1
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Gao Q, Shen C, Zhang H, Long B, Truhlar DG. Quantitative kinetics reveal that reactions of HO 2 are a significant sink for aldehydes in the atmosphere and may initiate the formation of highly oxygenated molecules via autoxidation. Phys Chem Chem Phys 2024; 26:16160-16174. [PMID: 38787752 DOI: 10.1039/d4cp00693c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/26/2024]
Abstract
Large aldehydes are widespread in the atmosphere and their oxidation leads to secondary organic aerosols. The current understanding of their chemical transformation processes is limited to hydroxyl radical (OH) oxidation during daytime and nitrate radical (NO3) oxidation during nighttime. Here, we report quantitative kinetics calculations of the reactions of hexanal (C5H11CHO), pentanal (C4H9CHO), and butanal (C3H7CHO) with hydroperoxyl radical (HO2) at atmospheric temperatures and pressures. We find that neither tunneling nor multistructural torsion anharmonicity should be neglected in computing these rate constants; strong anharmonicity at the transition states is also important. We find rate constants for the three reactions in the range 3.2-7.7 × 10-14 cm3 molecule-1 s-1 at 298 K and 1 atm, showing that the HO2 reactions can be competitive with OH and NO3 oxidation under some conditions relevant to the atmosphere. Our findings reveal that HO2-initiated oxidation of large aldehydes may be responsible for the formation of highly oxygenated molecules via autoxidation. We augment the theoretic studies with laboratory flow-tube experiments using an iodide-adduct time-of-flight chemical ionization mass spectrometer to confirm the theoretical predictions of peroxy radicals and the autoxidation pathway. We find that the adduct from HO2 + C5H11CHO undergoes a fast unimolecular 1,7-hydrogen shift with a rate constant of 0.45 s-1. We suggest that the HO2 reactions make significant contributions to the sink of aldehydes.
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Affiliation(s)
- Qiao Gao
- School of Physics and Mechatronic Engineering, Guizhou Minzu University, Guiyang 550025, China.
| | - Chuanyang Shen
- Department of Chemistry, University of California, Riverside, California, 92507, USA.
| | - Haofei Zhang
- Department of Chemistry, University of California, Riverside, California, 92507, USA.
| | - Bo Long
- School of Physics and Mechatronic Engineering, Guizhou Minzu University, Guiyang 550025, China.
- College of Materials Science and Engineering, Guizhou Minzu university, Guiyang 550025, China
| | - Donald G Truhlar
- Department of Chemistry, Chemical Theory Center, and Minnesota Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, USA.
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2
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He Y, Xing L, Zhu Q, Lian L, Wang X, Liu M, Cheng Z. Theoretical Kinetic Study on Hydrogen Abstraction Reactions from n-Pentane by NO 2. J Phys Chem A 2023; 127:10243-10252. [PMID: 37983021 DOI: 10.1021/acs.jpca.3c05054] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2023]
Abstract
The interaction of fuel with NOx chemistry is important for the construction of the reaction mechanism and engine application. In this work, the reaction pathways of nC5H12 + NO2 were studied by high-level electronic structure calculations (DLPNO-CCSD(T)-F12/cc-pVTZ-F12//B2PLYPD3/cc-pVTZ). The rate constants were calculated by using the multistructural canonical transition-state theory with the Eckart tunneling method (TST/MS-T/ET). The studied condition is in a wide temperature range of 298-2400 K. The influence of MS-T anharmonicity and tunneling effect will be clarified for these site-specific H-abstraction pathways. The result reflects the large deviation introduced by the treatment of MS-T anharmonicity, especially at a high temperature. For the same type of reactions, the rate constants of H-abstraction both occurring at the secondary carbon are not almost identical. The branching ratios show that abstraction from the secondary site forming cis-HONO (R2c) contributes 36-78% to nC5H12 consumption in the temperature range of 298-2400 K. The current results show that the multistructural torsional anharmonicity has a crucial influence on the accurate estimation of branching ratios.
