Thermal Rate Constants for the O(3P) + CH4→ OH + CH3Reaction: The Effects of Quantum Tunneling and Potential Energy Barrier Shape

Zhao, Hongbo; Zhao, Yi

doi:10.1021/acs.jpca.6b07029

Cited by 15 publications

(18 citation statements)

References 72 publications

(129 reference statements)

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“…Kinetic isotope effects (KIEs) can be used to elucidate mechanisms and, because they are especially sensitive to tunneling and zero-point energy (ZPE), they provide quantitative tests of the reliability of simulations. − Inclusion of quantal effects in simulations of complex processes such as enzyme catalysis, proton-coupled electron transfer, and hydrogen-atom transfer in atmospheric reactions is critical for calculating accurate rate constants and KIEs. ,,,− Here, we demonstrate the importance of reaction-coordinate-dependent anharmonicity for calculating KIEs.…”

mentioning

confidence: 86%

Large Anharmonic Effects on Tunneling and Kinetics: Reaction of Propane with Muonium

Gao

Fleming

Truhlar

et al. 2021

J. Phys. Chem. Lett.

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Calculations of kinetic isotope effects (KIEs) provide challenging tests of quantal mass effects on reaction rates, and muonium KIEs are the most challenging. Here, we show that it can be very important to include reaction-coordinate-dependent vibrational anharmonicity along the whole reaction path to calculate tunneling probabilities and KIEs. For the reaction of propane with Mu, this decreases both the height and width of the vibrationally adiabatic potential barrier, with both effects increasing the rate constants. Our results agree well with the experimental observations.

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mentioning

confidence: 86%

Large Anharmonic Effects on Tunneling and Kinetics: Reaction of Propane with Muonium

Gao

Fleming

Truhlar

et al. 2021

J. Phys. Chem. Lett.

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“…Walch & Dunning Jr. 1980;Zhao et al 2016). Such an abstraction channel could conceivably lead to CH 3 OH production through radical recombination, however this is unlikely due to the high theoretical energy barrier.…”

Section: Reaction Networkmentioning

confidence: 99%

“…In contrast, ground state O( 3 P) oxygen atoms follow an abstraction channel with CH 4 to produce OH + CH 3 , with an estimated barrier of over 5000K (e.g. Walch & Dunning Jr. 1980;Zhao et al 2016). Such an abstraction channel could conceivably lead to CH 3 OH production through radical recombination, however this is unlikely due to the high theoretical energy barrier.…”

Section: Reaction Networkmentioning

confidence: 99%

Methanol Formation via Oxygen Insertion Chemistry in Ices

Bergner

Öberg

Rajappan

2017

ApJ

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We present experimental constraints on the insertion of oxygen atoms into methane to form methanol in astrophysical ice analogs. In gas-phase and theoretical studies this process has previously been demonstrated to have a very low or non-existent energy barrier, but the energetics and mechanisms have not yet been characterized in the solid state. We use a deuterium UV lamp filtered by a sapphire window to selectively dissociate O 2 within a mixture of O 2 :CH 4 and observe efficient production of CH 3 OH via O( 1 D) insertion. CH 3 OH growth curves are fit with a kinetic model, and we observe no temperature dependence of the reaction rate constant at temperatures below the oxygen desorption temperature of 25K. Through an analysis of side products we determine the branching ratio of icephase oxygen insertion into CH 4 : ∼65% of insertions lead to CH 3 OH with the remainder leading instead to H 2 CO formation. There is no evidence for CH 3 or OH radical formation, indicating that the fragmentation is not an important channel and that insertions typically lead to increased chemical complexity. CH 3 OH formation from O 2 and CH 4 diluted in a CO-dominated ice similarly shows no temperature dependence, consistent with expectations that insertion proceeds with a small or nonexistent barrier. Oxygen insertion chemistry in ices should therefore be efficient under low-temperature ISM-like conditions, and could provide an important channel to complex organic molecule formation on grain surfaces in cold interstellar regions such as cloud cores and protoplanetary disk midplanes.

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“…In this work, we focused on two goals: one was to reveal how the surface coverage affected H penetration and resurface rate constants on Ni(111) and the other was to explore the reaction mechanism of H 2 recombination by a subsurface H and a surface H. The rate constants were determined with the quantum instanton (QI) method. − This method could deal with complex systems with large degrees of freedom and it incorporated the quantum tunneling effect by taking into account all possible tunnel paths. It had successfully predicted the rate constants and kinetic isotope effects for gas-phase and gas-surface reactions. − …”

Section: Introductionmentioning

confidence: 99%

H Resurface and Hot H Promoted H₂ Recombination on Ni(111): Effects of Arrangement, Surface Coverage, and Lattice Motion

Ying

2021

J. Phys. Chem. C

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Subsurface H can affect catalytic reactivity and selectivity. H resurface and H2 recombination with a subsurface H on Ni(111) were investigated by the quantum instanton method, and the arrangement, surface coverage, lattice motion, and hot H effects were explored. The arrangement effect of a surface H and a subsurface H varied the H resurfacing rate constant by 57 times at 300 K. From the clean Ni(111) to two H adsorbed Ni(111), the increase of surface coverage suppressed the H resurfacing rate constant by four orders of magnitude at 300 K, whereas it increased the H penetration rate constant by about 10 times. The lattice motion effect was extremely remarkable for H resurface, H penetration, and direct H2 recombination, which enhanced the corresponding rate constants by about 10, 14, and 9 orders of magnitude, respectively, at 300 K. The hot resurfacing H could speed up H2 recombination by 140 times at 300 K. For the H2 recombination of a surface H and a subsurface H, the two-step process was much faster than the direct process. In the two-step process, H resurface was the rate-limiting step at extremely low temperatures due to the frozen lattice, while the recombination of two surface H atoms became the rate-limiting step as the lattice was relaxed with increasing temperature.

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Thermal Rate Constants for the O(³P) + CH₄→ OH + CH₃Reaction: The Effects of Quantum Tunneling and Potential Energy Barrier Shape

Cited by 15 publications

References 72 publications

Large Anharmonic Effects on Tunneling and Kinetics: Reaction of Propane with Muonium

Large Anharmonic Effects on Tunneling and Kinetics: Reaction of Propane with Muonium

Methanol Formation via Oxygen Insertion Chemistry in Ices

H Resurface and Hot H Promoted H₂ Recombination on Ni(111): Effects of Arrangement, Surface Coverage, and Lattice Motion

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Thermal Rate Constants for the O(3P) + CH4→ OH + CH3Reaction: The Effects of Quantum Tunneling and Potential Energy Barrier Shape

Cited by 15 publications

References 72 publications

Large Anharmonic Effects on Tunneling and Kinetics: Reaction of Propane with Muonium

Large Anharmonic Effects on Tunneling and Kinetics: Reaction of Propane with Muonium

Methanol Formation via Oxygen Insertion Chemistry in Ices

H Resurface and Hot H Promoted H2 Recombination on Ni(111): Effects of Arrangement, Surface Coverage, and Lattice Motion

Contact Info

Product

Resources

About

Thermal Rate Constants for the O(³P) + CH₄→ OH + CH₃Reaction: The Effects of Quantum Tunneling and Potential Energy Barrier Shape

H Resurface and Hot H Promoted H₂ Recombination on Ni(111): Effects of Arrangement, Surface Coverage, and Lattice Motion