Dynamics of the CH<sub>3</sub> + OH reaction

Ree, Jongbaik; Kim, Y. H.; Shin, Hyung Kyu

doi:10.1002/kin.20568

Cited by 3 publications

(3 citation statements)

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“…However, that is beyond the scope of the current paper, which describes a new PES for CH 3 OH for both the bound region and dissociation to CH 3 + OH. It should be noted that a model, empirical PES has been reported for CH 3 + OH recombination and used in quasiclassical trajectory calculations [23]. The properties of the bound region of the PES were not reported and evidently were not included in the empirical determination of potential parameters in that work.…”

Section: Introductionmentioning

confidence: 97%

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Full-dimensional, ab initio potential energy surface for CH₃OH → CH₃+OH

Bowman

2013

Molecular Physics

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An accurate, ab initio potential energy surface (PES) is reported for CH 3 OH including the bound region as well as the barrierless dissociation to CH 3 + OH. The surface is a linear least-squares fit to a total of 45,199 ab initio energies, most of which were computed using CCSD(T)-F12b/aug-cc-pVDZ theory and a small number using CASPT2/aug-cc-pVDZ theory. The latter set was done in the multi-reference region of the PES in order to obtain a realistic description of the OH-CH 3 interaction in the near asymptotic region. The geometries and harmonic frequencies of the stationary points agree very well with direct CCSD(T)-F12b calculations. The three-fold barrier to internal rotation of CH 3 OH is also accurately described by the PES. The zero-point energies of methanol and CH 3 + OH are determined by Diffusion Monte Carlo calculations. The D 0 dissociation energy is 90.1 kcal/mol, in very good agreement with the recent IUPAC evaluation [Ruscic et al., J. Phys. Chem. Ref. Data 34, 573 (2005)] result of 90.25 kcal/mol. Keywords: potential energy surface; ab initio; methanol dissociation energy IntroductionThe rovibrational spectroscopy of methanol has been the subject of numerous experimental [1-8] and theoretical papers [9-17], with a focus on the facile internal torsional motion. Signatures of that motion in the vibrational spectrum of the fundamentals and overtones of the CH and OHstretch modes have been reported in recent experiments.Methanol is a challenging system for an ab initio approach, owing both to the dimensionality of the configuration space (12 vibrational degrees of freedom) and also the need to accurately describe the low-barrier torsional motion. High-level theoretical work on the vibration/torsion energies of CH 3 OH has made use of ab initio-based force fields and a potential that are limited to the region of the minimum of the potential [11][12][13][14][15][16][17]. The most recent of these [15] used electronic energies obtained using coupled-clustersingles-doubles and perturbative treatment of triples excitations (CCSD(T)) theory with large polarised basis sets, i.e. aug-cc-pVTZ. The limited PES we developed [15] was a fit to 19,315 CCSD(T)/aVTZ energies. That PES was used in MULTIMODE-Reaction Path calculations [15,16] of numerous low-lying vibration/torsion energies, which are in good agreement with experiment.That PES does not describe dissociation or near dissociation to any fragments, in particular to CH 3 + OH. These are among the dominant products of the thermal decomposition of CH 3 OH. That decomposition as well as the recombination of CH 3 + OH are important processes in combustion chemistry and have been studied over a range of

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Section: Introductionmentioning

confidence: 97%

“…Email: jmbowma@emory.edu temperatures and pressures for several decades. Recent work can be found in [18][19][20][21][22][23][24]. Methanol is also widely found in the interstellar medium and its mechanism of formation is still a subject of discussion [25].…”

Section: Introductionmentioning

confidence: 98%

Full-dimensional, ab initio potential energy surface for CH₃OH → CH₃+OH

Bowman

2013

Molecular Physics

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“…However, relative importance of the reaction channels is temperature and pressure dependent. 4 Fockenberg et al 5 reported that although at ambient temperature channels 1a and 1b are the major reaction channels, the relative contributions of channels 1a, 1b, 1e, and 1f at an elevated temperature (610 K) are comparable. 5 They used time-of-flight mass spectrometer connected to a tubular flow reactor.…”