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Affiliation(s)
- Yunrui He
- Energy and Power Engineering Institute, Henan University of Science and Technology, Luoyang, Henan 471003, PR China
| | - Lili Xing
- Energy and Power Engineering Institute, Henan University of Science and Technology, Luoyang, Henan 471003, PR China
| | - Qiongxuan Zhu
- Energy and Power Engineering Institute, Henan University of Science and Technology, Luoyang, Henan 471003, PR China
| | - Liuchao Lian
- Energy and Power Engineering Institute, Henan University of Science and Technology, Luoyang, Henan 471003, PR China
| | - Xuetao Wang
- Energy and Power Engineering Institute, Henan University of Science and Technology, Luoyang, Henan 471003, PR China
| | - Mengjie Liu
- Energy and Power Engineering Institute, Henan University of Science and Technology, Luoyang, Henan 471003, PR China
| | - Zhanjun Cheng
- School of Environmental Science and Engineering, Tianjin University, Tianjin 300072, P. R. China
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3
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Sun Y, Long B, Truhlar DG. Unimolecular Reactions of E-Glycolaldehyde Oxide and Its Reactions with One and Two Water Molecules. RESEARCH (WASHINGTON, D.C.) 2023; 6:0143. [PMID: 37435010 PMCID: PMC10332847 DOI: 10.34133/research.0143] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Accepted: 04/20/2023] [Indexed: 07/13/2023]
Abstract
The kinetics of Criegee intermediates are important for atmospheric modeling. However, the quantitative kinetics of Criegee intermediates are still very limited, especially for those with hydroxy groups. Here, we calculate rate constants for the unimolecular reaction of E-glycolaldehyde oxide [E-hydroxyethanal oxide, E-(CH2OH)CHOO], for its reactions with H2O and (H2O)2, and for the reaction of the E-(CH2OH)CHOO…H2O complex with H2O. For the highest level of electronic structure, we use W3X-L//CCSD(T)-F12a/cc-pVDZ-F12 for the unimolecular reaction and the reaction with water and W3X-L//DF-CCSD(T)-F12b/jun-cc-pVDZ for the reaction with 2 water molecules. For the dynamics, we use a dual-level strategy that combines conventional transition state theory with the highest level of electronic structure and multistructural canonical variational transition state theory with small-curvature tunneling with a validated density functional for the electronic structure. This dynamical treatment includes high-frequency anharmonicity, torsional anharmonicity, recrossing effects, and tunneling. We find that the unimolecular reaction of E-(CH2OH)CHOO depends on both temperature and pressure. The calculated results show that E-(CH2OH)CHOO…H2O + H2O is the dominant entrance channel, while previous investigations only considered Criegee intermediates + (H2O)2. In addition, we find that the atmospheric lifetime of E-(CH2OH)CHOO with respect to 2 water molecules is particularly short with a value of 1.71 × 10-6 s at 0 km, which is about 2 orders of magnitude shorter than those usually assumed for Criegee intermediate reactions with water dimer. We also find that the OH group in E-(CH2OH)CHOO enhances its reactivity.
