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Ab initio calculations for hydrocarbons : enthalpy of formation, transition state geometry, and activation energy for radical reactions

(2003) JOURNAL OF PHYSICAL CHEMISTRY A. 107(43). p.9147-9159
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Abstract
A quantum chemical investigation is presented for the determination of accurate kinetic and thermodynamic parameters for hydrocarbon radical reactions. First, standard enthalpies of formation are calculated at different levels of theory for a training set of 5 8 hydrocarbon molecules, ranging from C I to C 10, for which experimental data are available. It is found that the CBS-QB3 method succeeds in predicting standard enthalpies of formation with a mean absolute deviation of 2.5 kJ/mol, after a systematic correction of -1.29 kJ/mol per carbon atom and -0.28 kJ/mol per hydrogen atom. Even after a systematic correction, B3LYP density functional theory calculations are not able to reach this accuracy, with mean absolute deviations of 9.2 (B3LYP/6-31G(d)) and 12.9 kJ/mol (B3LYP/6-311G(d,p)), and with increasing deviations for larger hydrocarbons. Second, high-level transition state geometries are determined for 9 carbon-centered radical additions and 6 hydrogen additions to alkenes and alkynes and 10 hydrogen abstraction reactions using the IRCMax(CBS-QB3//B3LYP/6-311G(d,p)) method. For carbon-centered radical addition reactions, B3LYP/6-311G(d,p) slightly overestimates the length of the forming C-C bond as compared to the IRCMax data. A correlation to improve the agreement is proposed. For hydrogen addition reactions, MPW1K density functional theory (MPW1K/6-31G(d)) is able to locate transition states. However, the lengths of the forming C-H bonds are systematically longer than reference IRCMax data. Here, too, a correlation is proposed to improve the agreement. Transition state geometries for hydrogen abstraction reactions obtained with B3LYP/6-311G(d,p) show good agreement with the IRCMax reference data. Third, the improved transition state geometries are used to calculate activation energies at the CBS-QB3 level. Comparison between both CBS-QB3 and B3LYP density functional theory predictions shows deviations up to 25 kJ/mol. Although main trends are captured by B3LYP DFT, secondary trends due to radical nucleophilic effects are not reproduced accurately.
Keywords
DENSITY-FUNCTIONAL THEORY, HYDROGEN ABSTRACTION REACTION, SET MODEL CHEMISTRY, BOND-DISSOCIATION ENERGIES, REACTION-RATE PREDICTION, GROUP ADDITIVITY, RATE CONSTANTS, THEORETICAL PROCEDURES, SUBSTITUTED ALKENES, HARTREE-FOCK

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Chicago
Saeys, Mark, Marie-Françoise Reyniers, Guy Marin, Veronique Van Speybroeck, and Michel Waroquier. 2003. “Ab Initio Calculations for Hydrocarbons : Enthalpy of Formation, Transition State Geometry, and Activation Energy for Radical Reactions.” Journal of Physical Chemistry A 107 (43): 9147–9159.
APA
Saeys, Mark, Reyniers, M.-F., Marin, G., Van Speybroeck, V., & Waroquier, M. (2003). Ab initio calculations for hydrocarbons : enthalpy of formation, transition state geometry, and activation energy for radical reactions. JOURNAL OF PHYSICAL CHEMISTRY A, 107(43), 9147–9159.
Vancouver
1.
Saeys M, Reyniers M-F, Marin G, Van Speybroeck V, Waroquier M. Ab initio calculations for hydrocarbons : enthalpy of formation, transition state geometry, and activation energy for radical reactions. JOURNAL OF PHYSICAL CHEMISTRY A. 2003;107(43):9147–59.
MLA
Saeys, Mark, Marie-Françoise Reyniers, Guy Marin, et al. “Ab Initio Calculations for Hydrocarbons : Enthalpy of Formation, Transition State Geometry, and Activation Energy for Radical Reactions.” JOURNAL OF PHYSICAL CHEMISTRY A 107.43 (2003): 9147–9159. Print.
@article{348744,
  abstract     = {A quantum chemical investigation is presented for the determination of accurate kinetic and thermodynamic parameters for hydrocarbon radical reactions. First, standard enthalpies of formation are calculated at different levels of theory for a training set of 5 8 hydrocarbon molecules, ranging from C I to C 10, for which experimental data are available. It is found that the CBS-QB3 method succeeds in predicting standard enthalpies of formation with a mean absolute deviation of 2.5 kJ/mol, after a systematic correction of -1.29 kJ/mol per carbon atom and -0.28 kJ/mol per hydrogen atom. Even after a systematic correction, B3LYP density functional theory calculations are not able to reach this accuracy, with mean absolute deviations of 9.2 (B3LYP/6-31G(d)) and 12.9 kJ/mol (B3LYP/6-311G(d,p)), and with increasing deviations for larger hydrocarbons. Second, high-level transition state geometries are determined for 9 carbon-centered radical additions and 6 hydrogen additions to alkenes and alkynes and 10 hydrogen abstraction reactions using the IRCMax(CBS-QB3//B3LYP/6-311G(d,p)) method. For carbon-centered radical addition reactions, B3LYP/6-311G(d,p) slightly overestimates the length of the forming C-C bond as compared to the IRCMax data. A correlation to improve the agreement is proposed. For hydrogen addition reactions, MPW1K density functional theory (MPW1K/6-31G(d)) is able to locate transition states. However, the lengths of the forming C-H bonds are systematically longer than reference IRCMax data. Here, too, a correlation is proposed to improve the agreement. Transition state geometries for hydrogen abstraction reactions obtained with B3LYP/6-311G(d,p) show good agreement with the IRCMax reference data. Third, the improved transition state geometries are used to calculate activation energies at the CBS-QB3 level. Comparison between both CBS-QB3 and B3LYP density functional theory predictions shows deviations up to 25 kJ/mol. Although main trends are captured by B3LYP DFT, secondary trends due to radical nucleophilic effects are not reproduced accurately.},
  author       = {Saeys, Mark and Reyniers, Marie-Fran\c{c}oise and Marin, Guy and Van Speybroeck, Veronique and Waroquier, Michel},
  issn         = {1089-5639},
  journal      = {JOURNAL OF PHYSICAL CHEMISTRY A},
  keyword      = {DENSITY-FUNCTIONAL THEORY,HYDROGEN ABSTRACTION REACTION,SET MODEL CHEMISTRY,BOND-DISSOCIATION ENERGIES,REACTION-RATE PREDICTION,GROUP ADDITIVITY,RATE CONSTANTS,THEORETICAL PROCEDURES,SUBSTITUTED ALKENES,HARTREE-FOCK},
  language     = {eng},
  number       = {43},
  pages        = {9147--9159},
  title        = {Ab initio calculations for hydrocarbons : enthalpy of formation, transition state geometry, and activation energy for radical reactions},
  url          = {http://dx.doi.org/10.1021/jp021706d},
  volume       = {107},
  year         = {2003},
}

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