1
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Theoretical study about the hydrogen abstraction reactions on methyl acetate on combustion conditions. J Mol Model 2022; 28:226. [DOI: 10.1007/s00894-022-05227-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Accepted: 07/08/2022] [Indexed: 11/26/2022]
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2
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Li W, Li J, Ning H, Shang Y, Luo SN. Multistructural Variational Reaction Kinetics of the Simplest Unsaturated Methyl Ester: H-Abstraction from Methyl Acrylate by H, OH, CH 3, and HO 2 Radicals. J Phys Chem A 2021; 125:5103-5116. [PMID: 34082530 DOI: 10.1021/acs.jpca.1c01788] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The H-abstraction reaction kinetics of methyl acrylate (MA) + H/OH/CH3/HO2 radicals have been investigated theoretically in the present work. For these reactions, the reaction energies and barrier heights are first computed using several density functionals and compared to the coupled cluster CCSD(T)-F12/jun-cc-pVTZ benchmark calculations. The M062X/maug-cc-pVTZ method shows the best performance with the smallest mean unsigned deviation (MUD) of 0.42 kcal mol-1. Combined with the electronic structure calculations using the M062X/maug-cc-pVTZ method, the multistructural canonical variational transition-state theory (MS-CVT) with small-curvature tunneling (SCT) is employed to calculate the reaction rate constants at 500-2000 K. The variational effect is between 0.56 and 1.0, the multistructural torsional anharmonicity factor ranges from 0.004 to 4.57, and the tunneling coefficient is in the range of 0.5-4.70. Notably, given the existence of reactant complexes (RCs) between reactants and transition states for the reaction systems MA + OH/HO2, we further compare the rate constants under the low-pressure limit (LPL) kinetic model, which treats the reaction as a single-step process and neglects RCs, and the pre-equilibrium model, which takes RCs into account in the reaction and treats the reaction as a two-step process. The rate constants calculated by these two models are similar within the combustion temperature range, and apparent differences occur at lower temperatures. In addition, we determine the branching ratios as a function of temperature and find that the methyl site (S3) abstractions by OH and H radicals are dominant in the low- and high-temperature ranges, respectively. Moreover, we update the kinetic model with the calculated H-abstraction rate constants to simulate the ignition delay times of MA. The simulations of the updated model are in good agreement with experimental results. The accurate reaction kinetics determined in this work are useful for the understanding and prediction of consumption branching fractions and ignition properties of the unsaturated methyl esters.
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Affiliation(s)
- Wenrui Li
- School of Chemistry and Chemical Engineering & Chongqing Key Laboratory of Theoretical and Computational Chemistry, Chongqing University, Chongqing 401331, China.,Key Laboratory of Advanced Technologies of Materials, Ministry of Education, Southwest Jiaotong University, Chengdu, Sichuan 610031, China
| | - Jun Li
- School of Chemistry and Chemical Engineering & Chongqing Key Laboratory of Theoretical and Computational Chemistry, Chongqing University, Chongqing 401331, China
| | - Hongbo Ning
- Key Laboratory of Advanced Technologies of Materials, Ministry of Education, Southwest Jiaotong University, Chengdu, Sichuan 610031, China
| | - Yanlei Shang
- Key Laboratory of Advanced Technologies of Materials, Ministry of Education, Southwest Jiaotong University, Chengdu, Sichuan 610031, China
| | - Sheng-Nian Luo
- Key Laboratory of Advanced Technologies of Materials, Ministry of Education, Southwest Jiaotong University, Chengdu, Sichuan 610031, China
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3
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Viegas LP. Simplified Protocol for the Calculation of Multiconformer Transition State Theory Rate Constants Applied to Tropospheric OH-Initiated Oxidation Reactions. J Phys Chem A 2021; 125:4499-4512. [PMID: 33902279 DOI: 10.1021/acs.jpca.1c00683] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Chemical kinetics plays a fundamental role in the understanding and modeling of tropospheric chemical processes, one of the most important being the atmospheric degradation of volatile organic compounds. These potentially harmful molecules are emitted into the troposphere by natural and anthropogenic sources and are chemically removed by undergoing oxidation processes, most frequently initiated by reaction with OH radicals, the atmosphere's "detergent". Obtaining the respective rate constants is therefore of critical importance, with calculations based on transition state theory (TST) often being the preferred choice. However, for molecules with rich conformational variety, a single-conformer method such as lowest-conformer TST is unsuitable while state-of-the-art TST-based methodologies easily become unmanageable. In this Feature Article, the author reviews his own cost-effective protocol for the calculation of bimolecular rate constants of OH-initiated reactions in the high-pressure limit based on multiconformer transition state theory. The protocol, which is easily extendable to other oxidation reactions involving saturated organic molecules, is based on a variety of freeware and open-source software and tested against a series of oxidation reactions of hydrofluoropolyethers, computationally very challenging molecules with potential environmental relevance. The main features, advantages and disadvantages of the protocol are presented, along with an assessment of its predictive utility based on a comparison with experimental rate constants.
