Theoretical studies on the hydrogen abstraction reactions of methyl esters with HO<sub>2</sub>radical and the following β-scission reactions

Wang, Quan‐De

doi:10.1002/poc.3668

Cited by 11 publications

(11 citation statements)

References 42 publications

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“…One should note that the reaction of MA + HO 2 is endothermic at all four abstraction sites. Moreover, the relative energies of products are slightly higher than the corresponding TSs at S2 and S4 sites, similar to that in the H-abstraction reactions of methyl pentenoate + HO 2 performed by Wang at the CBS-QB3 level. Because of the bond between the O atom of the HO 2 radical and H atom of MA being fairly weak and the existence of strong CC double bonds, this reaction system is more endothermic than another three abstraction reaction systems.…”

Section: Results and Discussionsupporting

confidence: 75%

Multistructural Variational Reaction Kinetics of the Simplest Unsaturated Methyl Ester: H-Abstraction from Methyl Acrylate by H, OH, CH₃, and HO₂ Radicals

Ning

et al. 2021

J. Phys. Chem. A

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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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Section: Results and Discussionsupporting

confidence: 75%

Multistructural Variational Reaction Kinetics of the Simplest Unsaturated Methyl Ester: H-Abstraction from Methyl Acrylate by H, OH, CH₃, and HO₂ Radicals

Ning

et al. 2021

J. Phys. Chem. A

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“…Sun et al conducted a theoretical study of OH with butene isomers using transition state theory . Direct experimental or theoretical studies of longer chain alkenes (C5 and higher) are scarce in the literature, though a series of theoretical studies have been performed on small alkenes and biofuels. − Recently, Khaled et al measured and fitted the overall rate coefficients for the reaction of C4–C6 straight chain alkenes with OH by using a shock tube experiment . Despite this research, it has been highlighted that further refinement of some important kinetic parameters is still necessary.…”

Section: Introductionmentioning

confidence: 99%

Reaction Kinetics of Hydrogen Atom Abstraction from C4–C6 Alkenes by the Hydrogen Atom and Methyl Radical

Wang

Liu

2018

J. Phys. Chem. A

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Alkenes are important ingredients of realistic fuels and are also critical intermediates during the combustion of a series of other fuels including alkanes, cycloalkanes, and biofuels. To provide insights into the combustion behavior of alkenes, detailed quantum chemical studies for crucial reactions are desired. Hydrogen abstractions of alkenes play a very important role in determining the reactivity of fuel molecules. This work is motivated by previous experimental and modeling evidence that current literature rate coefficients for the abstraction reactions of alkenes are still in need of refinement and/or redetermination. In light of this, this work reports a theoretical and kinetic study of hydrogen atom abstraction reactions from C4-C6 alkenes by the hydrogen (H) atom and methyl (CH) radical. A series of C4-C6 alkene molecules with enough structural diversity are taken into consideration. Geometry and vibrational properties are determined at the B3LYP/6-31G(2df,p) level implemented in the Gaussian-4 (G4) composite method. The G4 level of theory is used to calculate the electronic single point energies for all species to determine the energy barriers. Conventional transition state theory with Eckart tunneling corrections is used to determine the high-pressure-limit rate constants for 47 elementary reaction rate coefficients. To faciliate their applications in kinetic modeling, the obtained rate constants are given in the Arrhenius expression and rate coefficients for typical reaction classes are recommended. The overall rate coefficients for the reaction of H atom and CH radical with all the studied alkenes are also compared. Branching ratios of these reaction channels for certain alkenes have also been analyzed.

