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Thawoos S, Suas-David N, Gurusinghe RM, Edlin M, Behzadfar A, Lang J, Suits AG. Low temperature reaction kinetics inside an extended Laval nozzle: REMPI characterization and detection by broadband rotational spectroscopy. J Chem Phys 2023; 159:214201. [PMID: 38054511 DOI: 10.1063/5.0178533] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Accepted: 11/06/2023] [Indexed: 12/07/2023] Open
Abstract
Chirped-Pulse Fourier-Transform millimeter wave (CP-FTmmW) spectroscopy is a powerful method that enables detection of quantum state specific reactants and products in mixtures. We have successfully coupled this technique with a pulsed uniform Laval flow system to study photodissociation and reactions at low temperature, which we refer to as CPUF ("Chirped-Pulse/Uniform flow"). Detection by CPUF requires monitoring the free induction decay (FID) of the rotational coherence. However, the high collision frequency in high-density uniform supersonic flows can interfere with the FID and attenuate the signal. One way to overcome this is to sample the flow, but this can cause interference from shocks in the sampling region. This led us to develop an extended Laval nozzle that creates a uniform flow within the nozzle itself, after which the gas undergoes a shock-free secondary expansion to cold, low pressure conditions ideal for CP-FTmmW detection. Impact pressure measurements, commonly used to characterize Laval flows, cannot be used to monitor the flow within the nozzle. Therefore, we implemented a REMPI (resonance-enhanced multiphoton ionization) detection scheme that allows the interrogation of the conditions of the flow directly inside the extended nozzle, confirming the fluid dynamics simulations of the flow environment. We describe the development of the new 20 K extended flow, along with its characterization using REMPI and computational fluid dynamics. Finally, we demonstrate its application to the first low temperature measurement of the reaction kinetics of HCO with O2 and obtain a rate coefficient at 20 K of 6.66 ± 0.47 × 10-11 cm3 molec-1 s-1.
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Affiliation(s)
- Shameemah Thawoos
- Department of Chemistry, University of Missouri, Columbia, Missouri 65211, USA
| | - Nicolas Suas-David
- Univ Rennes, CNRS, Institut de Physique de Rennes - UMR 6251, F-35000 Rennes, France
| | - Ranil M Gurusinghe
- Department of Chemistry, University of Missouri, Columbia, Missouri 65211, USA
- Department of Chemistry, Tennessee Tech University, Cookeville, Tennessee 38505, USA
| | - Matthew Edlin
- Department of Chemistry, University of Missouri, Columbia, Missouri 65211, USA
| | - Abbas Behzadfar
- Department of Chemistry, University of Missouri, Columbia, Missouri 65211, USA
| | - Jinxin Lang
- Department of Chemistry, University of Missouri, Columbia, Missouri 65211, USA
| | - Arthur G Suits
- Department of Chemistry, University of Missouri, Columbia, Missouri 65211, USA
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Chen TY, Lee YP. Dynamics of the reaction CH 2I + O 2 probed via infrared emission of CO, CO 2, OH and H 2CO. Phys Chem Chem Phys 2020; 22:17540-17553. [PMID: 32808958 DOI: 10.1039/d0cp01940b] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The reaction CH2I + O2 has been widely employed recently for the production of the simplest Criegee intermediate CH2OO in laboratories, but the detailed dynamics of this reaction have been little explored. Infrared emission of several products of this reaction, initiated on irradiation of CH2I2 and O2 (∼8 Torr) in a flowing mixture at 308 or 248 nm, was recorded with a step-scan Fourier-transform spectrometer; possible routes of formation were identified according to the observed vibrational distribution of products and published theoretical potential-energy schemes. Upon irradiation at 308 nm, Boltzmann distributions of CO (v ≤ 5, J ≤ 19) with an average vibrational energy of 32 ± 3 kJ mol-1 and OH (v ≤ 3, J ≤ 5.5) with an average vibrational energy of 29 ± 4 kJ mol-1 were observed and assigned to the decomposition of HCOOH* to form CO + H2O and OH + HCO, respectively. The broadband emission of CO2 was simulated with two vibrational distributions of average energies (91 ± 4) and (147 ± 8) kJ mol-1 and assigned to be produced from the decomposition of HCOOH* and methylene bis(oxy), respectively. Upon irradiation of samples at 248 nm, the emission of OH and CO2 showed similar distributions with slightly greater energies, but the distribution of CO (v ≤ 11, J ≤ 19) became bimodal with average vibrational energies of (23 ± 4) and (107 ± 29) kJ mol-1, and branching (56 ± 5) : (44 ± 5). The additional large-v component is assigned to be produced from a secondary reaction HCO + O2 to form CO + HO2; HCO is a coproduct of OH. The branching between CO and OH is (50 ± 5) : (50 ± 5) at 308 nm and (64 ± 5) : (36 ± 4) at 248 nm, consistent with the mechanism according to which an additional channel to produce CO opens at 248 nm. Highly internally excited H2CO was also observed. With O2 at 16 Torr, the extrapolated nascent internal distributions are similar to those with O2 at 8 Torr except for a slight quenching effect.