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Affiliation(s)
- Yan Sun
- Department of Physics, Guizhou University, Guiyang 550025, China
| | - Bo Long
- Department of Physics, Guizhou University, Guiyang 550025, China
- College of Materials Science and Engineering, Guizhou Minzu University, Guiyang 550025, China
| | - Donald G. Truhlar
- Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota, Minneapolis, MN 55455-0431, USA
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4
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Xing L, Lian L, Wang Z, Cheng Z, He Y, Cui J, Truhlar DG. Lowering of Reaction Rates by Energetically Favorable Hydrogen Bonding in the Transition State. Degradation of Biofuel Ketohydroperoxides by OH. J Am Chem Soc 2022; 144:16984-16995. [PMID: 36069709 DOI: 10.1021/jacs.2c06124] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Ketohydroperoxides (KHPs) are oxygenates with carbonyl and hydroperoxy functional groups, and they are generated under combustion and atmospheric conditions. Their fate is crucial for secondary organic aerosol formation in the troposphere and for the ignition processes of biofuels in advanced combustion engines. We investigated the thermodynamics and kinetics of nine hydrogen abstraction reactions from four ether KHPs by OH. We find that the rate constants are strongly affected by entropic effects whose estimation requires a consideration of higher-energy conformers of the transition state. A density functional was selected for these reactions by comparison to coupled cluster calculations, and it was used for calculations by multistructural canonical transition-state theory with multidimensional tunneling over the temperature range of 200-2000 K. We find that the effect of multistructural torsional anharmonicity is very large and quite different for the various ether KHP reactions. A leading cause of the structural dependence is the dominance of entropic factors due to the lack of hydrogen bonding in some of the higher-energy conformers of the transition states. Four of the reactions involve abstraction from the α-carbon (the carbon vicinal to the hydroperoxide group); they exhibit nonmonotonic temperature dependence with complex fuel-specific dependence. The rate constants for abstraction from a non-α-carbon of a given KHP can be faster than the ones for abstraction from an α-carbon; in two cases, this is due to entropy, and in one case, the non-α-carbon abstraction has a lower energy barrier. Tunneling and recrossing effects are also found to be important.
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Affiliation(s)
- Lili Xing
- Energy and Power Engineering Institute, Henan University of Science and Technology, Luoyang 471003, Henan, China.,Department of Chemistry, Chemical Theory Center, and Minnesota Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, United States
| | - Liuchao Lian
- Energy and Power Engineering Institute, Henan University of Science and Technology, Luoyang 471003, Henan, China
| | - Zhandong Wang
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029, Anhui, China
| | - Zhanjun Cheng
- School of Environmental Science and Engineering, Tianjin University, Tianjin 300072, China
| | - Yunrui He
- Energy and Power Engineering Institute, Henan University of Science and Technology, Luoyang 471003, Henan, China
| | - Jintao Cui
- Energy and Power Engineering Institute, Henan University of Science and Technology, Luoyang 471003, Henan, China
| | - Donald G Truhlar
- Department of Chemistry, Chemical Theory Center, and Minnesota Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, United States
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5
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Kossaka Macedo G, Haiduke RLA. The performance of exchange-correlation functionals in describing electron density parameters of saddle point structures along chemical reactions. J Comput Chem 2022; 43:1830-1838. [PMID: 36053978 DOI: 10.1002/jcc.26985] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Revised: 05/26/2022] [Accepted: 08/03/2022] [Indexed: 11/07/2022]
Abstract
This work is focused on evaluating the performance of exchange-correlation functionals from density functional theory in providing descriptor values derived from the electron density of saddle point structures (transition states) in chemical reactions. The properties investigated were obtained from the quantum theory of atoms in molecules, including atomic charges and electron density topological data at the bond critical points. In addition, parameters from the Interacting quantum atom energy partition were used as well in this comparative study. The reference values are attained in coupled cluster calculations with iterative single and double excitations (CCSD). Six elementary reactions are considered here: CO + H2 ↔ H2 CO, CO + H2 O ↔ HCOOH, HCN ↔ HNC, H + F2 ↔ HF + F, H + N2 ↔ HN2 , and H + CO ↔ HCO. In general, the BB1K functional (hybrid-meta-generalized gradient approximation) provides the best description of these properties. Our study indicates that an intermediate percentage of nonlocal exact exchange, around 40%-55% (perhaps even larger), is probably required for attaining more accurate values with actual functionals, although this condition is not able of explaining all the trends observed.