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Affiliation(s)
- Luís P Viegas
- Aarhus Institute of Advanced Studies, Aarhus University, Høegh-Guldbergs Gade 6B, Buildings 1630-1632, Aarhus 8000, Denmark
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4
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Meng Q, Zhang L, Chen Q, Chi Y, Zhang P. Influence of Torsional Anharmonicity on the Reactions of Methyl Butanoate with Hydroperoxyl Radical. J Phys Chem A 2020; 124:8643-8652. [PMID: 32986416 DOI: 10.1021/acs.jpca.0c05466] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
An ab initio chemical kinetics study of the reactions of methyl butanoate (MB) with hydroperoxyl radical (HO2) is presented in this paper. Particular interest is placed on determining the influences of torsional anharmonicity and addition reaction on the rate constants of hydrogen abstraction reactions. Stationary points on the potential energy surface of MB + HO2 are calculated at the level of QCISD(T)/CBS//B3LYP/6-311++G(d,p). The transition state theory (TST) is used to calculate the high-pressure limit rate constants of the hydrogen abstraction reactions over a board range of temperature (500-2000 K). Anharmonicity of low-frequency torsional modes is considered in the rate calculations by using the one-dimensional hindered rotor approximation and the internal-coordinate multistructural approximation; the latter is used as a higher-level theoretical method to examine the applicability of the former in dealing with strongly coupled torsional modes. The calculated rate constants are compared with the available data from the literature and observed discrepancies are analyzed in detail. An energetically lowest-lying addition reaction with subsequent isomerization and decomposition reactions are identified on the potential energy surface. The multiple-well Master equation analysis shows that these reactions have a secondary influence on the rate constants in the temperature range of interest.
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Affiliation(s)
- Qinghui Meng
- Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong.,National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029, Anhui, P.R. China
| | - Lidong Zhang
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029, Anhui, P.R. China
| | - Qinxue Chen
- Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong
| | - Yicheng Chi
- Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong
| | - Peng Zhang
- Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong
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5
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Viegas LSP, Jensen F. Reactivity of α,ω-Dihydrofluoropolyethers toward OH Predicted by Multiconformer Transition State Theory and the Interacting Quantum Atoms Approach. J Phys Chem A 2020; 124:3460-3470. [PMID: 32242667 DOI: 10.1021/acs.jpca.0c02911] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We report rate constants for the tropospheric reaction between the OH radical and α,ω-dihydrofluoropolyethers, which represent a specific class of the hydrofluoropolyethers family with the formula HF2C(OCF2CF2)p(OCF2)qOCF2H. Four cases were considered: p0q2, p0q3, p1q0, and p1q1 (pxqy denoting p = x and q = y) with the calculations performed by a cost-effective protocol developed for bimolecular hydrogen-abstraction reactions. This protocol is based on multiconformer transition state theory and relies on computationally accessible M08-HX/apcseg-2//M08-HX/pcseg-1 calculations. Within the protocol's approximations, the results show that (1) the calculated rate constants are within a factor of five of the experimental results (p1q0 and p1q1) and (2) the chain length and composition have a negligible effect on the rate constants, which is consistent with the experimental work. The interacting quantum atoms energy decomposition scheme is used to analyze the observed trends and extract chemical information related to the imaginary frequencies and barrier heights that are key parameters controlling the reactivity of the reaction. The intramolecular exchange-correlation contributions in the reactants and transition states were found to be the dominating factor.
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Affiliation(s)
- Luı S P Viegas
- Aarhus Institute of Advanced Studies, Aarhus University, Høegh-Guldbergs Gade 6B, Buildings 1630-1632, Aarhus 8000, Denmark
| | - Frank Jensen
- Department of Chemistry, Aarhus University, 8000 Aarhus C, Denmark
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6
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Viegas LP. Theoretical determination of the OH-initiated oxidation rate constants of $${\alpha ,\omega }$$-dialkoxyfluoropolyethers. Theor Chem Acc 2019. [DOI: 10.1007/s00214-019-2436-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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7
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Xing L, Bao JL, Wang Z, Wang X, Truhlar DG. Relative Rates of Hydrogen Shift Isomerizations Depend Strongly on Multiple-Structure Anharmonicity. J Am Chem Soc 2018; 140:17556-17570. [DOI: 10.1021/jacs.8b09381] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Lili Xing
- Energy and Power Engineering Institute, Henan University of Science and Technology, Luoyang, Henan 471003, China
| | - Junwei Lucas Bao
- Department of Chemistry, Chemical Theory Center, and Minnesota Supercomputing Institute, University of Minnesota, Minnesota 55455-0431, United States
| | - Zhandong Wang
- Clean Combustion Research Center, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
| | - Xuetao Wang
- Energy and Power Engineering Institute, Henan University of Science and Technology, Luoyang, Henan 471003, China
| | - Donald G. Truhlar
- Department of Chemistry, Chemical Theory Center, and Minnesota Supercomputing Institute, University of Minnesota, Minnesota 55455-0431, United States
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8
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Firaha DS, Döntgen M, Berkels B, Leonhard K. Pressure-Dependent Rate Constant Predictions Utilizing the Inverse Laplace Transform: A Victim of Deficient Input Data. ACS OMEGA 2018; 3:8212-8219. [PMID: 31458958 PMCID: PMC6644344 DOI: 10.1021/acsomega.8b00311] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/21/2018] [Accepted: 06/07/2018] [Indexed: 06/10/2023]
Abstract
k(E) can be calculated either from the Rice-Ramsperger-Kassel-Marcus theory or by inverting macroscopic rate constants k(T). Here, we elaborate the inverse Laplace transform approach for k(E) reconstruction by examining the impact of k(T) data fitting accuracy. For this approach, any inaccuracy in the reconstructed k(E) results from inaccurate/incomplete k(T) description. Therefore, we demonstrate how an improved mathematical description of k(T) data leads to accurate k(E) data. Refitting inaccurate/incomplete k(T), hence, allows for recapturing k(T) information that yields more accurate k(E) reconstructions. The present work suggests that accurate representation of experimental and theoretical k(T) data in a broad temperature range could be used to obtain k(T,p). Thus, purely temperature-dependent kinetic models could be converted into fully temperature- and pressure-dependent kinetic models.