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Affiliation(s)
- Ting-Yu Chen
- Department of Applied Chemistry and Institute of Molecular Science National Chiao Tung University, Hsinchu 30010, Taiwan.
| | - Yuan-Pern Lee
- Department of Applied Chemistry and Institute of Molecular Science National Chiao Tung University, Hsinchu 30010, Taiwan. and Center for Emergent Functional Matter Science, National Chiao Tung University, Hsinchu 30010, Taiwan and Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
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Vansco MF, Caravan RL, Zuraski K, Winiberg FAF, Au K, Trongsiriwat N, Walsh PJ, Osborn DL, Percival CJ, Khan MAH, Shallcross DE, Taatjes CA, Lester MI. Experimental Evidence of Dioxole Unimolecular Decay Pathway for Isoprene-Derived Criegee Intermediates. J Phys Chem A 2020; 124:3542-3554. [PMID: 32255634 DOI: 10.1021/acs.jpca.0c02138] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Ozonolysis of isoprene, one of the most abundant volatile organic compounds emitted into the Earth's atmosphere, generates two four-carbon unsaturated Criegee intermediates, methyl vinyl ketone oxide (MVK-oxide) and methacrolein oxide (MACR-oxide). The extended conjugation between the vinyl substituent and carbonyl oxide groups of these Criegee intermediates facilitates rapid electrocyclic ring closures that form five-membered cyclic peroxides, known as dioxoles. This study reports the first experimental evidence of this novel decay pathway, which is predicted to be the dominant atmospheric sink for specific conformational forms of MVK-oxide (anti) and MACR-oxide (syn) with the vinyl substituent adjacent to the terminal O atom. The resulting dioxoles are predicted to undergo rapid unimolecular decay to oxygenated hydrocarbon radical products, including acetyl, vinoxy, formyl, and 2-methylvinoxy radicals. In the presence of O2, these radicals rapidly react to form peroxy radicals (ROO), which quickly decay via carbon-centered radical intermediates (QOOH) to stable carbonyl products that were identified in this work. The carbonyl products were detected under thermal conditions (298 K, 10 Torr He) using multiplexed photoionization mass spectrometry (MPIMS). The main products (and associated relative abundances) originating from unimolecular decay of anti-MVK-oxide and subsequent reaction with O2 are formaldehyde (88 ± 5%), ketene (9 ± 1%), and glyoxal (3 ± 1%). Those identified from the unimolecular decay of syn-MACR-oxide and subsequent reaction with O2 are acetaldehyde (37 ± 7%), vinyl alcohol (9 ± 1%), methylketene (2 ± 1%), and acrolein (52 ± 5%). In addition to the stable carbonyl products, the secondary peroxy chemistry also generates OH or HO2 radical coproducts.
