minas Gerais, CEFET-MG, Minas Gerais, Brazil
| | - Breno R. L. Galvão
- Centro Federal de Educação Tecnológica de Minas Gerais, CEFET-MG, Minas Gerais, Brazil
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7
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Wititsuwannakul T, Hall MB, Gladysz JA. Mechanism of Coupling of Methylidene to Ethylene Ligands in Dimetallic Assemblies; Computational Investigation of a Model for a Key Step in Catalytic C 1 Chemistry. J Am Chem Soc 2022; 144:18672-18687. [PMID: 36174130 DOI: 10.1021/jacs.2c08886] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Methylidene complexes often couple to ethylene complexes, but the mechanistic insight is scant. The path by which two cations [(η5-C5H5)Re(NO)(PPh3)(═CH2)]+ (5+) transform (CH2Cl2/acetonitrile) to [(η5-C5H5)Re(NO)(PPh3)(H2C═CH2)]+ (6+) and [(η5-C5H5)Re(NO)(PPh3)(NCCH3)]+ is studied by density functional theory. Experiments provide a number of constraints such as the second-order rate in 5+; no prior ligand dissociation/exchange; a faster reaction of (S)-5+ with (S)-5+ than with (R)-5+ ("enantiomer self-recognition"). Although dirhenium dications with Re(μ-CH2)2Re cores represent energy minima, they are not accessible by 2 + 2 cycloadditions of 5+. Transition states leading to ReCH2CH2Re linkages are prohibitively high in energy. However, 5+ can give non-covalent SRe/SRe or SRe/RRe dimers with π interactions between the PPh3 ligands but long ReCH2···H2CRe and H2CRe···H2CRe distances (3.073-3.095 Å and 3.878-4.529 Å, respectively). In rate-determining steps, these afford [(η5-C5H5)Re(NO)(PPh3)(μ-η2:η2-H2C···CH2)(Ph3P)(ON)Re(η5-C5H5)]2+ (132+), in which one rhenium binds the bridging ethylene more tightly than the other (2.115-2.098 vs 2.431-2.486 Å to the centroid). In the SRe/RRe adduct, Dewar-Chatt-Duncanson optimization leads to unfavorable PPh3/PPh3 contacts. Ligand interactions are further dissected in the preceding transition states via component analyses, and ΔΔG‡ (1.2 kcal/mol, CH2Cl2) favors the SRe/SRe pathway, in accordance with the experiment. Acetonitrile then displaces 6+ from the more weakly bound rhenium of 132+. The formation of similar μ-H2C···CH2 intermediates is found to be rate-determining for varied coordinatively saturated M═CH2 species [M = Fe(d6)/Re(d4)/Ta(d2)], establishing generality and enhancing relevancy to catalytic CH4 and CO/H2 chemistry.
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Affiliation(s)
- Taveechai Wititsuwannakul
- Department of Chemistry, Texas A&M University, P.O. Box 30012, College Station, Texas 77842-3012, United States
| | - Michael B Hall
- Department of Chemistry, Texas A&M University, P.O. Box 30012, College Station, Texas 77842-3012, United States
| | - John A Gladysz
- Department of Chemistry, Texas A&M University, P.O. Box 30012, College Station, Texas 77842-3012, United States
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8
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Doddipatla S, He C, Goettl SJ, Kaiser RI, Galvão BRL, Millar TJ. Nonadiabatic reaction dynamics to silicon monosulfide (SiS): A key molecular building block to sulfur-rich interstellar grains. SCIENCE ADVANCES 2021; 7:7/26/eabg7003. [PMID: 34172450 PMCID: PMC8232914 DOI: 10.1126/sciadv.abg7003] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Accepted: 05/12/2021] [Indexed: 06/13/2023]
Abstract
Sulfur- and silicon-containing molecules are omnipresent in interstellar and circumstellar environments, but their elementary formation mechanisms have been obscure. These routes are of vital significance in starting a chain of chemical reactions ultimately forming (organo) sulfur molecules-among them precursors to sulfur-bearing amino acids and grains. Here, we expose via laboratory experiments, computations, and astrochemical modeling that the silicon-sulfur chemistry can be initiated through the gas-phase reaction of atomic silicon with hydrogen sulfide leading to silicon monosulfide (SiS) via nonadiabatic reaction dynamics. The facile pathway to the simplest silicon and sulfur diatomic provides compelling evidence for the origin of silicon monosulfide in star-forming regions and aids our understanding of the nonadiabatic reaction dynamics, which control the outcome of the gas-phase formation in deep space, thus expanding our view about the life cycle of sulfur in the galaxy.