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Affiliation(s)
- Gabriel Kossaka Macedo
- Department of Chemistry and Molecular Physics, São Carlos Institute of Chemistry, University of São Paulo, São Paulo, Brazil
| | - Roberto Luiz Andrade Haiduke
- Department of Chemistry and Molecular Physics, São Carlos Institute of Chemistry, University of São Paulo, São Paulo, Brazil
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6
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Xia Y, Long B, Lin S, Teng C, Bao JL, Truhlar DG. Large Pressure Effects Caused by Internal Rotation in the s-cis-syn-Acrolein Stabilized Criegee Intermediate at Tropospheric Temperature and Pressure. J Am Chem Soc 2022; 144:4828-4838. [PMID: 35262353 DOI: 10.1021/jacs.1c12324] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Criegee intermediates are important atmospheric oxidants, and quantitative kinetics for stabilized Criegee intermediates are key parameters for atmospheric modeling but are still limited. Here we report barriers and rate constants for unimolecular reactions of s-cis-syn-acrolein oxide (scsAO), in which the vinyl group makes it a prototype for Criegee intermediates produced in the ozonolysis of isoprene. We find that the MN15-L and M06-2X density functionals have CCSD(T)/CBS accuracy for the unimolecular cyclization and stereoisomerization of scsAO. We calculated high-pressure-limit rate constants by the dual-level strategy that combines (a) high-level wave function-based conventional transition-state theory (which includes coupled-cluster calculations with quasiperturbative inclusion of quadruple excitations because of the strongly multiconfigurational character of the electronic wave function) and (b) canonical variational transition-state theory with small-curvature tunneling based on a validated density functional. We calculated pressure-dependent rate constants both by system-specific quantum Rice-Ramsperger-Kassel theory and by solving the master equation. We report rate constants for unimolecular reactions of scsAO over the full range of atmospheric temperature and pressure. We found that the unimolecular reaction rates of this larger-than-previously studied Criegee intermediate depend significantly on pressure. Particularly, we found that falloff effects decrease the effective unimolecular cyclization rate constant of scsAO by about a factor of 3, but the unimolecular reaction is still the dominant atmospheric sink for scsAO at low altitudes. The large falloff caused by the inclusion of the stereoisomerization channel in the master equation calculations has broad implications for mechanistic analysis of reactions with competitive internal rotations that can produce stable rotamers.
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Affiliation(s)
- Yu Xia
- College of Mechanical and Electrical Engineering, Guizhou Minzu University, Guiyang 550025, China.,College of Materials Science and Engineering, Guizhou Minzu University, Guiyang 550025, China
| | - Bo Long
- College of Mechanical and Electrical Engineering, Guizhou Minzu University, Guiyang 550025, China.,College of Materials Science and Engineering, Guizhou Minzu University, Guiyang 550025, China
| | - Shiru Lin
- Department of Chemistry, Boston College, Chestnut Hill, Massachusetts 02467, United States
| | - Chong Teng
- Department of Chemistry, Boston College, Chestnut Hill, Massachusetts 02467, United States
| | - Junwei Lucas Bao
- Department of Chemistry, Boston College, Chestnut Hill, Massachusetts 02467, 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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7
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Hasan G, Salo VT, Valiev RR, Kubečka J, Kurtén T. Comparing Reaction Routes for 3(RO···OR') Intermediates Formed in Peroxy Radical Self- and Cross-Reactions. J Phys Chem A 2020; 124:8305-8320. [PMID: 32902986 DOI: 10.1021/acs.jpca.0c05960] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Organic peroxy radicals (RO2) are key intermediates in the chemistry of the atmosphere. One of the main sink reactions of RO2 is the recombination reaction RO2 + R'O2, which has three main channels (all with O2 as a coproduct): (1) R-H═O + R'OH, (2) RO + R'O, and (3) ROOR'. The RO + R'O "alkoxy" channel promotes radical and oxidant recycling, while the ROOR' "dimer" channel leads to low-volatility products relevant to aerosol processes. The ROOR' channel has only recently been discovered to play a role in the gas phase. Recent computational studies indicate that all of these channels first go through an intermediate complex 1(RO···3O2···OR'). Here, 3O2 is very weakly bound and will likely evaporate from the system, giving a triplet cluster of two alkoxy radicals: 3(RO···OR'). In this study, we systematically investigate the three reaction channels for an atmospherically representative set of RO + R'O radicals formed in the corresponding RO2 + R'O2 reaction. First, we systematically sample the possible conformations of the RO···OR' clusters on the triplet potential energy surface. Next, we compute energetic parameters and attempt to estimate reaction rate coefficients for the three channels: evaporation/dissociation to RO + R'O, a hydrogen shift leading to the formation of R'-H═O + ROH, and "spin-flip" (intersystem crossing) leading to, or at least allowing, the formation of ROOR' dimers. While large uncertainties in the computed energetics prevent a quantitative comparison of reaction rates, all three channels were found to be very fast (with typical rates greater than 106 s-1). This qualitatively demonstrates that the computationally proposed novel RO2 + R'O2 reaction mechanism is compatible with experimental data showing non-negligible branching ratios for all three channels, at least for sufficiently complex RO2.