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Affiliation(s)
- Michael F Vansco
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, United States
| | - Rebecca L Caravan
- NASA Postdoctoral Program, NASA Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109, United States.,Combustion Research Facility, Sandia National Laboratories, Mailstop 9055, Livermore, California 94551, United States.,Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Kristen Zuraski
- NASA Postdoctoral Program, NASA Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109, United States
| | - Frank A F Winiberg
- NASA Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109, United States.,California Institute of Technology, Pasadena, California 91125, United States
| | - Kendrew Au
- Combustion Research Facility, Sandia National Laboratories, Mailstop 9055, Livermore, California 94551, United States
| | - Nisalak Trongsiriwat
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, United States
| | - Patrick J Walsh
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, United States
| | - David L Osborn
- Combustion Research Facility, Sandia National Laboratories, Mailstop 9055, Livermore, California 94551, United States
| | - Carl J Percival
- NASA Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109, United States.,California Institute of Technology, Pasadena, California 91125, United States
| | - M Anwar H Khan
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| | - Dudley E Shallcross
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| | - Craig A Taatjes
- Combustion Research Facility, Sandia National Laboratories, Mailstop 9055, Livermore, California 94551, United States
| | - Marsha I Lester
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, United States
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Mai TVT, Duong MV, Nguyen HT, Huynh LK. Ab initio kinetics of the HOSO 2 + 3O 2 → SO 3 + HO 2 reaction. Phys Chem Chem Phys 2018; 20:6677-6687. [PMID: 29457181 DOI: 10.1039/c7cp07704a] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The detailed kinetic mechanism of the HOSO2 + 3O2 reaction, which plays a pivotal role in the atmospheric oxidation of SO2, was investigated using accurate electronic structure calculations and novel statistical thermodynamic/kinetic models. Explored using the accurate composite method W1U, the detailed potential energy surface (PES) revealed that the addition of O2 to a HOSO2 radical to form the adduct (HOSO4) proceeds via a transition state with a slightly positive barrier (i.e., 0.7 kcal mol-1 at 0 K). Such a finding compromises a long-term hypothesis about this channel of being a barrierless process. Moreover, the overall reaction was found to be slightly exothermic by 1.7 kcal mol-1 at 0 K, which is in good agreement with recent studies. On the newly-constructed PES, the temperature- and pressure-dependent behaviors of the title reaction were characterized in a wide range of conditions (T = 200-1000 K & P = 10-760 Torr) using the integrated deterministic and stochastic master equation/Rice-Ramsperger-Kassel-Marcus (ME/RRKM) rate model in which corrections for hindered internal rotation (HIR) and tunneling treatments were included. The calculated numbers were found to be in excellent agreement with literature data. The sensitivity analyses on the derived rate coefficients with respect to the ab initio input parameters (i.e., barrier height and energy transfer) were also performed to further understand the kinetic behaviors of the title reaction. The detailed kinetic mechanism, consisting of thermodynamic and kinetic data (in NASA polynomial and modified Arrhenius formats, respectively), was also provided at different T & P for further use in the modeling/simulation of any related systems.
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Affiliation(s)
- Tam V-T Mai
- Molecular Science and Nano-Materials Lab, Institute for Computational Science and Technology, SBI Building, Quang Trung Software City, Tan Chanh Hiep Ward, District 12, Ho Chi Minh City, Vietnam
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Bao JL, Truhlar DG. Silane-initiated nucleation in chemically active plasmas: validation of density functionals, mechanisms, and pressure-dependent variational transition state calculations. Phys Chem Chem Phys 2016; 18:10097-108. [DOI: 10.1039/c6cp00816j] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Pressure-dependent rate constants for nucleation in nanodusty plasmas are calculated by variational transition state theory with system-specific quantum RRK theory.