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Affiliation(s)
- Dzmitry S. Firaha
- AICES
Graduate School, Rheinisch-Westfälische
Technische Hochschule Aachen, Schinkelstr. 2, D-52062 Aachen, Germany
- Chair
of Technical Thermodynamics, Rheinisch-Westfälische
Technische Hochschule Aachen, Schinkelstr. 8, D-52062 Aachen, Germany
| | - Malte Döntgen
- Chair
of Technical Thermodynamics, Rheinisch-Westfälische
Technische Hochschule Aachen, Schinkelstr. 8, D-52062 Aachen, Germany
| | - Benjamin Berkels
- AICES
Graduate School, Rheinisch-Westfälische
Technische Hochschule Aachen, Schinkelstr. 2, D-52062 Aachen, Germany
| | - Kai Leonhard
- AICES
Graduate School, Rheinisch-Westfälische
Technische Hochschule Aachen, Schinkelstr. 2, D-52062 Aachen, Germany
- Chair
of Technical Thermodynamics, Rheinisch-Westfälische
Technische Hochschule Aachen, Schinkelstr. 8, D-52062 Aachen, Germany
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9
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Massie AA, Sinha A, Parham JD, Nordlander E, Jackson TA. Relationship between Hydrogen-Atom Transfer Driving Force and Reaction Rates for an Oxomanganese(IV) Adduct. Inorg Chem 2018; 57:8253-8263. [PMID: 29974738 DOI: 10.1021/acs.inorgchem.8b00852] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Hydrogen atom transfer (HAT) reactions by high-valent metal-oxo intermediates are important in both biological and synthetic systems. While the HAT reactivity of FeIV-oxo adducts has been extensively investigated, studies of analogous MnIV-oxo systems are less common. There are several recent reports of MnIV-oxo complexes, supported by neutral pentadentate ligands, capable of cleaving strong C-H bonds at rates approaching those of analogous FeIV-oxo species. In this study, we provide a thorough analysis of the HAT reactivity of one of these MnIV-oxo complexes, [MnIV(O)(2pyN2Q)]2+, which is supported by an N5 ligand with equatorial pyridine and quinoline donors. This complex is able to oxidize the strong C-H bonds of cyclohexane with rates exceeding those of FeIV-oxo complexes with similar ligands. In the presence of excess oxidant (iodosobenzene), cyclohexane oxidation by [MnIV(O)(2pyN2Q)]2+ is catalytic, albeit with modest turnover numbers. Because the rate of cyclohexane oxidation by [MnIV(O)(2pyN2Q)]2+ was faster than that predicted by a previously published Bells-Evans-Polanyi correlation, we expanded the scope of this relationship by determining HAT reaction rates for substrates with bond dissociation energies spanning 20 kcal/mol. This extensive analysis showed the expected correlation between reaction rate and the strength of the substrate C-H bond, albeit with a shallow slope. The implications of this result with regard to MnIV-oxo and FeIV-oxo reactivity are discussed.