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Affiliation(s)
- Srinivas Doddipatla
- Department of Chemistry, University of Hawai'i at Mānoa, Honolulu, HI 96822, USA
| | - Chao He
- Department of Chemistry, University of Hawai'i at Mānoa, Honolulu, HI 96822, USA
| | - Shane J Goettl
- 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.
| | - Breno R L Galvão
- Centro Federal de Educação Tecnológica de Minas Gerais, Av. Amazonas 5253, 30421-169 Belo Horizonte, Brazil.
| | - Tom J Millar
- School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN, Northern Ireland, UK.
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9
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Viegas LP, M. Nunes C, Fausto R. Spin-forbidden heavy-atom tunneling in the ring-closure of triplet cyclopentane-1,3-diyl. Phys Chem Chem Phys 2021; 23:5797-5803. [DOI: 10.1039/d1cp00076d] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The putative spin-forbidden heavy-atom tunneling process for the ring closure of cyclopentane-1,3-diyl at cryogenic temperatures is confirmed with calculations employing the weak-coupling formulation of nonadiabatic transition state theory.
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Affiliation(s)
- Luís P. Viegas
- University of Coimbra
- CQC
- Department of Chemistry
- 3004-535 Coimbra
- Portugal
| | - Cláudio M. Nunes
- University of Coimbra
- CQC
- Department of Chemistry
- 3004-535 Coimbra
- Portugal
| | - Rui Fausto
- University of Coimbra
- CQC
- Department of Chemistry
- 3004-535 Coimbra
- Portugal
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10
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Nunes CM, Viegas LP, Wood SA, Roque JPL, McMahon RJ, Fausto R. Heavy‐Atom Tunneling Through Crossing Potential Energy Surfaces: Cyclization of a Triplet 2‐Formylarylnitrene to a Singlet 2,1‐Benzisoxazole. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202006640] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Cláudio M. Nunes
- University of Coimbra CQC Department of Chemistry 3004-535 Coimbra Portugal
| | - Luís P. Viegas
- University of Coimbra CQC Department of Chemistry 3004-535 Coimbra Portugal
| | - Samuel A. Wood
- Department of Chemistry University of Wisconsin-Madison Madison WI 53706-1322 USA
| | - José P. L. Roque
- University of Coimbra CQC Department of Chemistry 3004-535 Coimbra Portugal
| | - Robert J. McMahon
- Department of Chemistry University of Wisconsin-Madison Madison WI 53706-1322 USA
| | - Rui Fausto
- University of Coimbra CQC Department of Chemistry 3004-535 Coimbra Portugal
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11
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Nunes CM, Viegas LP, Wood SA, Roque JPL, McMahon RJ, Fausto R. Heavy‐Atom Tunneling Through Crossing Potential Energy Surfaces: Cyclization of a Triplet 2‐Formylarylnitrene to a Singlet 2,1‐Benzisoxazole. Angew Chem Int Ed Engl 2020; 59:17622-17627. [PMID: 32558100 DOI: 10.1002/anie.202006640] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Indexed: 11/05/2022]
Affiliation(s)
- Cláudio M. Nunes
- University of Coimbra CQC Department of Chemistry 3004-535 Coimbra Portugal
| | - Luís P. Viegas
- University of Coimbra CQC Department of Chemistry 3004-535 Coimbra Portugal
| | - Samuel A. Wood
- Department of Chemistry University of Wisconsin-Madison Madison WI 53706-1322 USA
| | - José P. L. Roque
- University of Coimbra CQC Department of Chemistry 3004-535 Coimbra Portugal
| | - Robert J. McMahon
- Department of Chemistry University of Wisconsin-Madison Madison WI 53706-1322 USA
| | - Rui Fausto
- University of Coimbra CQC Department of Chemistry 3004-535 Coimbra Portugal
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12