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Affiliation(s)
- Galib Hasan
- Department of Chemistry, University of Helsinki, P.O. Box 55, FIN-00014 Helsinki, Finland.,Institute for Atmospheric and Earth System Research, Faculty of Science, University of Helsinki, FIN-00014 Helsinki, Finland
| | - Vili-Taneli Salo
- Department of Chemistry, University of Helsinki, P.O. Box 55, FIN-00014 Helsinki, Finland.,Institute for Atmospheric and Earth System Research, Faculty of Science, University of Helsinki, FIN-00014 Helsinki, Finland
| | - Rashid R Valiev
- Department of Chemistry, University of Helsinki, P.O. Box 55, FIN-00014 Helsinki, Finland.,Institute for Atmospheric and Earth System Research, Faculty of Science, University of Helsinki, FIN-00014 Helsinki, Finland
| | - Jakub Kubečka
- Institute for Atmospheric and Earth System Research, Faculty of Science, University of Helsinki, FIN-00014 Helsinki, Finland
| | - Theo Kurtén
- Department of Chemistry, University of Helsinki, P.O. Box 55, FIN-00014 Helsinki, Finland.,Institute for Atmospheric and Earth System Research, Faculty of Science, University of Helsinki, FIN-00014 Helsinki, Finland
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8
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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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9
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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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10
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Long B, Bao JL, Truhlar DG. Unimolecular reaction of acetone oxide and its reaction with water in the atmosphere. Proc Natl Acad Sci U S A 2018; 115:6135-6140. [PMID: 29844185 PMCID: PMC6004451 DOI: 10.1073/pnas.1804453115] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Criegee intermediates (i.e., carbonyl oxides with two radical sites) are known to be important atmospheric reagents; however, our knowledge of their reaction kinetics is still limited. Although experimental methods have been developed to directly measure the reaction rate constants of stabilized Criegee intermediates, the experimental results cover limited temperature ranges and do not completely agree well with one another. Here we investigate the unimolecular reaction of acetone oxide [(CH3)2COO] and its bimolecular reaction with H2O to obtain rate constants with quantitative accuracy comparable to experimental accuracy. We do this by using CCSDT(Q)/CBS//CCSD(T)-F12a/DZ-F12 benchmark results to select and validate exchange-correlation functionals, which are then used for direct dynamics calculations by variational transition state theory with small-curvature tunneling and torsional and high-frequency anharmonicity. We find that tunneling is very significant in the unimolecular reaction of (CH3)2COO and its bimolecular reaction with H2O. We show that the atmospheric lifetimes of (CH3)2COO depend on temperature and that the unimolecular reaction of (CH3)2COO is the dominant decay mode above 240 K, while the (CH3)2COO + SO2 reaction can compete with the corresponding unimolecular reaction below 240 K when the SO2 concentration is 9 × 1010 molecules per cubic centimeter. We also find that experimental results may not be sufficiently accurate for the unimolecular reaction of (CH3)2COO above 310 K. Not only does the present investigation provide insights into the decay of (CH3)2COO in the atmosphere, but it also provides an illustration of how to use theoretical methods to predict quantitative rate constants of medium-sized Criegee intermediates.