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Affiliation(s)
- Allyssa A Massie
- The University of Kansas , Chemistry Department , 1251 Wescoe Hall Drive , Lawrence , Kansas 66045 , United States
| | - Arup Sinha
- Lund University , Chemical Physics, Department of Chemistry , Box 124, SE-221 00 Lund , Sweden
| | - Joshua D Parham
- The University of Kansas , Chemistry Department , 1251 Wescoe Hall Drive , Lawrence , Kansas 66045 , United States
| | - Ebbe Nordlander
- Lund University , Chemical Physics, Department of Chemistry , Box 124, SE-221 00 Lund , Sweden
| | - Timothy A Jackson
- The University of Kansas , Chemistry Department , 1251 Wescoe Hall Drive , Lawrence , Kansas 66045 , United States
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10
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Sanches-Neto FO, Coutinho ND, Carvalho-Silva VH. A novel assessment of the role of the methyl radical and water formation channel in the CH 3OH + H reaction. Phys Chem Chem Phys 2018; 19:24467-24477. [PMID: 28890979 DOI: 10.1039/c7cp03806b] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A number of experimental and theoretical papers accounted almost exclusively for two channels in the reaction of atomic hydrogen with methanol: H-abstraction from the methyl (R1) and hydroxyl (R2) functional groups. Recently, several astrochemical studies claimed the importance of another channel for this reaction, which is crucial for kinetic simulations related to the abundance of molecular constituents in planetary atmospheres: methyl radical and water formation (R3 channel). Here, motivated by the lack of and uncertainties about the experimental and theoretical kinetic rate constants for the third channel, we developed first-principles Car-Parrinello molecular dynamics thermalized at two significant temperatures - 300 and 2500 K. Furthermore, the kinetic rate constant of all three channels was calculated using a high-level deformed-transition state theory (d-TST) at a benchmark electronic structure level. d-TST is shown to be suitable for describing the overall rate constant for the CH3OH + H reaction (an archetype of the moderate tunnelling regime) with the precision required for practical applications. Considering the experimental ratios at 1000 K, kR1/kR2 ≈ 0.84 and kR1/kR3 ≈ 15-40, we provided a better estimate when compared with previous theoretical work: 7.47 and 637, respectively. The combination of these procedures explicitly demonstrates the role of the third channel in a significant range of temperatures and indicates its importance considering the thermodynamic control to estimate methyl radical and water formation. We expect that these results can help to shed new light on the fundamental kinetic rate equations for the CH3OH + H reaction.
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Affiliation(s)
- Flávio O Sanches-Neto
- Grupo de Química Teórica de Anápolis Campus de Ciências Exatas e Tecnológicas, Universidade Estadual de Goiás, Caixa Postal 459, 75001-970, Anápolis, GO, Brazil.
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11
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Bao JL, Zhang X, Truhlar DG. Predicting pressure-dependent unimolecular rate constants using variational transition state theory with multidimensional tunneling combined with system-specific quantum RRK theory: a definitive test for fluoroform dissociation. Phys Chem Chem Phys 2018; 18:16659-70. [PMID: 27273734 DOI: 10.1039/c6cp02765b] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Understanding the falloff in rate constants of gas-phase unimolecular reaction rate constants as the pressure is lowered is a fundamental problem in chemical kinetics, with practical importance for combustion, atmospheric chemistry, and essentially all gas-phase reaction mechanisms. In the present work, we use our recently developed system-specific quantum RRK theory, calibrated by canonical variational transition state theory with small-curvature tunneling, combined with the Lindemann-Hinshelwood mechanism, to model the dissociation reaction of fluoroform (CHF3), which provides a definitive test for falloff modeling. Our predicted pressure-dependent thermal rate constants are in excellent agreement with experimental values over a wide range of pressures and temperatures. The present validation of our methodology, which is able to include variational transition state effects, multidimensional tunneling based on the directly calculated potential energy surface along the tunneling path, and torsional and other vibrational anharmonicity, together with state-of-the-art reaction-path-based direct dynamics calculations, is important because the method is less empirical than models routinely used for generating full mechanisms, while also being simpler in key respects than full master equation treatments and the full reduced falloff curve and modified strong collision methods of Troe.
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Affiliation(s)
- Junwei Lucas Bao
- Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, USA.
| | - Xin Zhang
- State Key Laboratory of Chemical Resource Engineering, Institute of Materia Medica, College of Science, Beijing University of Chemical Technology, Beijing, 100029, P. R. China. and Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, USA.
| | - Donald G Truhlar
- Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, USA.
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12
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Klein JEMN, Dereli B, Que L, Cramer CJ. Why metal-oxos react with dihydroanthracene and cyclohexadiene at comparable rates, despite having different C-H bond strengths. A computational study. Chem Commun (Camb) 2018; 52:10509-12. [PMID: 27489080 DOI: 10.1039/c6cc05395e] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
1,4-Cyclohexadiene (CHD) and 9,10-dihydroanthracene (DHA) are two substrates used to probe the steric requirements of metal-oxo oxidants in H-atom-transfer (HAT) reactions, based on the assumption that they have comparable C-H bond dissociation enthalpies (BDEs). We use computations to demonstrate that the BDE of DHA is ∼3.5 kcal mol(-1) larger than that of CHD and that their often comparable reactivity is based on a competing interplay of bond strengths and favorable van der Waals interactions.