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Han D, Cao H, Zhang F, He M. Quantum chemical study on ·Cl-initiated degradation of ethyl vinyl ether in atmosphere. Mol Phys 2019. [DOI: 10.1080/00268976.2019.1676475] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Affiliation(s)
- Dandan Han
- School of Chemistry and Chemical Engineering, Heze University, Heze, People’s Republic of China
| | - Haijie Cao
- Institute of Materials for Energy and Environment, Qingdao University, Qingdao, People’s Republic of China
| | - Fengrong Zhang
- School of Chemistry and Chemical Engineering, Heze University, Heze, People’s Republic of China
| | - Maoxia He
- Environment Research Institute, Shandong University, Qingdao, People’s Republic of China
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13
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Dabbish E, Ponte F, Russo N, Sicilia E. Antitumor Platinium(IV) Prodrugs: A Systematic Computational Exploration of Their Reduction Mechanism by l-Ascorbic Acid. Inorg Chem 2019; 58:3851-3860. [DOI: 10.1021/acs.inorgchem.8b03486] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Eslam Dabbish
- Department of Chemistry and Chemical Technologies, Università della Calabria, 87036, Arcavacata di Rende, CS, Italy
| | - Fortuna Ponte
- Department of Chemistry and Chemical Technologies, Università della Calabria, 87036, Arcavacata di Rende, CS, Italy
| | - Nino Russo
- Department of Chemistry and Chemical Technologies, Università della Calabria, 87036, Arcavacata di Rende, CS, Italy
| | - Emilia Sicilia
- Department of Chemistry and Chemical Technologies, Università della Calabria, 87036, Arcavacata di Rende, CS, Italy
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14
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Nuñez-Reyes D, Hickson KM. Rate Constants and H-Atom Product Yields for the Reactions of O(1D) Atoms with Ethane and Acetylene from 50 to 296 K. J Phys Chem A 2018; 122:4696-4703. [DOI: 10.1021/acs.jpca.8b02267] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Dianailys Nuñez-Reyes
- Université de Bordeaux, Institut des Sciences Moléculaires, F-33400 Talence, France
- CNRS, Institut des Sciences Moléculaires, F-33400 Talence, France
| | - Kevin M. Hickson
- Université de Bordeaux, Institut des Sciences Moléculaires, F-33400 Talence, France
- CNRS, Institut des Sciences Moléculaires, F-33400 Talence, France
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15
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Lábas A, Menyhárd DK, Harvey JN, Oláh J. First Principles Calculation of the Reaction Rates for Ligand Binding to Myoglobin: The Cases of NO and CO. Chemistry 2018; 24:5350-5358. [PMID: 29285802 DOI: 10.1002/chem.201704867] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2017] [Indexed: 12/12/2022]
Abstract
Ligand binding by proteins is among the most fundamental processes in nature. Among these processes the binding of small gas molecules, such as O2 , CO and NO to heme proteins has traditionally received vivid interest, which was further boosted by their recently recognized significant role in gas sensing in the body. At the heart of the binding of these ligands to the heme group is the spinforbidden reaction between high-spin iron(II) and the ligand yielding a low-spin adduct. We use computational means to address the complete mechanism of CO and NO binding by myoglobin. Considering that it involves several steps occurring on different time scales, molecular dynamics simulations were performed to address the diffusion of the ligand through the enzyme, and DFT calculations in combination with statistical rate calculation to investigate the spin-forbidden reaction. The calculations yielded rate constants in qualitative agreement with experiments and revealed that the bottleneck of NO and CO binding is different; for NO, diffusion was found to be rate-limiting, whereas for CO, the spin-forbidden step is the slowest.