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Affiliation(s)
- Bo Long
- College of Materials Science and Engineering, Guizhou Minzu University, 550025 Guiyang, China;
- Department of Chemistry, Chemical Theory Center, University of Minnesota, Minneapolis, MN 55455-0431
- Supercomputing Institute, University of Minnesota, Minneapolis, MN 55455-0431
| | - Junwei Lucas Bao
- Department of Chemistry, Chemical Theory Center, University of Minnesota, Minneapolis, MN 55455-0431
- Supercomputing Institute, University of Minnesota, Minneapolis, MN 55455-0431
| | - Donald G Truhlar
- Department of Chemistry, Chemical Theory Center, University of Minnesota, Minneapolis, MN 55455-0431;
- Supercomputing Institute, University of Minnesota, Minneapolis, MN 55455-0431
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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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Bao JL, Truhlar DG. Effect of energy dependence of the density of states on pressure-dependent rate constants. Phys Chem Chem Phys 2018; 20:30475-30479. [DOI: 10.1039/c8cp05915b] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The rate of collisional energy transfer is slowed down by the increase in the density of states at higher energies.
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Affiliation(s)
- Junwei Lucas Bao
- Department of Chemistry
- Chemical Theory Center, and Supercomputing Institute
- University of Minnesota
- Minneapolis
- USA
| | - Donald G. Truhlar
- Department of Chemistry
- Chemical Theory Center, and Supercomputing Institute
- University of Minnesota
- Minneapolis
- USA
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13
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Xing L, Bao JL, Wang Z, Zhang F, Truhlar DG. Degradation of Carbonyl Hydroperoxides in the Atmosphere and in Combustion. J Am Chem Soc 2017; 139:15821-15835. [PMID: 29022349 DOI: 10.1021/jacs.7b08297] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Oxygenates with carbonyl and hydroperoxy functional groups are important intermediates that are generated during the autoxidation of organic compounds in the atmosphere and during the autoignition of transport fuels. In the troposphere, the degradation of carbonyl hydroperoxides leads to low-vapor-pressure polyfunctional species that may precipitate in clouds and fog droplets or to the formation of secondary organic aerosols (SOAs). In combustion, the fate of carbonyl hydroperoxides is important for the performance of advanced combustion engines, especially for autoignition. A key fate of the carbonyl hydroperoxides is reaction with OH radicals, for which kinetics data are experimentally unavailable. Here, we study 4-hydroperoxy-2-pentanone (CH3C(═O)CH2CH(OOH)CH3) as a model compound to clarify the kinetics of OH reactions with carbonyl hydroperoxides, in particular H atom abstraction and OH addition reactions. With a combination of electronic structure calculations, we determine previously missing thermochemical data, and with multipath variational transition state theory (MP-VTST), a multidimensional tunneling (MT) approximation, multiple-structure anharmonicity, and torsional potential anharmonicity, we obtained much more accurate rate constants than the ones that can computed by conventional single-structure harmonic transition state theory (TST) and than the empirically estimated rate constants that are currently used in atmospheric and combustion modeling. The roles of various factors in determining the rates are elucidated. The pressure-dependent rate constants for the addition reaction are computed using system-specific quantum RRK theory. The calculated temperature range is 298-2400 K, and the pressure range is 0.01-100 atm. The accurate thermodynamic and kinetics data determined in this work are indispensable in the global modeling of SOAs in atmospheric science and in the detailed understanding and prediction of ignition properties of hydrocarbons and alternative fuels.