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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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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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Asgharzade S, Vahedpour M. Mechanism and Thermodynamics of Multichannel 1:1 Ammonia and Ozone Tropospheric Oxidation Reaction. PROGRESS IN REACTION KINETICS AND MECHANISM 2013. [DOI: 10.3184/146867813x13738207456659] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The reaction of NH3 + O3 on the singlet potential energy surface has been investigated theoretically using CCSD(T) and G3B3 methods with the 6-311++G(3df,3pd) basis set based on the geometric parameters optimised at the B3LYP/6-311++G(3df,3pd) level of theory. The calculated results revealed that the reactants are firstly associated with the adduct NH3–O3, through a barrier-less process and two stable collision complexes, C1 and C2 have been considered. Six kinds of products P1 (HOO + H2NO), P2 (OH + H2NO2), P3 (O2 + H3NO), P4 (HNO + H2O2), P5 (HNO2 + H2O) and P6 (NO + HO2 + H2) are obtained through a variety of transformations of C1 and C2. Thermodynamic parameters of all possible products show five production channels which are spontaneous. After taking into account the reaction barrier and enthalpy, the most probable reaction pathways are P1(2) and P4. Also, P4 is the most stable product in comparison with the others and P1 yields the other important products from the kinetic viewpoint; this is relatively stable, with a negative Gibbs free energy. Branching ratio results show P1 is the major product at low temperature. Finally, the rates constant have been computed only for the P1(2) and P4 pathways by related theories in the temperature range of 200–2500 K.
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Affiliation(s)
- Somaie Asgharzade
- Department of Chemistry, University of Zanjan, Zanjan 45371-38791, Iran
| | - Morteza Vahedpour
- Department of Chemistry, University of Zanjan, Zanjan 45371-38791, Iran
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8
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Association reaction between SiH3 and H2O2: a computational study of the reaction mechanism and kinetics. Theor Chem Acc 2013. [DOI: 10.1007/s00214-013-1375-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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9
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Flisak Z. Thermodynamics of Titanium and Vanadium Reduction in Non-Aqueous Environment Calculated at Various Levels of Theory. J Phys Chem A 2012; 116:1464-8. [DOI: 10.1021/jp211690y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Zygmunt Flisak
- Faculty of Chemistry, University of Opole, Oleska 48, 45-052 Opole, Poland
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XIE HONGBIN, DING YIHONG, SUN CHIACHUNG. RADICAL-MOLECULE REACTIONS HCO/HOC + C2H4: A MECHANISTIC STUDY. JOURNAL OF THEORETICAL & COMPUTATIONAL CHEMISTRY 2011. [DOI: 10.1142/s0219633605001994] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
A detailed computational study is performed on the radical-molecule reactions between HCO/HOC and ethylene ( C 2 H 4) at the Gaussian-3//B3LYP/6-31G(d) level. For the HCO + C 2 H 4 reaction, the most favorable pathway is the direct C -addition forming the intermediate H 2 CCH 2 CHO , followed by a 1,2- H -shift leading to H 3 CCHCHO . Subsequently, there are two highly competitive dissociation pathways for H 3 CCHCHO : one is the formation of the direct H -extrusion product H 2 CCHCHO + H , and the other is the formation of C 2 H 5 + CO via the intermediate H 3 CCH 2 CO . The overall reaction barrier is 14.1 and 14.6 kcal/mol respectively, at the G3B3 level. The quasi-direct H -donation process to produce C 2 H 5 + CO with the barrier 16.5 kcal/mol is less competitive. Thus, only at higher temperatures, the HCO + C 2 H 4 reaction could play a role. In contrast, the HOC + C 2 H 4 reaction just need to overcome a small barrier 2.0 kcal/mol to generate C 2 H 5 + CO via the quasi-direct H -donation mechanism. This is suggestive of the potential importance of the HOC + C 2 H 4 reaction in combustion processes. However, the direct C -addition channel is much less competitive. The present kinetic data and orbital analysis show that the HCO radical has much higher reactivity than HOC , although the latter is more energetic. Till now, no kinetic study on the HOC radical has been reported, the present study can provide useful information on understanding the reactivity and depletion mechanism of the energetic HOC radical.