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Affiliation(s)
- Anikó Lábas
- Department of Inorganic Chemistry, Budapest University of Technology and Economics, H-1111, Budapest, Szent Gellért tér 4., Hungary
| | - Dóra K Menyhárd
- MTA-ELTE Protein Modelling Research Group, H-1117, Budapest, Pázmány Péter st. 1/A, Hungary
| | - Jeremy N Harvey
- Department of Chemistry, KU Leuven, B-3001, Leuven Celestijnenlaan 200F- box 2404, Belgium
| | - Julianna Oláh
- Department of Inorganic Chemistry, Budapest University of Technology and Economics, H-1111, Budapest, Szent Gellért tér 4., Hungary
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16
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Shannon R, Glowacki DR. A Simple “Boxed Molecular Kinetics” Approach To Accelerate Rare Events in the Stochastic Kinetic Master Equation. J Phys Chem A 2018; 122:1531-1541. [DOI: 10.1021/acs.jpca.7b12521] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Robin Shannon
- Mechanical Engineering, Stanford University, Stanford, California 94305, United States
- School of Chemistry, University of Bristol, Bristol, BS8 1TS, United Kingdom
| | - David R. Glowacki
- Mechanical Engineering, Stanford University, Stanford, California 94305, United States
- School of Chemistry, University of Bristol, Bristol, BS8 1TS, United Kingdom
- Department of Computer Science, University of Bristol, Bristol, BS8 1UB, United Kingdom
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17
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Motz AR, Herring AM, Vyas S, Maupin CM. Quantum-Mechanical Study of the Reaction Mechanism for 2π-2π Cycloaddition of Fluorinated Methylene Groups. J Org Chem 2017; 82:6578-6585. [PMID: 28548848 DOI: 10.1021/acs.joc.7b00597] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Perfluorocyclobutyl polymers are thermally and chemically stable, may be produced without a catalyst via thermal 2π-2π cycloaddition, and can form block structures, making them suitable for commercialization of specialty polymers. Thermal 2π-2π cycloaddition is a rare reaction that begins in the singlet state and proceeds through a triplet intermediate to form an energetically stable four-membered ring in the singlet state. This reaction involves two changes in spin state and, thus, two spin-crossover transitions. Presented here are density functional theory calculations that evaluate the energetics and reaction mechanisms for the dimerizations of two different polyfluorinated precursors, 1,1,2-trifluoro-2-(trifluoromethoxy)ethane and hexafluoropropylene. The spin-crossover transition states are thoroughly investigated, revealing important kinetics steps and an activation energy for the gas-phase cycloaddition of two hexafluoropropene molecules of 36.9 kcal/mol, which is in good agreement with the experimentally determined value of 34.3 kcal/mol. It is found that the first carbon-carbon bond formation is the rate-limiting step, followed by a rotation about the newly formed bond in the triplet state that results in the formation of the second carbon-carbon bond. Targeting the rotation of the C-C bond, a set of parameters were obtained that best produce high molecular weight polymers using this chemistry.
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Affiliation(s)
- Andrew R Motz
- Department of Chemical & Biological Engineering, Colorado School of Mines , Golden, Colorado 80401, United States
| | - Andrew M Herring
- Department of Chemical & Biological Engineering, Colorado School of Mines , Golden, Colorado 80401, United States
| | - Shubham Vyas
- Department of Chemistry, Colorado School of Mines , Golden, Colorado 80401, United States
| | - C Mark Maupin
- Department of Chemical & Biological Engineering, Colorado School of Mines , Golden, Colorado 80401, United States
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18
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Sicilia E, Mazzone G, Pérez-González A, Pirillo J, Galano A, Heine T, Russo N. Direct and cluster-assisted dehydrogenation of methane by Nb + and Ta +: a theoretical investigation. Phys Chem Chem Phys 2017; 19:16178-16188. [PMID: 28604858 DOI: 10.1039/c7cp01833a] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
DFT calculations have been performed to examine both direct and cluster-assisted methane C-H bond activation by Nb+ and Ta+ cations. The commonly accepted dehydrogenation pathways, that are oxidative addition and reductive elimination, have been studied in detail for methane ligated clusters M(CH4)n+ (M = Nb, Ta and n = 1-4). For the second H atom transfer to the metal in the presence of additional CH4 molecules (n > 1) two alternative routes have been explored. Energy profiles for ground quintet and excited triplet and singlet spin states of both Nb+ and Ta+ cations have been calculated. Spin crossings occur for all the examined pathways. Clustering of methane ligands appears to favorably affect the process stabilizing all the intercepted minima and transition states and bringing all the calculated PESs below the reference energy of the separated reactants. The direct activation of methane (n = 1) can proceed efficiently only for Ta+, whereas dehydrogenation is endothermic for Nb+ by 9.0 kcal mol-1. When assisted by additional methane ligands, the dehydrogenation process becomes exothermic for both cations whatever the number of coordinated molecules.
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Affiliation(s)
- Emilia Sicilia
- Department Of Chemistry and Chemical Technologies, University of Calabria, Via P. Bucci, I-87036 Arcavacata di Rende, Italy.