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Affiliation(s)
- Johannes E M N Klein
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant St. S.E., Minneapolis, Minnesota 55455, USA.
| | - Büsra Dereli
- Department of Chemistry, Supercomputing Institute, and Chemical Theory Center, University of Minnesota, 207 Pleasant Street S.E., Minneapolis, Minnesota 55455, USA
| | - Lawrence Que
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant St. S.E., Minneapolis, Minnesota 55455, USA.
| | - Christopher J Cramer
- Department of Chemistry, Supercomputing Institute, and Chemical Theory Center, University of Minnesota, 207 Pleasant Street S.E., Minneapolis, Minnesota 55455, USA
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13
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Li X, You X, Law CK, Truhlar DG. Kinetics and branching fractions of the hydrogen abstraction reaction from methyl butenoates by H atoms. Phys Chem Chem Phys 2017; 19:16563-16575. [DOI: 10.1039/c7cp01686g] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We studied hydrogen abstraction reactions at various sites of unsaturated methyl esters by H atoms, including variational effects, tunneling and multi-structural torsional anharmonicity.
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Affiliation(s)
- Xiaoyu Li
- Center for Combustion Energy
- Tsinghua University
- Beijing
- China
- Key Laboratory for Thermal Science and Power Engineering of Ministry of Education
| | - Xiaoqing You
- Center for Combustion Energy
- Tsinghua University
- Beijing
- China
- Key Laboratory for Thermal Science and Power Engineering of Ministry of Education
| | - Chung K. Law
- Center for Combustion Energy
- Tsinghua University
- Beijing
- China
- Department of Mechanical and Aerospace Engineering
| | - Donald G. Truhlar
- Department of Chemistry
- Chemical Theory Center, and Minnesota Supercomputing Institute
- University of Minnesota
- Minneapolis
- USA
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14
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Bao JL, Truhlar DG. Variational transition state theory: theoretical framework and recent developments. Chem Soc Rev 2017; 46:7548-7596. [DOI: 10.1039/c7cs00602k] [Citation(s) in RCA: 207] [Impact Index Per Article: 29.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
This article reviews the fundamentals of variational transition state theory (VTST), its recent theoretical development, and some modern applications.
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Affiliation(s)
- Junwei Lucas Bao
- Department of Chemistry
- Chemical Theory Center, and Minnesota Supercomputing Institute
- University of Minnesota
- Minneapolis
- USA
| | - Donald G. Truhlar
- Department of Chemistry
- Chemical Theory Center, and Minnesota Supercomputing Institute
- University of Minnesota
- Minneapolis
- USA
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15
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Bao JL, Zheng J, Truhlar DG. Kinetics of Hydrogen Radical Reactions with Toluene Including Chemical Activation Theory Employing System-Specific Quantum RRK Theory Calibrated by Variational Transition State Theory. J Am Chem Soc 2016; 138:2690-704. [PMID: 26841076 DOI: 10.1021/jacs.5b11938] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Pressure-dependent reactions are ubiquitous in combustion and atmospheric chemistry. We employ a new calibration procedure for quantum Rice-Ramsperger-Kassel (QRRK) unimolecular rate theory within a chemical activation mechanism to calculate the pressure-falloff effect of a radical association with an aromatic ring. The new theoretical framework is applied to the reaction of H with toluene, which is a prototypical reaction in the combustion chemistry of aromatic hydrocarbons present in most fuels. Both the hydrogen abstraction reactions and the hydrogen addition reactions are calculated. Our system-specific (SS) QRRK approach is adjusted with SS parameters to agree with multistructural canonical variational transition state theory with multidimensional tunneling (MS-CVT/SCT) at the high-pressure limit. The new method avoids the need for the usual empirical estimations of the QRRK parameters, and it eliminates the need for variational transition state theory calculations as a function of energy, although in this first application we do validate the falloff curves by comparing SS-QRRK results without tunneling to multistructural microcanonical variational transition state theory (MS-μVT) rate constants without tunneling. At low temperatures, the two approaches agree well with each other, but at high temperatures, SS-QRRK tends to overestimate falloff slightly. We also show that the variational effect is important in computing the energy-resolved rate constants. Multiple-structure anharmonicity, torsional-potential anharmonicity, and high-frequency-mode vibrational anharmonicity are all included in the rate computations, and torsional anharmonicity effects on the density of states are investigated. Branching fractions, which are both temperature- and pressure-dependent (and for which only limited data is available from experiment), are predicted as a function of pressure.
