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Viegas LP. A Multiconformational Transition State Theory Approach to OH Tropospheric Degradation of Fluorotelomer Aldehydes. Chemphyschem 2023; 24:e202300259. [PMID: 37326576 DOI: 10.1002/cphc.202300259] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2023] [Revised: 06/09/2023] [Accepted: 06/12/2023] [Indexed: 06/17/2023]
Abstract
Experimental work on the OH-initiated oxidation reactions of fluorotelomer aldehydes (FTALs) strongly suggests that the respective rate coefficients do not depend on the size of the Cx F2x+1 fluoroalkyl chain. FTALs hence represent a challenging test to our multiconformer transition state theory (MC-TST) protocol based on constrained transition state randomization (CTSR), since the calculated rate coefficients should not show significant variations with increasing values of x ${x}$ . In this work we apply the MC-TST/CTSR protocol to thex = 2 , 3 ${x={\rm 2,3}}$ cases and calculate both rate coefficients at 298.15 K with a value ofk = ( 2 . 4 ± 1 . 4 ) × 10 - 12 ${k=(2.4\pm 1.4)\times {10}^{-12}}$ cm3 molecule-1 s-1 , practically coincident with the recommended experimental value of kexp =( 2 . 8 ± 1 . 4 ) × 10 - 12 ${(2.8\pm 1.4)\times {10}^{-12}}$ cm3 molecule-1 s-1 . We also show that the use of tunneling corrections based on improved semiclassical TST is critical in obtaining Arrhenius-Kooij curves with a correct behavior at lower temperatures.
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Affiliation(s)
- Luís P Viegas
- Coimbra Chemistry Centre-Institute of Molecular Sciences (CQC-IMS), Department of Chemistry, University of Coimbra, 3004-535, Coimbra, Portugal
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2
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Viegas LP. Gas-phase OH-oxidation of 2-butanethiol: Multiconformer transition state theory rate constant with constrained transition state randomization. Chem Phys Lett 2022. [DOI: 10.1016/j.cplett.2022.139829] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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3
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Wang Y, Zhang G, Shi X, Tang L, Ning Z. New insights in the hydrolysis mechanism of carbon disulfide (CS2): a density functional study. Struct Chem 2022. [DOI: 10.1007/s11224-022-01963-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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4
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Li J, Wang L, Wang L. Computational Study on the Reaction of β-Hydroxyethylperoxy Radical with HO 2 and Effects of Water Vapor. J Phys Chem A 2022; 126:2234-2243. [PMID: 35362984 DOI: 10.1021/acs.jpca.1c09009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The reaction of β-hydroxyethylperoxy radical (β-HEP) and HO2 with and without water was studied using quantum chemistry and kinetic calculations. The main products are HOCH2CH2OOH and 3O2 for the reaction with and without water, while all other reaction channels can be neglected. The rate coefficients of the reaction follow negative temperature dependence. The pseudo-second-order rate coefficients are 2-4 orders of magnitude smaller for the reaction with saturated water vapor, indicating the negligible contribution of water in this reaction. This is probably also true for other peroxy radicals (except for HO2), indicating that a large part of previous results on the water enhancement of reaction rate coefficients might have overestimated the influence of water.
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Affiliation(s)
- Junjie Li
- School of Chemistry & Chemical Engineering, South China University of Technology, Guangzhou 510640, China
| | - Lingyu Wang
- School of Chemistry & Chemical Engineering, South China University of Technology, Guangzhou 510640, China
| | - Liming Wang
- School of Chemistry & Chemical Engineering, South China University of Technology, Guangzhou 510640, China.,Guangdong Provincial Key Laboratory of Atmospheric Environment and Pollution Control, South China University of Technology, Guangzhou 510006, China
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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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6
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Galvão BRL, Viegas LP, Salahub DR, Lourenço MP. Reliability of semiempirical and DFTB methods for the global optimization of the structures of nanoclusters. J Mol Model 2020; 26:303. [PMID: 33064203 DOI: 10.1007/s00894-020-04484-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2020] [Accepted: 07/21/2020] [Indexed: 11/26/2022]
Abstract
In this work, we explore the possibility of using computationally inexpensive electronic structure methods, such as semiempirical and DFTB calculations, for the search of the global minimum (GM) structure of chemical systems. The basic prerequisite that these inexpensive methods will need to fulfill is that their lowest energy structures can be used as starting point for a subsequent local optimization at a benchmark level that will yield its GM. If this is possible, one could bypass the global optimization at the expensive method, which is currently impossible except for very small molecules. Specifically, we test our methods with clusters of second row elements including systems of several bonding types, such as alkali, metal, and covalent clusters. The results reveal that the DFTB3 method yields reasonable results and is a potential candidate for this type of applications. Even though the DFTB2 approach using standard parameters is proven to yield poor results, we show that a re-parametrization of only its repulsive part is enough to achieve excellent results, even when applied to larger systems outside the training set.