Section: ■ Introductionmentioning

confidence: 99%

Reaction CH₃ + OH Studied over the 294–714 K Temperature and 1–100 bar Pressure Ranges

2012

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Reaction of methyl radicals with hydroxyl radicals, CH(3) + OH → products (1) was studied using pulsed laser photolysis coupled to transient UV-vis absorption spectroscopy over the 294-714 K temperature and 1-100 bar pressure ranges (bath gas He). Methyl radicals were produced by photolysis of acetone at 193.3 nm. Hydroxyl radicals were generated in reaction of electronically excited oxygen atoms O((1)D), produced in the photolysis of N(2)O at 193.3 nm, with H(2)O. Temporal profiles of CH(3) were recorded via absorption at 216.4 nm using xenon arc lamp and a spectrograph; OH radicals were monitored via transient absorption of light from a dc discharge H(2)O/Ar low pressure resonance lamp at ca. 308 nm. The absolute intensity of the photolysis light inside the reactor was determined by an accurate in situ actinometry based on the ozone formation in the presence of molecular oxygen. The results of this study indicate that the rate constant of reaction 1 is pressure independent within the studied pressure and temperature ranges and has slight negative temperature dependence, k(1) = (1.20 ± 0.20) × 10(-10)(T/300)(-0.49) cm(3) molecule(-1) s(-1).

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Reaction Dynamics of CH₃+ HBr → CH₄+ Br at 150-1000 K

Ree¹,

Kim²,

Shin³

2013

Bulletin of the Korean Chemical Society

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The kinetics of the radical-polar molecule reaction CH 3 + HBr → CH 4 + Br has been studied at temperatures between 150 and 1000 K using classical dynamics procedures. Potential energy surfaces constructed using analytical forms of inter-and intramolecular interaction energies show a shallow well and barrier in the entrance channel, which affect the collision dynamics at low temperatures. Different collision models are used to distinguish the reaction occurring at low-and high-temperature regions. The reaction proceeds rapidly via a complex-mode mechanism below room temperature showing strong negative temperature dependence, where the effects of molecular attraction, H-atom tunneling and recrossing of collision complexes are found to be important. The temperature dependence of the rate constant between 400 and 1000 K is positive, the values increasing in accordance with the increase of the mean speed of collision. The rate constant varies from 7.6 × 10 −12 at 150 K to 3.7 × 10 −12 at 1000 K via a minimum value of 2.5 × 10 −12 cm 3 molecule −1 s −1 at 400 K.

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Dynamics of the CH₃ + OH reaction

Cited by 3 publications

References 58 publications

Full-dimensional, ab initio potential energy surface for CH₃OH → CH₃+OH

Full-dimensional, ab initio potential energy surface for CH₃OH → CH₃+OH

Reaction CH₃ + OH Studied over the 294–714 K Temperature and 1–100 bar Pressure Ranges

Reaction Dynamics of CH₃+ HBr → CH₄+ Br at 150-1000 K

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Dynamics of the CH3 + OH reaction

Cited by 3 publications

References 58 publications

Full-dimensional, ab initio potential energy surface for CH3OH → CH3+OH

Full-dimensional, ab initio potential energy surface for CH3OH → CH3+OH

Reaction CH3 + OH Studied over the 294–714 K Temperature and 1–100 bar Pressure Ranges

Reaction Dynamics of CH3+ HBr → CH4+ Br at 150-1000 K

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Product

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About

Dynamics of the CH₃ + OH reaction

Full-dimensional, ab initio potential energy surface for CH₃OH → CH₃+OH

Full-dimensional, ab initio potential energy surface for CH₃OH → CH₃+OH

Reaction CH₃ + OH Studied over the 294–714 K Temperature and 1–100 bar Pressure Ranges

Reaction Dynamics of CH₃+ HBr → CH₄+ Br at 150-1000 K