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Combustion inhibition of cup-burner flame with C2HF3Cl2 and its kinetics mechanism investigation. Chem Phys Lett 2022. [DOI: 10.1016/j.cplett.2022.140275] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Theoretical Kinetic and Mechanistic Studies on the Reactions of CF₃CBrCH₂ (2-BTP) with OH and H Radicals. Molecules 2017; 22:molecules22122140. [PMID: 29210996 PMCID: PMC6150020 DOI: 10.3390/molecules22122140] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Revised: 11/24/2017] [Accepted: 11/29/2017] [Indexed: 11/24/2022] Open
Abstract
CF3CBrCH2 (2-bromo-3,3,3-trifluoropropene, 2-BTP) is a potential replacement for CF3Br; however, it shows conflicted inhibition and enhancement behaviors under different combustion conditions. To better understand the combustion chemistry of 2-BTP, a theoretical study has been performed on its reactions with OH and H radicals. Potential energy surfaces were exhaustively explored by using B3LYP/aug-cc-pVTZ for geometry optimizations and CCSD(T)/aug-cc-pVTZ for high level single point energy refinements. Detailed kinetics of the major pathways were predicted by using RRKM/master-equation methodology. The present predictions imply that the –C(Br)=CH2 moiety of 2-BTP is most likely to be responsible for its fuel-like property. For 2-BTP + OH, the addition to the initial adduct (CF3CBrCH2OH) is the dominant channel at low temperatures, while the substitution reaction (CF3COHCH2 + Br) and H abstraction reaction (CF3CBrCH + H2O) dominates at high temperatures and elevated pressures. For 2-BTP + H, the addition to the initial adduct (CF3CBrCH3) also dominates the overall kinetics at low temperatures, while Br abstraction reaction (CF3CCH2 + HBr) and β-scission of the adduct forming CF3CHCH2 + Br dominates at high temperatures and elevated pressures. Compared to 2-BTP + OH, the 2-BTP + H reaction tends to have a larger effect on flame suppression, given the fact that it produces more inhibition species.
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Duncan JR, Roach MS, Stiles BS, Holmes BE. Unimolecular rate constant and threshold energy for the HF elimination from chemically activated CF3CHFCF3. J Phys Chem A 2010; 114:6996-7002. [PMID: 20536197 DOI: 10.1021/jp100195e] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Combination of CF(3)CHF and CF(3) radicals at room temperature generated chemically activated CF(3)CHFCF(3) molecules with 95 +/- 3 kcal/mol of internal energy that decompose by loss of HF, initially attached to adjacent carbons, with an experimental unimolecular rate constant of (4.5 +/- 1.1) x 10(2) s(-1). Density functional theory was used to model the unimolecular rate constant for HF elimination, k(HF), to determine a threshold energy of 75 +/- 2 kcal/mol.
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Affiliation(s)
- Juliana R Duncan
- Department of Chemistry, University of North Carolina at Asheville, One University Heights, Asheville, North Carolina 28804-8511, USA
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Mok DKW, Chau FT, Lee EPF, Dyke JM. High-level ab initio calculations on HGeCl and the equilibrium geometry of the A1A'' state derived from Franck-Condon analysis of the single-vibronic-level emission spectra of HGeCl and DGeCl. J Comput Chem 2009; 31:476-91. [PMID: 19499544 DOI: 10.1002/jcc.21331] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
CCSD(T) and/or CASSCF/MRCI calculations have been carried out on the X(1)A' and A(1)A'' states of HGeCl. The fully relativistic effective core potential, ECP10MDF, and associated standard valence basis sets of up to the aug-cc-pV5Z quality were employed for Ge. Contributions from core correlation and extrapolation to the complete basis set limit were included in determining the computed equilibrium geometrical parameters and relative electronic energy of these two states of HGeCl. Based on the currently, most systematic CCSD(T) calculations performed in this study, the best theoretical geometrical parameters of the X(1)A' state are r(e)(HGe) = 1.580 +/- 0.001 A, theta(e) = 93.88 +/- 0.01 degrees and r(e)(GeCl) = 2.170 +/- 0.001 A. In addition, Franck-Condon factors including allowance for anharmonicity and Duschinsky rotation between these two states of HGeCl and DGeCl were calculated employing CCSD(T) and CASSCF/MRCI potential energy functions, and were used to simulate A(1)A'' --> X(1)A' SVL emission spectra of HGeCl and DGeCl. The iterative Franck-Condon analysis (IFCA) procedure was carried out to determine the equilibrium geometrical