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“…The test set includes a range of small to large surrogates of biodiesel esters, for example, 1,4-pentadiene, 3-hexene, methyl butanoate, methyl decanoate, and trans-4-methyl decanoate. The reactions considered involve 21 dispersion corrections. The BDEs representing the parent reactions, R1−R21, as illustrated in Figure 3, are first calculated by employing the 6-311++G(3df,2p) basis set using different DFT methods.…”

Section: Resultsmentioning

confidence: 99%

Eliminating Systematic Errors in DFT via Connectivity-Based Hierarchy: Accurate Bond Dissociation Energies of Biodiesel Methyl Esters

2019

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We present a computational study focusing on the determination of accurate bond dissociation energies (BDEs) involved in the combustion of biodiesel methyl esters. We have adapted our previously developed efficient error-cancellation protocols, based on the systematic "connectivity-based hierarchy" (CBH), to derive accurate BDEs of biodiesel molecules at a modest computational cost. Using DFT energies on the full biodiesel molecule in conjunction with accurate G4 energies on the small fragments involved in the CBH reaction schemes, systematic errors in the DFT methods can be cancelled efficiently. Herein, we apply our G4corrected ΔCBH-2 and ΔCBH-3 schemes in conjunction with several popular DFT methods to determine accurate bond dissociation energies of different C−C, C−H, and C−O bonds in biodiesel surrogate molecules. We first evaluate the performance of different DFT methods using a test set of 21 reactions involving various bond dissociations in small to medium biodiesel surrogates (up to methyl decanoate, a C10-methyl ester) by calibration against accurate values calculated with multireference methods (MRACPF2), reported by Carter and co-workers. The CBH-2 corrections for all tested dispersion-corrected functionals yield mean absolute deviations (MADs) in a narrow range of 1.3−1.5 kcal/mol, the best performance being obtained for B97-D3 and ωB97X-D functionals (MAD = 1.3 kcal/mol). Further, significant improvement yielding a MAD of only 0.9 kcal/mol is obtained using the G4-corrected CBH-3 scheme. Finally, the protocol has been applied to derive accurate BDEs of eight different bonds in the larger biodiesel molecule, methyl linolenate, yielding a MAD of only 1.13 kcal/mol using the ΔCBH-3 error correction scheme. The results suggest that our protocol in conjunction with different DFT methods should be broadly applicable to yield accurate BDEs for a variety of large biodiesel molecules.

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Theoretical studies on the hydrogen abstraction reactions of methyl esters with HO₂radical and the following β-scission reactions

Cited by 11 publications

References 42 publications

Multistructural Variational Reaction Kinetics of the Simplest Unsaturated Methyl Ester: H-Abstraction from Methyl Acrylate by H, OH, CH₃, and HO₂ Radicals

Multistructural Variational Reaction Kinetics of the Simplest Unsaturated Methyl Ester: H-Abstraction from Methyl Acrylate by H, OH, CH₃, and HO₂ Radicals

Reaction Kinetics of Hydrogen Atom Abstraction from C4–C6 Alkenes by the Hydrogen Atom and Methyl Radical

Eliminating Systematic Errors in DFT via Connectivity-Based Hierarchy: Accurate Bond Dissociation Energies of Biodiesel Methyl Esters

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Theoretical studies on the hydrogen abstraction reactions of methyl esters with HO2radical and the following β-scission reactions

Cited by 11 publications

References 42 publications

Multistructural Variational Reaction Kinetics of the Simplest Unsaturated Methyl Ester: H-Abstraction from Methyl Acrylate by H, OH, CH3, and HO2 Radicals

Multistructural Variational Reaction Kinetics of the Simplest Unsaturated Methyl Ester: H-Abstraction from Methyl Acrylate by H, OH, CH3, and HO2 Radicals

Reaction Kinetics of Hydrogen Atom Abstraction from C4–C6 Alkenes by the Hydrogen Atom and Methyl Radical

Eliminating Systematic Errors in DFT via Connectivity-Based Hierarchy: Accurate Bond Dissociation Energies of Biodiesel Methyl Esters

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Theoretical studies on the hydrogen abstraction reactions of methyl esters with HO₂radical and the following β-scission reactions

Multistructural Variational Reaction Kinetics of the Simplest Unsaturated Methyl Ester: H-Abstraction from Methyl Acrylate by H, OH, CH₃, and HO₂ Radicals

Multistructural Variational Reaction Kinetics of the Simplest Unsaturated Methyl Ester: H-Abstraction from Methyl Acrylate by H, OH, CH₃, and HO₂ Radicals