Elucidation of structure–reactivity relationships in hindered phenols via quantum chemistry and transition state theory

Pfaendtner, Jim; Broadbelt, Linda J.

doi:10.1016/j.ces.2006.12.080

Cited by 23 publications

(21 citation statements)

References 47 publications

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“…The corresponding rate constant using Eckart tunneling correction is 8.48 × 10 9 M −1 s −1 , which is 30.5% higher than the experimental value. It is reported that the Eckart method is often found to overestimate the tunneling corrections . The calculated rate constant using Wigner's method is in a good agreement with the experimental value.…”

Section: Resultssupporting

confidence: 61%

Thermodynamic and kinetic study of ibuprofen with hydroxyl radical: A density functional theory approach

Xiao

Noerpel

Luk

et al. 2013

Int. J. Quantum Chem.

103

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Ibuprofen, a frequently detected pharmaceutical in natural and engineered waters, was studied in both neutral and anionic forms using density functional theory at the B3LYP/6-31111G**//B3LYP/6-31G* level of theory in its reaction with hydroxyl radical ( • OH). The reaction pathways included • OH addition to aromatic ring, abstraction of a H-atom, and nucleophilic attack on the carbonyl group. The results showed that H-atom abstraction pathways are the most favorable. The free energy change for H-atom abstraction reaction ranges from 237.8 to 215.9 kcal/mol; for • OH addition ranges from 23.85 to 21.23 kcal/mol; and for nucleophilic attack on the carbonyl group is 13.9 kcal/mol. The calculated rate constant between neutral ibuprofen and • OH, 6.72 3 10 9 M 21 s 21 , is consistent with the experimental value, 6.5 6 0.2 3 10 9 M 21 s 21 . Our results provide direct evidence for byproduct formation and identification on the molecular level.

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Section: Resultssupporting

confidence: 61%

Thermodynamic and kinetic study of ibuprofen with hydroxyl radical: A density functional theory approach

Xiao

Noerpel

Luk

et al. 2013

Int. J. Quantum Chem.

103

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“…22 ■ RESULTS AND DISCUSSION Bonded States. Similarly to the results of Pfaendtner and Broadbelt on hindered phenols, 19 we find that the combined reactants/products optimized from the IRC calculation were lower in zero-point-corrected electronic energy than the sum of the separated reactants/products. For instance, the combined reactants had a zero-point-corrected electronic energy of 3.02 kcal/mol lower compared to the sum of each individual reactant molecule.…”

Section: ■ Computational Detailssupporting

confidence: 86%

Section: ■ Computational Detailsmentioning

confidence: 99%

“…To do so, the total partition functions of the reactants and the transition state were computed using the optimized geometries under the rigid rotor harmonic (HO) approximation and a Hessian calculation. While this approximation treats the low-frequency torsional modes incorrectly, it was shown by Pfaendtner et al in a similar study on hindered phenols that correctly treating these internal rotations has only a minor effect on the activation energy and the vibrational contribution to the internal energy. The temperature-dependent rate constant is given by the usual expression in the high-pressure limit: where n is the molecularity of the reaction, c 0 is the standard state concentration to which the translational partition function is referenced ( P / RT ), Q sad and Q ini are the total partition functions for the saddle and initial configurations, respectively, E o is the zero-point-corrected reaction barrier, and κ( T ) is the correction for quantum tunneling.…”

Section: Computational Detailsmentioning

confidence: 99%

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Density Functional Theory Rate Calculation of Hydrogen Abstraction Reactions of N-Phenyl-α-naphthylamine Antioxidants

Joly

Miller

2017

Ind. Eng. Chem. Res.

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Quantum chemistry and transition state theory were used to investigate the hydrogen abstraction reaction of N-phenyl-α-naphthylamine with a series of alkylperoxy radicals. We correctly identify the transition state both in vacuum and under solvation before extracting a reaction rate constant using harmonic transition state theory. As expected, more polar solvents strongly reduce the rate constants. Our results compare favorably with the known experimental data and extend the database of reaction constants that can be used to simulate chemical kinetics for lubricant systems.

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“…It is certainly not reasonable to assume that this result holds for other classes of H-migration reactions, as the Eckart model sometimes overestimates the tunneling correction for some reactions. [67][68][69] In combustion, peroxy radical chemistry often occurs in the fall-off region rather than at the high pressure limit, and tunneling can be enormously more important in the fall-off region 28,29 because the high-energy tail of the Boltzmann distribution is depleted. It is therefore of interest to compare energy-dependent transmission coefficients, G(E), computed by various methods, as shown in Fig.…”

Section: Tunnelingmentioning

confidence: 99%

Impact of tunneling on hydrogen-migration of the n-propylperoxy radical

Zhang

Dibble

2011

Phys. Chem. Chem. Phys.

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The kinetics of three unimolecular reactions of the n-propylperoxy radical were studied by canonical variational transition state theory and multidimensional small curvature tunneling (SCT). The reactions studied were 1,5 and 1,4 H-migration, and HO(2) elimination. Benchmark calculations were carried out at the CCSD(T) level in order to determine which density functional to use for SCT calculations for each reaction. For 1,5 and 1,4 H-migration, and HO(2) elimination, the M05-2X, B3LYP and B1B95 functionals, respectively, performed closest to the benchmark when coupled to the 6-311+G(2df,2p) basis set. The SCT tunneling corrections, κ(T), computed here were much larger than those calculated from the Wigner or zero-curvature tunneling treatments at low temperatures, but the asymmetric Eckart method works surprisingly well in these three reactions. Comparison of energy-dependent transmission coefficients, Γ(E), indicates that not only the magnitude, but also the sign, of the error in the Eckart approximation is a function of energy; therefore, the error introduced by using the Eckart approach depends strongly on the steady state energy distribution. These results may provide guidance for future studies of tunneling effects in reactions of other peroxy radicals.

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Elucidation of structure–reactivity relationships in hindered phenols via quantum chemistry and transition state theory

Cited by 23 publications

References 47 publications

Thermodynamic and kinetic study of ibuprofen with hydroxyl radical: A density functional theory approach

Thermodynamic and kinetic study of ibuprofen with hydroxyl radical: A density functional theory approach

Density Functional Theory Rate Calculation of Hydrogen Abstraction Reactions of N-Phenyl-α-naphthylamine Antioxidants

Impact of tunneling on hydrogen-migration of the n-propylperoxy radical

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