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19
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Nuñez-Reyes D, Hickson KM. Kinetic and Product Study of the Reactions of C(1D) with CH4 and C2H6 at Low Temperature. J Phys Chem A 2017; 121:3851-3857. [DOI: 10.1021/acs.jpca.7b01790] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Dianailys Nuñez-Reyes
- Université de Bordeaux, Institut des Sciences Moléculaires, F-33400 Talence, France
- CNRS, Institut des Sciences Moléculaires, F-33400 Talence, France
| | - Kevin M. Hickson
- Université de Bordeaux, Institut des Sciences Moléculaires, F-33400 Talence, France
- CNRS, Institut des Sciences Moléculaires, F-33400 Talence, France
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20
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Fong A, Peters B, Scott SL. One-Electron-Redox Activation of the Reduced Phillips Polymerization Catalyst, via Alkylchromium(IV) Homolysis: A Computational Assessment. ACS Catal 2016. [DOI: 10.1021/acscatal.6b01728] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Anthony Fong
- Department
of Chemical Engineering, University of California, Santa Barbara, California 93106-5080, United States
| | - Baron Peters
- Department
of Chemical Engineering, University of California, Santa Barbara, California 93106-5080, United States
- Department of Chemistry & Biochemistry, University of California, Santa Barbara, California 93106-9510, United States
| | - Susannah L. Scott
- Department
of Chemical Engineering, University of California, Santa Barbara, California 93106-5080, United States
- Department of Chemistry & Biochemistry, University of California, Santa Barbara, California 93106-9510, United States
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21
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Li M, Cao H, Han D, Li X, He M. Kinetics and mechanism of the reactions of OH radicals with p-nitroaniline in gas-phase and aqueous solution. COMPUT THEOR CHEM 2015. [DOI: 10.1016/j.comptc.2014.12.028] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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22
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Han D, Cao H, Li M, Li X, Zhang S, He M, Hu J. Computational Study on the Mechanisms and Rate Constants of the Cl-Initiated Oxidation of Methyl Vinyl Ether in the Atmosphere. J Phys Chem A 2015; 119:719-27. [DOI: 10.1021/jp5112839] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Dandan Han
- Environment Research
Institute, Shandong University, Jinan 250100, People’s Republic of China
| | - Haijie Cao
- Environment Research
Institute, Shandong University, Jinan 250100, People’s Republic of China
| | - Mingyue Li
- Environment Research
Institute, Shandong University, Jinan 250100, People’s Republic of China
| | - Xin Li
- Environment Research
Institute, Shandong University, Jinan 250100, People’s Republic of China
| | - Shiqing Zhang
- Environment Research
Institute, Shandong University, Jinan 250100, People’s Republic of China
| | - Maoxia He
- Environment Research
Institute, Shandong University, Jinan 250100, People’s Republic of China
| | - Jingtian Hu
- Environment Research
Institute, Shandong University, Jinan 250100, People’s Republic of China
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23
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Theoretical studies on the mechanisms and rate constants for the hydroxylation of n-butyl, iso-butyl and tert-butyl vinyl ethers in atmosphere. Struct Chem 2014. [DOI: 10.1007/s11224-014-0517-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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24
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Liu S, Srinivasan S, Tao J, Grady MC, Soroush M, Rappe AM. Modeling spin-forbidden monomer self-initiation reactions in spontaneous free-radical polymerization of acrylates and methacrylates. J Phys Chem A 2014; 118:9310-8. [PMID: 25188223 DOI: 10.1021/jp503794j] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A spin-forbidden reaction is a reaction in which the total electronic spin-state changes. The standard transition-state theory that assumes a reaction occurs on a single potential energy surface with spin-conservation cannot be applied to a spin-forbidden reaction directly. In this work, we derive the crossing coefficient based on the Wentzel-Kramers-Brillouin (WKB) theory to quantify the effect of intersystem crossing on the kinetics of spin-forbidden reactions. Acrylates and methacrylates, by themselves, can generate free radicals that initiate polymerization at temperatures above 120 °C. Previous studies suggest that a triplet diradical is a key intermediate in the self-initiation. The formation of a triplet diradical from two closed-shell monomer molecules is a spin-forbidden reaction. This study provides a quantitative analysis of singlet-triplet spin crossover of diradical species in self-initiation of acrylates and methacrylates, taking into account the effect of intersystem crossing. The concept of crossing control is introduced and demonstrated computationally to be a new likely route to generate monoradicals via monomer self-initiation in high temperature polymerization.
