Variational Transition State Theory

Truhlar, Donald G.; Garrett, Bruce C.

doi:10.1146/annurev.pc.35.100184.001111

Cited by 888 publications

(620 citation statements)

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“…The required potential energy surface (PES) information for the kinetic calculations was obtained directly from the electronic structure calculations, in which the M06-2X density functional method 16 was used to optimize all the stationary points on the PES, and multilevel MCG3-MPWB method 17 was used to calculate the highlevel single-point energies at the M06-2X geometries. The rate constants were evaluated using variational transition state theory (VTST) [18][19][20] with interpolated single-ponit energies (ISPE) 21 approach. The comparison between theoretical and experimental results is made.…”

Section: Introductionmentioning

confidence: 99%

Theoretical Studies on Mechanism and Kinetics of the Hydrogen-Abstraction Reaction of CF₃CH₂CHO with OH Radicals

Ci¹,

Yu²,

Wan³

et al. 2011

Bulletin of the Korean Chemical Society

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The hydrogen abstraction reaction of CF 3 CH 2 CHO + OH has been studied theoretically by dual-level direct dynamics method. Two stable conformers, trans-and cis-CF 3 CH 2 CHO, have been located, and there are four distinct OH hydrogen-abstraction channels from t-CF 3 CH 2 CHO and two channels from c-CF 3 CH 2 CHO. The required potential energy surface information for the kinetic calculation was obtained at the MCG3-MPWB// M06-2X/aug-cc-pVDZ level. The rate constants, which were calculated using improved canonical transitionstate theory with small-curvature tunneling correction (ICVT/SCT) were fitted by a four-parameter Arrhenius equation. It is shown that the reaction proceeds predominantly via the H-abstraction from the -CHO group over the temperature range 200-2000 K. The calculated rate constants were in good agreement with the experimental data between 263 and 358 K.

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Section: Introductionmentioning

confidence: 99%

Theoretical Studies on Mechanism and Kinetics of the Hydrogen-Abstraction Reaction of CF₃CH₂CHO with OH Radicals

Ci¹,

Yu²,

Wan³

et al. 2011

Bulletin of the Korean Chemical Society

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“…Canonical variational transition state theory (CVT) 6 was used to locate the transition structure (TS) for the ring opening of 1 to 2. Quantum effects on the reaction dynamics were computed semiclassically, using the small-curvature tunneling (SCT) approximation.…”

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confidence: 99%

Calculations Predict a Large Inverse H/D Kinetic Isotope Effect on the Rate of Tunneling in the Ring Opening of Cyclopropylcarbinyl Radical

et al. 2009

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Tunneling rates are expected to decrease exponentially with the square root of the effective tunneling mass. 1a Therefore, on substitution of a heavier for a lighter isotope, the observation of a large kinetic isotope effect (KIE), involving a substantial decrease in rate constant, is a commonly used diagnostic for a large contribution from quantum mechanical tunneling to a reaction. 1 However, in this communication we report the results of calculations that make the opposite prediction about some of the KIEs on the ring opening of cyclopropylcarbinyl radical (1) to 3-butene-1-yl radical (2) 2 by tunneling at cryogenic temperatures. 3 Substitution of a heavier for a lighter isotope at the radical center (C 1 ) of 1 is calculated to accelerate the rate of tunneling, giving KIEs at this carbon that are inverse. Of particular note is our prediction that substitution of deuterium for both hydrogens at C 1 will lead to a nearly 3-fold increase in the rate of reaction at temperatures so low that ring opening proceeds exclusively by tunneling from the lowest vibrational level.As in our previous computational study of tunneling in the ring opening of 1 to 2, 3 we performed unrestricted electronic structure calculations with B3LYP 4 and the 6-31G(d) basis set, 5 to carry out direct dynamics calculations of the rate of this reaction. Canonical variational transition state theory (CVT) 6 was used to locate the transition structure (TS) for the ring opening of 1 to 2. Quantum effects on the reaction dynamics were computed semiclassically, using the small-curvature tunneling (SCT) approximation. 7 The direct dynamics calculations were carried out with GAUSSRATE 8 as the interface between Gaussian 03 9 and POLYRATE. 10

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“…We fit the reaction rate constants in the temperature range of 300 -1500 K at the high-pressure limit. Estimating reaction rate constants for barrierless fission of the C-OOH and O-OH bonds necessitates treatment by the variational transition state theory (VTST) [45]. However, CBS-QB3 composite method could not establish the reliable minimum energy point (MEP) curve along the assigned stretching of the C-OOH/O-OH bonds.…”

Section: Potential Energy Surfaces (Pess)mentioning

confidence: 99%

Reactions of HO2 with n-propylbenzene and its phenylpropyl radicals

Altarawneh

Dlugogorski

2015

Combustion and Flame

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Abstraction of an H atom from the propyl side chain by hydroperoxyl radicals (HO 2 ) constitutes a central reaction in the low-temperature oxidation of n-propylbenzene (nPB).Herein, we calculate reaction rate constants for H abstraction from primary, secondary and benzylic sites in nPB. Rate of abstraction of a benzylic H atom dominates that of a secondary H atom with negligible abstraction of the primary H atom at T ≥ 600 K. We present the reaction enthalpies for 1-phenyl-1-propyl (R1), 1-phenyl-2-propyl (R2) and 1-phenyl-3-propyl (R3) radicals, and compare the computed reaction rate constants and bond dissociation enthalpies with analogous scarce literature values. Addition of HO 2 radicals to radical sites in R1, R2 and R3 proceeds in a highly exothermic process and results in the formation of HO 2 -phenylpropyl adducts. Mapped potential energy surfaces illustrate all plausible exit channels of the three HO 2 -phenylpropyl adducts. Master equation calculations for the three phenylpropyl + HO 2 reactions indicate that direct O-OH bond fission and water elimination control the fate of the adducts leading to the formation of ketonic-type structures. Results from this study should be useful to update kinetic models for the low-temperature oxidation of alkylbenzenes in general.

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Variational Transition State Theory

Cited by 888 publications

References 0 publications

Theoretical Studies on Mechanism and Kinetics of the Hydrogen-Abstraction Reaction of CF₃CH₂CHO with OH Radicals

Theoretical Studies on Mechanism and Kinetics of the Hydrogen-Abstraction Reaction of CF₃CH₂CHO with OH Radicals

Calculations Predict a Large Inverse H/D Kinetic Isotope Effect on the Rate of Tunneling in the Ring Opening of Cyclopropylcarbinyl Radical

Reactions of HO2 with n-propylbenzene and its phenylpropyl radicals

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Variational Transition State Theory

Cited by 888 publications

References 0 publications

Theoretical Studies on Mechanism and Kinetics of the Hydrogen-Abstraction Reaction of CF3CH2CHO with OH Radicals

Theoretical Studies on Mechanism and Kinetics of the Hydrogen-Abstraction Reaction of CF3CH2CHO with OH Radicals

Calculations Predict a Large Inverse H/D Kinetic Isotope Effect on the Rate of Tunneling in the Ring Opening of Cyclopropylcarbinyl Radical

Reactions of HO2 with n-propylbenzene and its phenylpropyl radicals

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Theoretical Studies on Mechanism and Kinetics of the Hydrogen-Abstraction Reaction of CF₃CH₂CHO with OH Radicals

Theoretical Studies on Mechanism and Kinetics of the Hydrogen-Abstraction Reaction of CF₃CH₂CHO with OH Radicals