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Affiliation(s)
- Junwei Lucas Bao
- Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota , Minneapolis, Minnesota 55455-0431, United States
| | - Jingjing Zheng
- Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota , Minneapolis, Minnesota 55455-0431, United States
| | - Donald G Truhlar
- Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota , Minneapolis, Minnesota 55455-0431, United States
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16
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Zhu P, Duan XM, Liu JY. Theoretical studies on mechanism and kinetics of the hydrogen-abstraction reaction of CF3C(O)OCH2CH3 with OH radicals. J Fluor Chem 2015. [DOI: 10.1016/j.jfluchem.2015.05.014] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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17
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Bao JL, Meana-Pañeda R, Truhlar DG. Multi-path variational transition state theory for chiral molecules: the site-dependent kinetics for abstraction of hydrogen from 2-butanol by hydroperoxyl radical, analysis of hydrogen bonding in the transition state, and dramatic temperature dependence of the activation energy. Chem Sci 2015; 6:5866-5881. [PMID: 29861912 PMCID: PMC5950756 DOI: 10.1039/c5sc01848j] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2015] [Accepted: 06/15/2015] [Indexed: 01/20/2023] Open
Abstract
The goal of the present work is modeling the kinetics of a key reaction involved in the combustion of the biofuel 2-butanol. To accomplish this we extended multi-path variational transition state theory (MP-VTST) with the small curvature tunneling (SCT) approximation to include multistructural anharmonicity factors for molecules with chiral carbons. We use the resulting theory to predict the site-dependent rate constants of the hydrogen abstraction from 2-butanol by hydroperoxyl radical. The generalized transmission coefficients were averaged over the four lowest-energy reaction paths. The computed forward reaction rate constants indicate that hydrogen abstraction from the C-2 site has the largest contribution to the overall reaction from 200 K to 2400 K, with a contribution ranging from 99.9988% at 200 K to 88.9% at 800 K to 21.2% at 3000 K, while hydrogen abstraction from the oxygen site makes the lowest contribution at all temperatures, ranging from 2.5 × 10-9% at 200 K to 0.65% at 800 K to 18% at 3000 K. This work highlights the importance of including the multiple-structure and torsional potential anharmonicity in the computation of the thermal rate constants. We also analyzed the role played by the hydrogen bond at the transition state, and we illustrated the risks of (a) considering only the lowest-energy conformations in the calculations of the rate constants or (b) ignoring the nonlinear temperature dependence of the activation energies. A hydrogen bond at the transition state can lower the enthalpy of activation, but raise the free energy of activation. We find an energy of activation that increases from 11 kcal mol-1 at 200 K to more than 36 kcal mol-1 at high temperature for this radical reaction with a biofuel molecule.
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Affiliation(s)
- Junwei Lucas Bao
- Department of Chemistry , Chemical Theory Center and Supercomputing Institute , University of Minnesota , Minneapolis , Minnesota 55455-043 , USA .
| | - Rubén Meana-Pañeda
- Department of Chemistry , Chemical Theory Center and Supercomputing Institute , University of Minnesota , Minneapolis , Minnesota 55455-043 , USA .
| | - Donald G Truhlar
- Department of Chemistry , Chemical Theory Center and Supercomputing Institute , University of Minnesota , Minneapolis , Minnesota 55455-043 , USA .
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18
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Gong S, Luo Q, Wei GM. Theoretical Study of Mechanism and Dynamics on Reaction of (CH3)2NH with CH3. J Phys Chem A 2015; 119:4746-54. [DOI: 10.1021/acs.jpca.5b02443] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Shida Gong
- MOE
Key Laboratory of Theoretical Chemistry of Environment, Center for
Computational Quantum Chemistry, South China Normal University, Guangzhou 510006, P. R. China
| | - Qiong Luo
- MOE
Key Laboratory of Theoretical Chemistry of Environment, Center for
Computational Quantum Chemistry, South China Normal University, Guangzhou 510006, P. R. China
| | - Gong Min Wei
- Department
of Physics, Capital Normal University, Beijing 100048, P. R. China
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19
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Zhang L, Zhang P. Towards high-level theoretical studies of large biodiesel molecules: an ONIOM [QCISD(T)/CBS:DFT] study of hydrogen abstraction reactions of CnH2n+1COOCmH2m+1 + H. Phys Chem Chem Phys 2015; 17:200-8. [DOI: 10.1039/c4cp03004d] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Recent interest in biodiesel combustion urges the need for the theoretical chemical kinetics of large alkyl ester molecules.
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Affiliation(s)
- Lidong Zhang
- Department of Mechanical Engineering
- The Hong Kong Polytechnic University
- Kowloon
- Hong Kong
| | - Peng Zhang
- Department of Mechanical Engineering
- The Hong Kong Polytechnic University
- Kowloon
- Hong Kong
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20
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Bao JL, Seal P, Truhlar DG. Nanodusty plasma chemistry: a mechanistic and variational transition state theory study of the initial steps of silyl anion–silane and silylene anion–silane polymerization reactions. Phys Chem Chem Phys 2015; 17:15928-35. [DOI: 10.1039/c5cp01979f] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The aim of the present work is to understand the detailed reaction mechanisms in the growth of nanodusty particles, which is critical in plasma chemistry, physics and engineering.
