DFT and ab initio calculations on two reactions between hydrogen atoms and the fire suppressants 2-H heptafluoropropane and CF3Br

Copyright (c) 2007 Wiley Periodicals, Inc.

Bibliographische Detailangaben
Veröffentlicht in:Journal of computational chemistry. - 1984. - 28(2007), 9 vom: 15. Juli, Seite 1582-1592
1. Verfasser: Lee, Edmond P F (VerfasserIn)
Weitere Verfasser: Dyke, John M, Chow, Wan-Ki, Chau, Foo-Tim, Mok, Daniel K W
Format: Online-Aufsatz
Sprache:English
Veröffentlicht: 2007
Zugriff auf das übergeordnete Werk:Journal of computational chemistry
Schlagworte:Journal Article Research Support, Non-U.S. Gov't Bromochlorofluorocarbons Chlorofluorocarbons, Methane Hydrocarbons, Fluorinated bromotrifluoromethane 52231LCA7R Hydrogen 7YNJ3PO35Z apaflurane R40P36GDK6
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100 1 |a Lee, Edmond P F  |e verfasserin  |4 aut 
245 1 0 |a DFT and ab initio calculations on two reactions between hydrogen atoms and the fire suppressants 2-H heptafluoropropane and CF3Br 
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520 |a 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 
650 4 |a Journal Article 
650 4 |a Research Support, Non-U.S. Gov't 
650 7 |a Bromochlorofluorocarbons  |2 NLM 
650 7 |a Chlorofluorocarbons, Methane  |2 NLM 
650 7 |a Hydrocarbons, Fluorinated  |2 NLM 
650 7 |a bromotrifluoromethane  |2 NLM 
650 7 |a 52231LCA7R  |2 NLM 
650 7 |a Hydrogen  |2 NLM 
650 7 |a 7YNJ3PO35Z  |2 NLM 
650 7 |a apaflurane  |2 NLM 
650 7 |a R40P36GDK6  |2 NLM 
700 1 |a Dyke, John M  |e verfasserin  |4 aut 
700 1 |a Chow, Wan-Ki  |e verfasserin  |4 aut 
700 1 |a Chau, Foo-Tim  |e verfasserin  |4 aut 
700 1 |a Mok, Daniel K W  |e verfasserin  |4 aut 
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