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Affiliation(s)
- HONG-BIN XIE
- State Key Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun 130023, People's Republic of China
| | - YI-HONG DING
- State Key Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun 130023, People's Republic of China
| | - CHIA-CHUNG SUN
- State Key Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun 130023, People's Republic of China
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Alecu IM, Truhlar DG. Computational Study of the Reactions of Methanol with the Hydroperoxyl and Methyl Radicals. 1. Accurate Thermochemistry and Barrier Heights. J Phys Chem A 2011; 115:2811-29. [PMID: 21405059 DOI: 10.1021/jp110024e] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- I. M. Alecu
- Department of Chemistry and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, United States
| | - Donald G. Truhlar
- Department of Chemistry and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, United States
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Alam MS, Camredon M, Rickard AR, Carr T, Wyche KP, Hornsby KE, Monks PS, Bloss WJ. Total radical yields from tropospheric ethene ozonolysis. Phys Chem Chem Phys 2011; 13:11002-15. [DOI: 10.1039/c0cp02342f] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Antiñolo M, Jiménez E, Albaladejo J. UV absorption cross sections between 230 and 350 nm and pressure dependence of the photolysis quantum yield at 308 nm of CF3CH2CHO. Phys Chem Chem Phys 2011; 13:15936-46. [DOI: 10.1039/c1cp21368g] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Christiansen CJ, Francisco JS. Atmospheric Oxidation of Trichloroethylene: An Ab Initio Study. J Phys Chem A 2010; 114:9163-76. [PMID: 20687539 DOI: 10.1021/jp103769z] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- Carrie J. Christiansen
- Department of Chemistry and Department of Earth and Atmospheric Sciences Purdue University, West Lafayette, Indiana 47909
| | - Joseph S. Francisco
- Department of Chemistry and Department of Earth and Atmospheric Sciences Purdue University, West Lafayette, Indiana 47909
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Christiansen CJ, Francisco JS. Atmospheric Oxidation of Tetrachloroethylene: An Ab Initio Study. J Phys Chem A 2010; 114:9177-91. [PMID: 20669984 DOI: 10.1021/jp103845h] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Carrie J. Christiansen
- Department of Chemistry and Department of Earth and Atmospheric Sciences Purdue University, West Lafayette, Indiana 47909
| | - Joseph S. Francisco
- Department of Chemistry and Department of Earth and Atmospheric Sciences Purdue University, West Lafayette, Indiana 47909
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Lambert N, Kaltsoyannis N, Price SD, Zabka J, Herman Z. Bond-forming reactions of dications with molecules: a computational and experimental study of the mechanisms for the formation of HCF2+ from CF3(2+) and H2. J Phys Chem A 2007; 110:2898-905. [PMID: 16509611 DOI: 10.1021/jp052981d] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The QCISD and QCISD(T) quantum chemical methods have been used to characterize the energetics of various possible mechanisms for the formation of HCF2+ from the bond-forming reaction of CF3(2+) with H2. The stationary points on four different pathways leading to the product combinations HCF2+ + H+ + F and HCF2+ + HF+ have been calculated. All four pathways begin with the formation of a collision complex [H2-CF3]2+, followed by an internal hydrogen atom migration to give HC(FH)F2(2+). In two of the mechanisms, immediate charge separation of HC(FH)F2(2+) via loss of either HF+ or a proton, followed by loss of an F atom, yields the experimentally observed bond-forming product HCF2+. For the other two mechanisms, internal hydrogen rearrangement of HC(FH)F2(2+) to give C(FH)2F(2+), followed by charge separation, yields the product CF2H+. This product can then overcome a 2.04 eV barrier to rearrange to the HCF2+ isomer, which is 1.80 eV more stable. All four calculated mechanisms are in agreement with the isotope effects and collision energy dependencies of the product ion cross sections that have been previously observed experimentally following collisions between CF3(2+) and H2/D2. We find that in this open-shell system, CCSD(T) and QCISD(T) T1-diagnostic values of up to 0.04 are acceptable. A series of angularly resolved crossed-beam scattering experiments on collisions of CF3(2+) with D2 have also been performed. These experiments show two distinct channels leading to the formation of DCF2+. One channel appears to correspond to the pathway leading to the ground state 1DCF2+ + D+ + F product asymptote and the other to the 3DCF2+ + D+ + F product asymptote, which is 5.76 eV higher in energy. The experimental kinetic energy releases for these channels, 7.55 and 1.55 eV respectively, have been determined from the velocities of the DCF2+ product ion and are in agreement with the reaction mechanisms calculated quantum chemically. We suggest that both of these observed experimental channels are governed by the reaction mechanism we calculate in which charge separation occurs first by loss of a proton, without further hydrogen atom rearrangement, followed by loss of an F atom to give the final products 1DCF2+ + D+ + F or 3DCF2+ + D+ + F.