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Affiliation(s)
- Junwei Lucas Bao
- Department of Chemistry
- Chemical Theory Center
- and Supercomputing Institute
- University of Minnesota
- Minneapolis
| | - Prasenjit Seal
- Department of Chemistry
- Chemical Theory Center
- and Supercomputing Institute
- University of Minnesota
- Minneapolis
| | - Donald G. Truhlar
- Department of Chemistry
- Chemical Theory Center
- and Supercomputing Institute
- University of Minnesota
- Minneapolis
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21
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Zheng J, Meana-Pañeda R, Truhlar DG. Prediction of Experimentally Unavailable Product Branching Ratios for Biofuel Combustion: The Role of Anharmonicity in the Reaction of Isobutanol with OH. J Am Chem Soc 2014; 136:5150-60. [DOI: 10.1021/ja5011288] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- Jingjing Zheng
- Department of Chemistry,
Chemical Theory Center, and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, United States
| | - Rubén Meana-Pañeda
- Department of Chemistry,
Chemical Theory Center, and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, United States
| | - Donald G. Truhlar
- Department of Chemistry,
Chemical Theory Center, and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, United States
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22
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Seal P, Truhlar DG. Large entropic effects on the thermochemistry of silicon nanodusty plasma constituents. J Am Chem Soc 2014; 136:2786-99. [PMID: 24432718 DOI: 10.1021/ja410498d] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Determination of the thermodynamic properties of reactor constituents is the first step in designing control strategies for plasma-mediated deposition processes and is also a key fundamental issue in physical chemistry. In this work, a recently proposed multistructural statistical thermodynamic method is used to show the importance of multiple structures and torsional anharmonicity in determining the thermodynamic properties of silicon hydride clusters, which are important both in plasmas and in thermally driven systems. It includes five different categories of silicon hydride clusters and radicals, including silanes, silyl radicals, and silenes. We employed a statistical mechanical approach, namely the recently developed multistructural (MS) anharmonicity method, in combination with density functional theory to calculate the partition functions, which in turn are used to estimate thermodynamic quantities, namely Gibbs free energy, enthalpy, entropy, and heat capacity, for all of the systems considered. The calculations are performed using all of the conformational structures of each molecule or radical by employing the multistructural quasiharmonic approximation (MS-QH) and also by including torsional potential anharmonicity (MS-T). For those cases where group additivity (GA) results are available, the thermodynamic quantities obtained from our MS-T calculations differ considerably due to the fact that the GA method is based on single-structure data for isomers of each stoichiometry, and hence lack multistructural effects; whereas we find that multistructural effects are very important in silicon hydride systems. Our results also indicate that the entropic effect on the thermochemistry is huge and is dominated by multistructural effects. The entropic effect of multiple structures is also expected to be important for other kinds of chain molecules, and its effect on nucleation kinetics is expected to be large.
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Affiliation(s)
- Prasenjit Seal
- Department of Chemistry, Supercomputing Institute, and Chemical Theory Center, University of Minnesota , Minneapolis, Minnesota 55455-0431, United States
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23
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Dames EE. Master Equation Modeling of the Unimolecular Decompositions of α-Hydroxyethyl (CH3
CHOH) and Ethoxy (CH3
CH2
O) Radicals. INT J CHEM KINET 2014. [DOI: 10.1002/kin.20844] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Enoch E. Dames
- High-Temperature Gasdynamics Laboratory; Department of Mechanical Engineering; Stanford University Stanford CA 94305
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24
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Klippenstein SJ, Pande VS, Truhlar DG. Chemical Kinetics and Mechanisms of Complex Systems: A Perspective on Recent Theoretical Advances. J Am Chem Soc 2014; 136:528-46. [DOI: 10.1021/ja408723a] [Citation(s) in RCA: 187] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Stephen J. Klippenstein
- Chemical
Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Vijay S. Pande
- Department
of Chemistry and Structural Biology, Stanford University, Stanford, California 94305, United States
| | - Donald G. Truhlar
- Department
of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, United States
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25
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26
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Jalan A, Alecu IM, Meana-Pañeda R, Aguilera-Iparraguirre J, Yang KR, Merchant SS, Truhlar DG, Green WH. New pathways for formation of acids and carbonyl products in low-temperature oxidation: the Korcek decomposition of γ-ketohydroperoxides. J Am Chem Soc 2013; 135:11100-14. [PMID: 23862563 DOI: 10.1021/ja4034439] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We present new reaction pathways relevant to low-temperature oxidation in gaseous and condensed phases. The new pathways originate from γ-ketohydroperoxides (KHP), which are well-known products in low-temperature oxidation and are assumed to react only via homolytic O-O dissociation in existing kinetic models. Our ab initio calculations identify new exothermic reactions of KHP forming a cyclic peroxide isomer, which decomposes via novel concerted reactions into carbonyl and carboxylic acid products. Geometries and frequencies of all stationary points are obtained using the M06-2X/MG3S DFT model chemistry, and energies are refined using RCCSD(T)-F12a/cc-pVTZ-F12 single-point calculations. Thermal rate coefficients are computed using variational transition-state theory (VTST) calculations with multidimensional tunneling contributions based on small-curvature tunneling (SCT). These are combined with multistructural partition functions (Q(MS-T)) to obtain direct dynamics multipath (MP-VTST/SCT) gas-phase rate coefficients. For comparison with liquid-phase measurements, solvent effects are included using continuum dielectric solvation models. The predicted rate coefficients are found to be in excellent agreement with experiment when due consideration is made for acid-catalyzed isomerization. This work provides theoretical confirmation of the 30-year-old hypothesis of Korcek and co-workers that KHPs are precursors to carboxylic acid formation, resolving an open problem in the kinetics of liquid-phase autoxidation. The significance of the new pathways in atmospheric chemistry, low-temperature combustion, and oxidation of biological lipids are discussed.