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Affiliation(s)
- Lili Xing
- National Synchrotron Radiation Laboratory, University of Science and Technology of China , Hefei, Anhui 230029, China.,Department of Chemistry, Chemical Theory Center, and Minnesota Supercomputing Institute, University of Minnesota , Minnesota 55455-0431, United States
| | - Junwei Lucas Bao
- Department of Chemistry, Chemical Theory Center, and Minnesota Supercomputing Institute, University of Minnesota , Minnesota 55455-0431, United States
| | - Zhandong Wang
- King Abdullah University of Science and Technology (KAUST) , Clean Combustion Research Center (CCRC), Thuwal, 23955-6900, Saudi Arabia
| | - Feng Zhang
- National Synchrotron Radiation Laboratory, University of Science and Technology of China , Hefei, Anhui 230029, 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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Bao JL, Xing L, Truhlar DG. Dual-Level Method for Estimating Multistructural Partition Functions with Torsional Anharmonicity. J Chem Theory Comput 2017; 13:2511-2522. [DOI: 10.1021/acs.jctc.7b00232] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Junwei Lucas Bao
- Department of Chemistry, Chemical Theory
Center, and Minnesota Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, United States
| | - Lili Xing
- Department of Chemistry, Chemical Theory
Center, and Minnesota Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, United States
| | - Donald G. Truhlar
- Department of Chemistry, Chemical Theory
Center, and Minnesota Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, United States
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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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16
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Abstract
We theoretically investigate the rate constantk(T,p) of the OH + SO2reaction with experimental accuracy.
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Affiliation(s)
- Bo Long
- College of Material Science and Engineering
- Guizhou Minzu University
- Guiyang
- China
- Department of Chemistry
| | - Junwei Lucas Bao
- Department of Chemistry
- Chemical Theory Center, and Supercomputing Institute
- University of Minnesota
- Minneapolis
- USA
| | - Donald G. Truhlar
- Department of Chemistry
- Chemical Theory Center, and Supercomputing Institute
- University of Minnesota
- Minneapolis
- USA
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17
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Long B, Tan XF, Bao JL, Wang DM, Long ZW. Theoretical Study of the Reaction Mechanism and Kinetics of HO2with XCHO (X = F, Cl). INT J CHEM KINET 2016. [DOI: 10.1002/kin.21062] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- Bo Long
- College of Computer and Information Engineering; Guizhou MinZu University; Guiyang 550025 People's Republic of China
| | - Xing-Feng Tan
- College of Computer and Information Engineering; Guizhou MinZu University; Guiyang 550025 People's Republic of China
| | - Junwei Lucas Bao
- Department of Chemistry; Chemical Theory Center, and Supercomputing Institute; University of Minnesota; Minneapolis MN 55455
| | - Ding-Mei Wang
- Department of Physics; Guizhou University; Guiyang 550025 People's Republic of China
| | - Zheng-Wen Long
- Department of Physics; Guizhou University; Guiyang 550025 People's Republic of China
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18
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Mon-Pérez E, Salazar J, Ramos E, Salazar JS, Suárez AL, Dutt A, Santana G, Monroy BM. Experimental and theoretical rationalization of the growth mechanism of silicon quantum dots in non-stoichiometric SiN x : role of chlorine in plasma enhanced chemical vapour deposition. NANOTECHNOLOGY 2016; 27:455703. [PMID: 27698286 DOI: 10.1088/0957-4484/27/45/455703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Silicon quantum dots (Si-QDs) embedded in an insulator matrix are important from a technological and application point of view. Thus, being able to synthesize them in situ during the matrix growth process is technologically advantageous. The use of SiH2Cl2 as the silicon precursor in the plasma enhanced chemical vapour deposition (PECVD) process allows us to obtain Si-QDs without post-thermal annealing. Foremost in this work, is a theoretical rationalization of the mechanism responsible for Si-QD generation in a film including an analysis of the energy released by the extraction of HCl and the insertion of silylene species into the terminal surface bonds. From the results obtained using density functional theory (DFT), we propose an explanation of the mechanism responsible for the formation of Si-QDs in non-stoichiometric SiN x starting from chlorinated precursors in a PECVD system. Micrograph images obtained through transmission electron microscopy confirmed the presence of Si-QDs, even in nitrogen-rich (N-rich) samples. The film stoichiometry was controlled by varying the growth parameters, in particular the NH3/SiH2Cl2 ratio and hydrogen dilution. Experimental and theoretical results together show that using a PECVD system, along with chlorinated precursors it is possible to obtain Si-QDs at a low substrate temperature without annealing treatment. The optical property studies carried out in the present work highlight the prospects of these thin films for down shifting and as an antireflection coating in silicon solar cells.