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Affiliation(s)
- Natalie Lambert
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK
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Dong H, Ding YH, Sun CC. Radical−Molecule Reactions HCO/HOC + C2H2: Mechanistic Study. J Phys Chem A 2005; 109:11941-55. [PMID: 16366647 DOI: 10.1021/jp0442854] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A detailed computational study is performed on the unknown radical-molecule reactions between HCO/HOC and acetylene (C2H2) at the CCSD(T)/6-311G(2d,p)//B3LYP/6-311G(d,p)+ZPVE, Gaussian-3//B3LYP/6-31G(d), and Gaussian-3//MP2(full)/6-31G(d) levels. For the HCO + C2H2 reaction, the most favorable pathway is direct C-addition forming the intermediate HC=CHCH=O followed by a 1,3-H-shift leading to H2C=CHC=O, which finally dissociates to the product C2H3 + CO. The overall reaction barrier is 13.8, 10.5, and 11.3 kcal/mol, respectively, at the three levels. The quasi-direct H-donation process to produce C2H3 + CO with barriers of 14.0, 14.1, and 14.1 kcal/mol is less competitive. Thus only at higher temperatures could the HCO + C2H2 reaction play a role. In contrast, the HOC + C2H2 reaction can barrierlessly generate C2H3 + CO via the quasi-direct H-donation mechanism proceeding via a prereactive complex with OH...C2 hydrogen bonding. This is suggestive of the potential importance of the HOC + C2H2 reaction in both combustion and interstellar processes. However, the direct C-addition channel is much less competitive. For both reactions, the possible formation of the intriguing interstellar molecules propadiene and propynal is also discussed. The present theoretical study represents the first attempt to probe the reaction mechanism between HOC and pi-systems. Future laboratory investigations on both reactions (particularly HOC + C2H2) are recommended.
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Affiliation(s)
- Hao Dong
- State Key Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun 130023, People's Republic of China
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Dong H, Ding YH, Sun CC. Mechanism of HCS + O2 reaction: Hydrogen- or oxygen-transfer? Phys Chem Chem Phys 2005; 7:3711-5. [PMID: 16358018 DOI: 10.1039/b508904b] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
In spite of the potential importance of the HCS radical in both combustion and interstellar processes, its chemical reactivity has not been tackled previously. In the present paper, the oxidation reaction of the HCS radical is theoretically investigated for the first time at the CCSD(T)/6-311++G(3df,2p)//BH&HLYP/6-311++G(d,p)+ZPVE and Gaussian-3//B3LYP/6-31G(d) levels. It is shown that the most feasible pathway is the O2 addition to the HCS radical forming the intermediate SC(H)OO which can undergo a subsequent O-extrusion leading to SC(H)O + 3O. This features an indirect O-transfer mechanism with the overall barrier of 4.4 and 3.5 kcal mol(-1), respectively, at the two levels. However, formation of the H-transfer product CS + HO2 is kinetically much less feasible, i.e., the direct mechanism has barriers of 14.3 and 8.7 kcal mol(-1), whereas the indirect mechanism has barriers of 12.6 and 10.7 kcal mol(-1), respectively. This result is in sharp contrast to the analogous HCO + O2 reaction, where the direct (with a barrier of 2.98 kcal mol(-1)) and indirect (2.26 kcal mol(-1)) H-transfer processes are highly competitive over the indirect O-transfer process (the least endothermicity is 19.9 kcal mol(-1)). The possible explanations and implications of the present results are provided.
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Affiliation(s)
- Hao Dong
- State Key Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun, 130023, People's Republic of China
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