parameters of the A(1)A'' state of HGeCl by matching the simulated, and available experimental SVL emission spectra of HGeCl and DGeCl of Tackett et al., J Chem Phys 2006, 124, 124320, using the available, estimated experimental equilibrium (r(e)(z)) structure for the X(1)A' state, while varying the equilibrium geometrical parameters of the A(1)A'' state systematically. Employing the derived IFCA geometry of r(e)(HGe) = 1.590 A, r(e)(GeCl) = 2.155 A and theta(e)(HGeCl) = 112.7 degrees for the A(1)A'' state of HGeCl in the spectral simulation, the simulated absorption and SVL emission spectra of HGeCl and DGeCl agree very well with the available experimental LIF and SVL emission spectra, respectively.
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Affiliation(s)
- Daniel K W Mok
- Department of Applied Biology and Chemical Technology, the Hong Kong Polytechnic University, Hung Hom, Hong Kong.
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Mok DWK, Lee EPF, Chau FT, Dyke JM. Franck−Condon Simulations including Anharmonicity of the Ã1A′′−X̃1A′ Absorption and Single Vibronic Level Emission Spectra of HSiCl and DSiCl. J Chem Theory Comput 2009; 5:565-79. [DOI: 10.1021/ct800513v] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Daniel W. K. Mok
- Department of Applied Biology and Chemical Technology, the Hong Kong Polytechnic University, Hung Hom, Hong Kong, and School of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, U.K
| | - Edmond P. F. Lee
- Department of Applied Biology and Chemical Technology, the Hong Kong Polytechnic University, Hung Hom, Hong Kong, and School of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, U.K
| | - Foo-tim Chau
- Department of Applied Biology and Chemical Technology, the Hong Kong Polytechnic University, Hung Hom, Hong Kong, and School of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, U.K
| | - John M. Dyke
- Department of Applied Biology and Chemical Technology, the Hong Kong Polytechnic University, Hung Hom, Hong Kong, and School of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, U.K
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Lee EPF, Dyke JM, Mok DKW, Chow WK, Chau FT. Ab initio calculations on low-lying electronic states of SnCl2−and Franck–Condon simulation of its photodetachment spectrum. Phys Chem Chem Phys 2008; 10:834-43. [DOI: 10.1039/b715595f] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Lee EPF, Mok DKW, Chau FT, Dyke JM. Ab initio calculations on the X̃A′1 and ÃA″1 states of HPO and Franck-Condon simulation of the single vibronic level emission spectra of HPO and DPO. J Chem Phys 2007; 127:214305. [DOI: 10.1063/1.2790892] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Lee EPF, Dyke JM, Chow WK, Chau FT, Mok DKW. DFT and ab initio
calculations on two reactions between hydrogen atoms and the fire suppressants 2-H heptafluoropropane and CF3
Br. J Comput Chem 2007; 28:1582-1592. [PMID: 17340604 DOI: 10.1002/jcc.20695] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Reaction enthalpies and barrier heights of the reactions CF3Br+H-->CF3+HBr {reaction (1)} and CF3CHFCF3+H-->CF3CFCF3+H2 {reaction (2)} have been calculated at the near state-of-the-art ab initio level, and also by employing the B3LYP, BH&HLYP, BB1K, MPW1K, MPWB1K and TPSS1KCIS functionals. In addition, the integrated molecular orbital+molecular orbital (IMOMO) method has been used to study reaction (2). The ab initio benchmark values of the reaction enthalpy (298 K) and barrier height (0 K) of reaction (2) are reported for the first time {-(0.7+/-0.7) and 13.3+/-0.5 kcal/mole respectively}. When density functional theory (DFT) results are compared with ab initio benchmarks for both reactions (1) and (2), the MPWB1K functional is found to have the best performance of the six functionals used. The IMOMO method with the RCCSD/aug-cc-pVTZ and/or RCCSD(T)/aug-cc-pVTZ levels, as the high levels of calculation on the model system, gives reaction enthalpies and barrier heights of reaction (2), which agree with ab initio benchmark values to within 1 kcal/mole. Computed key geometrical parameters and imaginary vibrational frequencies of the transition state structures of reactions (1) and (2) obtained at different levels of calculation are compared. The magnitudes of the computed imaginary vibrational frequencies of the transition states of both reactions considered are found to be very sensitive to the levels of calculation used to obtain them. The heat of formation (298 K) of CF3CFCF3 calculated at the near state-of-the-art level has a value of -(318+/-3) kcal/mole.
