Gas phase reaction kinetics of complex organic molecules at temperatures of the interstellar medium: The OH + CH<sub>3</sub>OH case

Canosa, André

doi:10.1017/s1743921319006446

Cited by 6 publications

(9 citation statements)

References 32 publications

(29 reference statements)

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“…[96][97][98][99] There have been significant advances in low-temperature studies of reactions involving radicals and oxygenated volatile organic compounds or complex organic molecules. Systems that have received particular attention include reactions such as OH + CH 3 OH, OH + CH 3 CHO, OH + CH 3 C(O)CH 3 , and CH + H 2 CO. [100][101][102][103][104][105][106][107][108][109][110][111] While many of these CRESU studies have focused on the measurement of rate coefficients, in several cases interesting reaction dynamics were also observed. For example, several OH reaction pathways that involved tunnelling through the abstraction activation barrier were found to yield rate coefficients independent of pressure.…”

Section: Flow Tube Methodsmentioning

confidence: 99%

Low-temperature reaction dynamics of paramagnetic species in the gas phase

Miossec

Heazlewood

2022

Chem. Commun.

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Section: Flow Tube Methodsmentioning

confidence: 99%

Low-temperature reaction dynamics of paramagnetic species in the gas phase

Miossec

Heazlewood

2022

Chem. Commun.

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“…For instance, in the hydrogen abstraction reaction CH 3 OH + OH → [CH 3 OH···OH] → CH 2 OH + H 2 O depicted in Figure , the OH radical forms a pre-reactive complex by hydrogen bonding with the hydroxyl group of the methanol (CH 3 OH) before abstracting a methyl hydrogen via a tunneling mechanism to form products. − Because the transition state is chiral but the reactants are not, σ = 2 for this reaction. There is also a secondary reaction, which we do not consider here, in which the hydroxyl hydrogen is abstracted instead.…”

Section: Resultsmentioning

confidence: 99%

Microcanonical Tunneling Rates from Density-of-States Instanton Theory

Fang

Winter

Richardson

2020

J. Chem. Theory Comput.

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Semiclassical instanton theory is a form of quantum transition-state theory which can be applied to the computation of thermal reaction rates in complex molecular systems including quantum tunneling effects. There have been a number of attempts to extend the theory to treat microcanonical rates. However, the previous formulations are either computationally unfeasible for large systems due to an explicit sum over states or they involve extra approximations, which make them less reliable. We propose a robust and practical microcanonical formulation called density-of-states instanton theory, which avoids the sum over states altogether. In line with the semiclassical approximations inherent to the instanton approach, we employ the stationary-phase approximation to the inverse Laplace transform to obtain the densities of states. This can be evaluated using only post-processing of the data available from a small set of instanton calculations, such that our approach remains computationally efficient. We show that the new formulation predicts results that agree well with quantum scattering theory for an atom–diatom reaction and with experiments for a photoexcited unimolecular hydrogen transfer in a Criegee intermediate. When the thermal rate is evaluated from a Boltzmann average over our new microcanonical formalism, it can overcome some problems of conventional instanton theory. In particular, it predicts a smooth transition at the crossover temperature and is able to describe bimolecular reactions with pre-reactive complexes such as CH3OH + OH.

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“…Low temperature results on OH + CH 3 OH show the results to be independent of total density, hence binary, but there are theoretical (Gao et al, 2018) and experimental results to the contrary. For example, Ocaña et al (2019) showed the process to show some pressure dependence at 120-150 K, whereas no pressure dependence was found at temperatures below 100 K. A number of other theoretical treatments, including the quasiclassical trajectory approach and the ring polymer approach have been discussed by Canosa (2019). From the point of view of astrochemistry, if the OH + CH 3 OH reaction is indeed rapid and binary at 10 K, it is clearly important in the formation of CH 3 O (Acharyya et al, 2015;Balucani et al, 2015).…”

Section: Reactions With a U-shaped Rate Dependence On Temperaturementioning

confidence: 99%

Unusual Chemical Processes in Interstellar Chemistry: Past and Present

Herbst

2021

Front. Astron. Space Sci.

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The chemistry that occurs in interstellar clouds consists of both gas-phase processes and reactions on the surfaces of dust grains, the latter particularly on and in water-dominated ice mantles in cold clouds. Some of these processes, especially at low temperature, are very unusual by terrestrial standards. For example, in the gas-phase, two-body association reactions form a metastable species known as a complex, which is then stabilized by the emission of radiation under low-density conditions, especially at low temperatures. In the solid phase, it has been thought that the major process for surface reactions is diffusive in nature, occurring when two species undergoing random walks collide with each other on a surface that has both potential wells and intermediate barriers. There is experimental evidence for this process, although very few rates at low interstellar temperatures are well measured. Moreover, since dust particles are discrete, modeling has to take account that reactant pairs are on the same grain, a problem that can be treated using stochastic approaches. In addition, it has been shown more recently that surface reactions can occur more rapidly if they undergo any of a number of non-diffusive processes including so-called three-body mechanisms. There is some experimental support for this hypothesis. These and other unusual gaseous and solid-state processes will be discussed from the theoretical and experimental points of view, and their possible role in the synthesis of organic molecules in interstellar clouds explained. In addition, their historical development will be reviewed.

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Gas phase reaction kinetics of complex organic molecules at temperatures of the interstellar medium: The OH + CH₃OH case

Abstract: Recent experimental and theoretical works concerning gas-phase radical-neutral reactions involving Complex Organic Molecules are reviewed in the context of cold interstellar objects with a special emphasis on the OH + CH3OH reaction and its potential impact on the formation of CH3O.

Cited by 6 publications

References 32 publications

Low-temperature reaction dynamics of paramagnetic species in the gas phase

Low-temperature reaction dynamics of paramagnetic species in the gas phase

Microcanonical Tunneling Rates from Density-of-States Instanton Theory

Unusual Chemical Processes in Interstellar Chemistry: Past and Present

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Gas phase reaction kinetics of complex organic molecules at temperatures of the interstellar medium: The OH + CH3OH case

Abstract: Recent experimental and theoretical works concerning gas-phase radical-neutral reactions involving Complex Organic Molecules are reviewed in the context of cold interstellar objects with a special emphasis on the OH + CH3OH reaction and its potential impact on the formation of CH3O.

Cited by 6 publications

References 32 publications

Low-temperature reaction dynamics of paramagnetic species in the gas phase

Low-temperature reaction dynamics of paramagnetic species in the gas phase

Microcanonical Tunneling Rates from Density-of-States Instanton Theory

Unusual Chemical Processes in Interstellar Chemistry: Past and Present

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Product

Resources

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Gas phase reaction kinetics of complex organic molecules at temperatures of the interstellar medium: The OH + CH₃OH case