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Affiliation(s)
- Breno R L Galvão
- Centro Federal de Educação Tecnológica de Minas Gerais, CEFET-MG, Av. Amazonas 5253, Belo Horizonte, Minas Gerais, 30421-169, Brazil.
| | - Luís P Viegas
- Coimbra Chemistry Center and Chemistry Department, University of Coimbra, 3004-535, Coimbra, Portugal
| | - Dennis R Salahub
- Department of Chemistry, CMS - Centre for Molecular Simulation, IQST - Institute for Quantum Science and Technology, University of Calgary, 2500 University Drive NW, Calgary, AB, T2N 1N4, Canada
| | - Maicon P Lourenço
- Departamento de Química e Física, Centro de Ciências Exatas, Naturais e da Saúde (CCENS), Universidade Federal do Espírito Santo, Alegre, Espírito Santo, 29500-000, Brazil
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7
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McCoy AB. Virtual Issue on New Tools and Methods in Physical Chemistry Research. J Phys Chem A 2020; 124:4323-4324. [PMID: 32493016 DOI: 10.1021/acs.jpca.0c04262] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Anne B McCoy
- Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
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8
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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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de Souza Machado G, Martins EM, Baptista L, Bauerfeldt GF. Prediction of Rate Coefficients for the H 2CO + OH → HCO + H 2O Reaction at Combustion, Atmospheric and Interstellar Medium Conditions. J Phys Chem A 2020; 124:2309-2317. [PMID: 32091904 DOI: 10.1021/acs.jpca.9b11690] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Despite the relevance of the H2CO + OH → HCO + H2O reaction for combustion, atmospheric, and interstellar medium conditions, a large discrepancy on energetic and kinetic data for this reaction is still observed in the previous literature. In this work, this hydrogen abstraction reaction has been investigated at the CCSD(T)/CBS level of theory, suggesting that both the prebarrier complex and saddle point are stabilized in relation to the reactants by 3.31 and 1.35 kcal mol-1, respectively. Moreover, from the Gibbs free energy profile of the reaction coordinate, it has been verified that the formation of the prebarrier complex is endergonic, for temperatures above 550 K. Hence, for temperatures lower than 550 K, the reaction is described by a mechanism consisting of three elementary steps, while for higher temperatures it can be assumed to be an elementary reaction. Finally, the prediction of rate coefficients suggests that unified statistical rate theory best applies to the low temperature regime, while canonical variational rate coefficients better fit experimental data at the high temperature regime.
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Affiliation(s)
- Gladson de Souza Machado
- Instituto de Quı́mica, Universidade Federal Rural do Rio de Janeiro, BR-465 km 7, Seropédica, RJ, 23890-000 Brazil
| | - Eduardo Monteiro Martins
- Departamento de Engenharia Sanitária e do Meio Ambiente, Faculdade de Engenharia, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, RJ, 20550-900 Brazil
| | - Leonardo Baptista
- Departamento de Quı́mica e Ambiental, Faculdade de Tecnologia, Universidade do Estado do Rio de Janeiro, Rodovia Presidente Dutra km 298, Resende, RJ, 27537-000 Brazil
| | - Glauco F Bauerfeldt
- Instituto de Quı́mica, Universidade Federal Rural do Rio de Janeiro, BR-465 km 7, Seropédica, RJ, 23890-000 Brazil
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Galvão BRL, Viegas LP. What Electronic Structure Method Can Be Used in the Global Optimization of Nanoclusters? J Phys Chem A 2019; 123:10454-10462. [DOI: 10.1021/acs.jpca.9b09309] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Breno R. L. Galvão
- Centro Federal de Educação Tecnológica de Minas Gerais, CEFET-MG, Av. Amazonas 5253, 30421-169 Belo Horizonte, Minas Gerais, Brazil
| | - Luís P. Viegas
- Aarhus Institute of Advanced Studies, Aarhus University, Aarhus DK-8000, Denmark
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11
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Xing L, Wang Z, Truhlar DG. Multistructural Anharmonicity Controls the Radical Generation Process in Biofuel Combustion. J Am Chem Soc 2019; 141:18531-18543. [PMID: 31637914 DOI: 10.1021/jacs.9b09194] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The OH radical plays an important role in combustion, and isopentanol (3-methylbutan-1-ol) is a promising sustainable fuel additive and second-generation biofuel. The abstractions of H atoms from fuel molecules are key initiation steps for chain branching in combustion chemistry. In comparison with the more frequently studied ethanol, isopentanol has a longer carbon chain that allows a greater number of products, and experimental work is unavailable for the branching fractions to the various products. However, the site-dependent kinetics of isopentanol with OH radicals are usually experimentally unavailable. Alcohol oxidation by OH is also important in the atmosphere, and in the present study we calculate the rate constants and branching fractions of the hydrogen abstraction reaction of isopentanol by OH radical in a broad temperature range of 298-2400 K, covering temperatures important for atmospheric chemistry and those important for combustion. The calculations are done by multipath variational transition state theory (MP-VTST). With a combination of electronic structure calculations, we determine previously missing thermochemical data. With MP-VTST, a multidimensional tunneling approximation, multiple-structure anharmonicity, and torsional potential anharmonicity, we carried out more realistic rate constant calculations than can be computed by conventional single-structure harmonic transition state theory or by the empirical relations that are currently used in atmospheric and combustion modeling. The roles of various factors in determining the rates are elucidated, and we show that recrossing, tunneling, and multiple structures are all essential for accurate work. We conclude that the multiple structure anharmonicity is the most important correction to conventional transition state theory for this reaction, although recrossing effects and tunneling are by no means insignificant and the tunneling depends significantly on the path. The thermodynamic and kinetics data determined in this work are indispensable for the gas-phase degradation of alcohols in the atmosphere and for the detailed understanding and prediction of ignition mechanisms of biofuels in combustion.
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Affiliation(s)
- Lili Xing
- Energy and Power Engineering Institute , Henan University of Science and Technology , Luoyang , Henan 471003 , China.,Department of Chemistry, Chemical Theory Center, and Minnesota Supercomputing Institute , University of Minnesota , Minnesota 55455-0431 , United States
| | - Zhandong Wang
- National Synchrotron Radiation Laboratory , University of Science and Technology of China , Hefei , Anhui 230029 , PR 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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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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13
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Viegas LP. Multiconformer transition state theory rate constants for the reaction between OH and ‐dimethoxyfluoropolyethers. INT J CHEM KINET 2019. [DOI: 10.1002/kin.21259] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Luís P. Viegas
- Aarhus Institute of Advanced StudiesAarhus UniversityAarhus Denmark
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