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Affiliation(s)
- Edmond P F Lee
- Department of Building Services Engineering, The Hong Kong Polytechnic University, Hung Hom, Hong Kong
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Hong Kong
- School of Chemistry, University of Southampton, Highfield, Southampton, SO17 1BJ United Kingdom
| | - John M Dyke
- School of Chemistry, University of Southampton, Highfield, Southampton, SO17 1BJ United Kingdom
| | - Wan-Ki Chow
- Department of Building Services Engineering, The Hong Kong Polytechnic University, Hung Hom, Hong Kong
| | - Foo-Tim Chau
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Hong Kong
| | - Daniel K W Mok
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Hong Kong
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Mok DKW, Chau FT, Lee EPF, Dyke JM. Ab initiocalculations on SCl2 and low-lying cationic states of SCl2+: Franck-Condon simulation of the UV photoelectron spectrum of SCl2. J Chem Phys 2006; 125:104303. [PMID: 16999522 DOI: 10.1063/1.2202734] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Geometry optimization calculations were carried out on the (approximate)X (1)A(1) state of SCl(2) and the (approximate)X(2)B(1), (approximate)A(2)B(2), (approximate)B(2)A(1), (approximate)C(2)A(1), (approximate)D(2)A(2), and (approximate)E (2)B(2) states of SCl(2) (+) at the restricted-spin coupled-cluster single-double plus perturbative triple excitation [RCCSD(T)] level with basis sets of up to the augmented correlation-consistent polarized quintuple-zeta [aug-cc-pV(5+d)Z] quality. Effects of core electron correlation, basis set extension to the complete basis set limit, and relativistic contributions on computed minimum-energy geometrical parameters and/or relative electronic energies were also investigated. RCCSD(T) potential energy functions (PEFs) were calculated for the (approximate)X (1)A(1) state of SCl(2) and the low-lying states of SCl(2)(+) listed above employing the aug-cc-pV(5+d)Z basis set. Anharmonic vibrational wave functions of these neutral and cationic states of SCl(2), and Franck-Condon (FC) factors of the lowest four one-electron allowed neutral photoionizations were computed employing the RCCSD(T)aug-cc-pV(5+d)Z PEFs. Calculated FC factors with allowance for the Duschinsky rotation and anharmonicity were used to simulate the first four photoelectron (PE) bands of SCl(2). The agreement between simulated and observed He I PE spectra reported by Colton et al. [J. Electron Spectrosc. Relat. Phenom. 3, 345 (1974)] and Solouki et al. [Chem. Phys. Lett. 26, 20 (1974)] is excellent. However, our FC spectral simulations indicate that the first observed vibrational component in the first PE band of SCl(2) is a "hot" band arising from the SCl(2)(+)(approximate)X(2)B(1)(0,0,0)<--SCl(2)(approximate)X (1)A(1)(1,0,0) ionization. Consequently, the experimental adiabatic ionization energy of SCl(2) is revised to 9.55+/-0.01 eV, in excellent agreement with results obtained from state-of-the-art ab initio calculations in this work.