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Affiliation(s)
- Amrit Jalan
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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27
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McGillen MR, Baasandorj M, Burkholder JB. Gas-phase rate coefficients for the OH + n-, i-, s-, and t-butanol reactions measured between 220 and 380 K: non-Arrhenius behavior and site-specific reactivity. J Phys Chem A 2013; 117:4636-56. [PMID: 23627621 DOI: 10.1021/jp402702u] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Butanol (C4H9OH) is a potential biofuel alternative in fossil fuel gasoline and diesel formulations. The usage of butanol would necessarily lead to direct emissions into the atmosphere; thus, an understanding of its atmospheric processing and environmental impact is desired. Reaction with the OH radical is expected to be the predominant atmospheric removal process for the four aliphatic isomers of butanol. In this work, rate coefficients, k, for the gas-phase reaction of the n-, i-, s-, and t-butanol isomers with the OH radical were measured under pseudo-first-order conditions in OH using pulsed laser photolysis to produce OH radicals and laser induced fluorescence to monitor its temporal profile. Rate coefficients were measured over the temperature range 221-381 K at total pressures between 50 and 200 Torr (He). The reactions exhibited non-Arrhenius behavior over this temperature range and no dependence on total pressure with k(296 K) values of (9.68 ± 0.75), (9.72 ± 0.72), (8.88 ± 0.69), and (1.04 ± 0.08) (in units of 10(-12) cm(3) molecule(-1) s(-1)) for n-, i-, s-, and t-butanol, respectively. The quoted uncertainties are at the 2σ level and include estimated systematic errors. The observed non-Arrhenius behavior is interpreted here to result from a competition between the available H-atom abstraction reactive sites, which have different activation energies and pre-exponential factors. The present results are compared with results from previous kinetic studies, structure-activity relationships (SARs), and theoretical calculations and the discrepancies are discussed. Results from this work were combined with available high temperature (1200-1800 K) rate coefficient data and room temperature reaction end-product yields, where available, to derive a self-consistent site-specific set of reaction rate coefficients of the form AT(n) exp(-E/RT) for use in atmospheric and combustion chemistry modeling.
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Affiliation(s)
- Max R McGillen
- Chemical Sciences Division, Earth System Research Laboratory, National Oceanic and Atmospheric Administration, 325 Broadway, Boulder, Colorado 80305, USA
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28
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Zheng J, Truhlar DG. Quantum Thermochemistry: Multistructural Method with Torsional Anharmonicity Based on a Coupled Torsional Potential. J Chem Theory Comput 2013; 9:1356-67. [DOI: 10.1021/ct3010722] [Citation(s) in RCA: 118] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Jingjing Zheng
- Department of Chemistry, Chemical Theory Center, and
Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota
55455-0431, United States
| | - Donald G. Truhlar
- Department of Chemistry, Chemical Theory Center, and
Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota
55455-0431, United States
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29
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Seal P, Oyedepo G, Truhlar DG. Kinetics of the hydrogen atom abstraction reactions from 1-butanol by hydroxyl radical: theory matches experiment and more. J Phys Chem A 2013; 117:275-82. [PMID: 23244297 DOI: 10.1021/jp310910f] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
In the present work, we study the H atom abstraction reactions by hydroxyl radical at all five sites of 1-butanol. Multistructural variational transition state theory (MS-VTST) was employed to estimate the five thermal rate constants. MS-VTST utilizes a multifaceted dividing surface that accounts for the multiple conformational structures of the transition state, and we also include all the structures of the reactant molecule. The vibrational frequencies and minimum energy paths (MEPs) were computed using the M08-HX/MG3S electronic structure method. The required potential energy surfaces were obtained implicitly by direct dynamics employing interpolated variational transition state theory with mapping (IVTST-M) using a variational reaction path algorithm. The M08-HX/MG3S electronic model chemistry was then used to calculate multistructural torsional anharmonicity factors to complete the MS-VTST rate constant calculations. The results indicate that torsional anharmonicity is very important at higher temperatures, and neglecting it would lead to errors of 26 and 32 at 1000 and 1500 K, respectively. Our results for the sums of the site-specific rate constants agree very well with the experimental values of Hanson and co-workers at 896-1269 K and with the experimental results of Campbell et al. at 292 K, but slightly less well with the experiments of Wallington et al., Nelson et al., and Yujing and Mellouki at 253-372 K; nevertheless, the calculated rates are within a factor of 1.61 of all experimental values at all temperatures. This gives us confidence in the site-specific values, which are currently inaccessible to experiment.
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Affiliation(s)
- Prasenjit Seal
- Department of Chemistry and Supercomputing Institute, University of Minnesota, Minneapolis, MN 55455-0431, USA
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