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Affiliation(s)
- Shi Liu
- The Makineni Theoretical Laboratories, Department of Chemistry, University of Pennsylvania , Philadelphia, Pennsylvania 19104-6323, United States
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25
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Han D, Cao H, Li J, Li M, He M, Hu J. Computational study on the mechanisms and rate constants of the OH-initiated oxidation of ethyl vinyl ether in atmosphere. CHEMOSPHERE 2014; 111:61-69. [PMID: 24997901 DOI: 10.1016/j.chemosphere.2014.03.045] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Revised: 02/23/2014] [Accepted: 03/07/2014] [Indexed: 06/03/2023]
Abstract
The hydroxylation reactions of ethyl vinyl ether (EVE) in the present of O2 and NO are analyzed by using MPWB1K/6-311++G(3df,2p)//MPWB1K/6-31+G(d,p) level of theory. According to the calculated thermodynamic data, the detailed reaction mechanisms of EVE and OH are proposed. All of the ten possible reaction pathways are discussed. The major products of the title reaction are ethyl formate and formaldehyde, which is in accordance with experimental detection. The rate constants of the primary reactions over the temperature of 250-400K and the pressure range of 100-2000Torr are computed by employing MESMER program. At 298K and 760Torr, OH-addition channels are predominate and the total rate constant is ktot=4.53×10(-11)cm(3)molecule(-1)s(-1). The Arrhenius equation is obtained as ktot=6.27×10(-12)exp(611.5/T), according to the rate constants given at different temperatures. Finally, the atmospheric half life of EVE with respect to OH is estimated to be 2.13h.
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Affiliation(s)
- Dandan Han
- Environment Research Institute, Shandong University, Jinan 250100, PR China
| | - Haijie Cao
- Environment Research Institute, Shandong University, Jinan 250100, PR China
| | - Jing Li
- Environment Research Institute, Shandong University, Jinan 250100, PR China
| | - Mingyue Li
- Environment Research Institute, Shandong University, Jinan 250100, PR China
| | - Maoxia He
- Environment Research Institute, Shandong University, Jinan 250100, PR China.
| | - Jingtian Hu
- Environment Research Institute, Shandong University, Jinan 250100, PR China
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26
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Polino D, Klippenstein SJ, Harding LB, Georgievskii Y. Predictive Theory for the Addition and Insertion Kinetics of 1CH2 Reacting with Unsaturated Hydrocarbons. J Phys Chem A 2013; 117:12677-92. [DOI: 10.1021/jp406246y] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Daniela Polino
- Chemical
Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
- Dipartimento
di Chimica, Materiali e Ingegneria chimica “G. Natta”, Politecnico di Milano, via Mancinelli 7, 20131 Milano, Italy
| | - Stephen J. Klippenstein
- Chemical
Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Lawrence B. Harding
- Chemical
Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Yuri Georgievskii
- Chemical
Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
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27
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Cao H, He M, Han D, Li J, Li M, Wang W, Yao S. OH-initiated oxidation mechanisms and kinetics of 2,4,4'-Tribrominated diphenyl ether. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2013; 47:8238-8247. [PMID: 23855483 DOI: 10.1021/es400088v] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
2,4,4'-Tribromodiphenyl ether (BDE-28) was selected as a typical congener of polybrominated diphenyl ethers (PBDEs) to examine its fate both in the atmosphere and in water solution. All the calculations were obtained at the ground state. The mechanism result shows that the oxidations between BDE-28 and OH radicals are highly feasible especially at the less-brominated phenyl ring. Hydroxylated dibrominated diphenyl ethers (OH-PBDEs) are formed through direct bromine-substitution reactions (P1∼P3) or secondary reactions of OH-adducts (P4∼P8). Polybrominated dibenzo-p-dioxins (PBDDs) resulting from o-OH-PBDEs are favored products compared with polybrominated dibenzofurans (PBDFs) generated by bromophenols and their radicals. The complete degradation of OH adducts in the presence of O2/NO, which generates unsaturated ketones and aldehydes, is less feasible compared with the H-abstraction pathways by O2. Aqueous solution reduces the feasibility between BDE-28 and the OH radical. The rate constant of BDE-28 and the OH radical is determined to be 1.79 × 10(-12) cm(3) molecule(-1) s(-1) with an atmospheric lifetime of 6.7 days.