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Affiliation(s)
- Daniel K W Mok
- Department of Applied Biology and Chemical Technology, Hong Kong Polytechnic University, Hung Hom, Hong Kong.
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Lee EPF, Mok DKW, Chau FT, Dyke JM. Ab initio calculations on SF2 and its low-lying cationic states: anharmonic Franck-Condon simulation of the UV photoelectron spectrum of SF2. J Chem Phys 2006; 125:104304. [PMID: 16999523 DOI: 10.1063/1.2227380] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Geometry optimization calculations were carried out on the (approximate)X(1)A(1) state of SF2 and the (approximate)X(2)B(1), (approximate)A(2)A(1), (approximate)B(2)B(2), (approximate)C(2)B(2), (approximate)D(2)A(1), and (approximate)E(2)A(2) states of SF2(+) employing the restricted-spin coupled-cluster single-double plus perturbative triple excitation [RCCSD(T)] method and basis sets of up to the augmented correlation-consistent polarized quintuple-zeta [aug-cc-pV(5+d)Z] quality. Effects of core electron (S 2s(2)2p(6) and F 1s(2) electrons) correlation and basis set extension to the complete basis set limit on the computed minimum-energy geometries and relative electronic energies (adiabatic and vertical ionization energies) were investigated. RCCSD(T) potential energy functions (PEFs) were calculated for the (approximate)X(1)A(1) state of SF2 and the low-lying states of SF2(+) listed above employing the aug-cc-pV(5+d)Z and aug-cc-pV5Z basis sets for S and F, respectively. Anharmonic vibrational wave functions of these neutral and cationic states of SF2, and Franck-Condon (FC) factors of the lowest four one-electron allowed neutral photoionizations were computed employing the RCCSD(T) PEFs. Calculated FC factors with allowance for Duschinsky rotation and anharmonicity were used to simulate the first four photoelectron bands of SF2. The agreement between the simulated and observed first bands in the He I photoelectron spectrum reported by de Leeuw et al. [Chem. Phys. 34, 287 (1978)] is excellent. Our calculations largely support assignments made by de Leeuw et al. on the higher ionization energy bands of SF2.
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Affiliation(s)
- Edmond P F Lee
- Department of Applied Biology and Chemical Technology, Hong Kong Polytechnic University, Hung Hom, Hong Kong.
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Lee E, Dyke J, Chow WK, Chau FT, Mok D. DFT and ab initio calculations on the reaction between fluorine atoms and the fire suppressant, 2-H heptafluoropropane. Chem Phys Lett 2006. [DOI: 10.1016/j.cplett.2005.10.013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Lee E, Dyke J, Chow WK, Chau FT, Mok D. The heat of formation of 2-H heptafluoropropane by ab initio calculations. Chem Phys Lett 2005. [DOI: 10.1016/j.cplett.2004.12.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Oren M, Iron MA, Burcat A, Martin JML. Thermodynamic Properties of C1 and C2 Bromo Compounds and Radicals. A Relativistic ab Initio Study. J Phys Chem A 2004. [DOI: 10.1021/jp0475786] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Mikhal Oren
- Department Of Organic Chemistry, Weizmann Institute of Science, Rehovot, 76100 Israel, and The Faculty of Aerospace Engineering, Technion-Israel Institute of Technology, Haifa, 32000 Israel
| | - Mark A. Iron
- Department Of Organic Chemistry, Weizmann Institute of Science, Rehovot, 76100 Israel, and The Faculty of Aerospace Engineering, Technion-Israel Institute of Technology, Haifa, 32000 Israel
| | - Alexander Burcat
- Department Of Organic Chemistry, Weizmann Institute of Science, Rehovot, 76100 Israel, and The Faculty of Aerospace Engineering, Technion-Israel Institute of Technology, Haifa, 32000 Israel
| | - Jan M. L. Martin
- Department Of Organic Chemistry, Weizmann Institute of Science, Rehovot, 76100 Israel, and The Faculty of Aerospace Engineering, Technion-Israel Institute of Technology, Haifa, 32000 Israel
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