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Affiliation(s)
- E Mon-Pérez
- Departamento de Materiales de Baja Dimensionalidad, Instituto de Investigaciones en Materiales, UNAM, Circuito Exterior s/n, C. U., A. P. 70-360, Coyoacán, C. P. 04510, México, D. F., Mexico
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Barrierless association of CF2 and dissociation of C2F4 by variational transition-state theory and system-specific quantum Rice-Ramsperger-Kassel theory. Proc Natl Acad Sci U S A 2016; 113:13606-13611. [PMID: 27834727 DOI: 10.1073/pnas.1616208113] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Bond dissociation is a fundamental chemical reaction, and the first principles modeling of the kinetics of dissociation reactions with a monotonically increasing potential energy along the dissociation coordinate presents a challenge not only for modern electronic structure methods but also for kinetics theory. In this work, we use multifaceted variable-reaction-coordinate variational transition-state theory (VRC-VTST) to compute the high-pressure limit dissociation rate constant of tetrafluoroethylene (C2F4), in which the potential energies are computed by direct dynamics with the M08-HX exchange correlation functional. To treat the pressure dependence of the unimolecular rate constants, we use the recently developed system-specific quantum Rice-Ramsperger-Kassel theory. The calculations are carried out by direct dynamics using an exchange correlation functional validated against calculations that go beyond coupled-cluster theory with single, double, and triple excitations. Our computed dissociation rate constants agree well with the recent experimental measurements.
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Long B, Bao JL, Truhlar DG. Atmospheric Chemistry of Criegee Intermediates: Unimolecular Reactions and Reactions with Water. J Am Chem Soc 2016; 138:14409-14422. [PMID: 27682870 DOI: 10.1021/jacs.6b08655] [Citation(s) in RCA: 200] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Criegee intermediates are produced in the ozonolysis of unsaturated hydrocarbons in the troposphere, and understanding their fate is a prerequisite to modeling climate-controlling atmospheric aerosol formation. Although some experimental and theoretical rate data are available, they are incomplete and partially inconsistent, and they do not cover the tropospheric temperature range. Here, we report quantum chemical rate constants for the reactions of stabilized formaldehyde oxide (CH2OO) and acetaldehyde oxide (syn-CH3CHOO and anti-CH3CHOO) with H2O and for their unimolecular reactions. Our results are obtained by combining post-CCSD(T) electronic structure benchmarks, validated density functional theory potential energy surfaces, and multipath variational transition state theory with multidimensional tunneling, coupled-torsions anharmonicity, and high-frequency anharmonicity. We consider two different types of reaction mechanisms for the bimolecular reactions, namely, (i) addition-coupled hydrogen transfer and (ii) double hydrogen atom transfer (DHAT). First, we show that the MN15-L exchange-correlation functional has kJ/mol accuracy for the CH2OO + H2O and syn-CH3CHOO + H2O reactions. Then we show that, due to tunneling, the DHAT mechanism is especially important in the syn-CH3CHOO + H2O reaction. We show that the dominant pathways for reactions of Criegee intermediates depend on altitude. The results we obtain eliminate the discrepancy between experiment and theory under those conditions where experimental results are available, and we make predictions for the full range of temperatures and pressures encountered in the troposphere and stratosphere. The present results are an important cog in clarifying the atmospheric fate and oxidation processes of Criegee intermediates, and they also show how theoretical methods can provide reliable rate data for complex atmospheric processes.
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Affiliation(s)
- Bo Long
- College of Information Engineering, Guizhou Minzu University , Guiyang 550025, China.,Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota , Minneapolis, Minnesota 55455-0431, United States
| | - Junwei Lucas Bao
- 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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