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Affiliation(s)
- Haijie Cao
- Environment Research Institute, Shandong University, Jinan 250100, PR China
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28
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29
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Glowacki DR, Liang CH, Morley C, Pilling MJ, Robertson SH. MESMER: An Open-Source Master Equation Solver for Multi-Energy Well Reactions. J Phys Chem A 2012; 116:9545-60. [DOI: 10.1021/jp3051033] [Citation(s) in RCA: 397] [Impact Index Per Article: 33.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | - Chi-Hsiu Liang
- School of Chemistry, University of Leeds, Leeds LS2 9JT,
U.K
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30
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Plane JMC, Whalley CL, Frances-Soriano L, Goddard A, Harvey JN, Glowacki DR, Viggiano AA. O2(a1Δg) + Mg, Fe, and Ca: Experimental kinetics and formulation of a weak collision, multiwell master equation with spin-hopping. J Chem Phys 2012; 137:014310. [DOI: 10.1063/1.4730423] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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31
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Blitz MA, Seakins PW. Laboratory studies of photochemistry and gas phase radical reaction kinetics relevant to planetary atmospheres. Chem Soc Rev 2012; 41:6318-47. [DOI: 10.1039/c2cs35204d] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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32
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Blitz MA, Kappler C, Pilling MJ, Seakins PW. 3CH2 + O2: Kinetics and Product Channel Branching Ratios. ACTA ACUST UNITED AC 2011. [DOI: 10.1524/zpch.2011.0138] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Abstract
The kinetics of and the yield of OH in the reaction 3CH2 + O2 has been studied at room temperature using pulsed laser photolysis of ketene at 351 nm with detection of OH by LIF. The kinetics were determined from a biexponential analysis of the growth and decay of the OH signal. The rate coefficients obtained from the profiles for OH(v=0,1) are (2.39 ± 0.26) and (2.33 ± 0.28) × 1012 cm3 molecule−1 s−1 respectively. The rate coefficient for 3CH2 + NO was also measured from the growth of the OH(v=1) signal, giving k
3 = (4.52 ± 0.48) × 1011 cm3 molecule−1 s−1. The ratio of the yields of OH in the two reactions 3CH2+O2 and 3CH 2+NO was determined from analysis of back to back OH profiles with O2 and NO as co-reactant; the ratio obtained, at 300 K, was 2.96 ± 0.14. This result was combined with other experimental product yields on these two reactions to obtain a consistent set channel yields for 3CH2+O2 and 3CH2+NO at ∼300 K.
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Affiliation(s)
| | - Claudia Kappler
- University of Leeds, School of Chemistry, LS2 9JT, Leeds, Großbritannien
| | - Michael J. Pilling
- University of Leeds, School of Chemistry, Leeds, LS2 9JT, Großbritannien
| | - Paul W. Seakins
- University of Leeds, School of Chemistry, LS2 9JT, Leeds, Großbritannien
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33
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Gannon KL, Blitz MA, Liang CH, Pilling MJ, Seakins PW, Glowacki DR. Temperature Dependent Kinetics (195−798 K) and H Atom Yields (298−498 K) from Reactions of 1CH2 with Acetylene, Ethene, and Propene. J Phys Chem A 2010; 114:9413-24. [DOI: 10.1021/jp102276j] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- K. L. Gannon
- School of Chemistry, University of Leeds, Leeds, LS2 9JT, United Kingdom
| | - M. A. Blitz
- School of Chemistry, University of Leeds, Leeds, LS2 9JT, United Kingdom
| | - C. H. Liang
- School of Chemistry, University of Leeds, Leeds, LS2 9JT, United Kingdom
| | - M. J. Pilling
- School of Chemistry, University of Leeds, Leeds, LS2 9JT, United Kingdom
| | - P. W. Seakins
- School of Chemistry, University of Leeds, Leeds, LS2 9JT, United Kingdom
| | - D. R. Glowacki
- School of Chemistry, University of Leeds, Leeds, LS2 9JT, U.K., and School of Chemistry, Centre for Computational Chemistry, University of Bristol, Bristol, BS8 1TS, United Kingdom
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