Dynamics and quantum yields of H2 + CH2CO as a primary photolysis channel in CH3CHO

Harrison, Aaron W.; Kharazmi, Alireza; Shaw, Miranda F.; Quinn, Mitchell S.; Lee, Kelvin; Nauta, Klaas; Rowell, Keiran; Jordan, Meredith J. T.; Kable, Scott H.

doi:10.1039/c8cp06412a

Cited by 23 publications

(40 citation statements)

References 67 publications

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“…Harrison et al also revealed ketene as a major product in photolysis experiments conducted at 305.6 nm and confirmed that this molecule forms alongside molecular hydrogen from acetaldehyde molecules. [57] In the solid phase, only limited studies were conducted. [58] On the other hand, electron spin resonance (ESR) studies of solid acetaldehyde in noble gas matrices at 77 K exposed to high energy electrons (1 MeV) revealed acetyl (CH3ĊO) to be the dominating radical.…”

Section: Introductionmentioning

confidence: 99%

On the Formation of the Popcorn Flavorant 2,3‐Butanedione (CH₃COCOCH₃) in Acetaldehyde‐Containing Interstellar Ices

et al. 2020

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Section: Introductionmentioning

confidence: 99%

On the Formation of the Popcorn Flavorant 2,3‐Butanedione (CH₃COCOCH₃) in Acetaldehyde‐Containing Interstellar Ices

et al. 2020

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“…There has been recent interest in the formation of ketenes as atypical and relatively uncharacterised products of carbonyl photolysis (Harrison et al, 2019;Toulson et al, 2018). As seen above, the formyl + α H 2 -loss mechanism forms ketenes in aldehydes and the AE mechanism forms ketenes in ketones.…”

Section: Enal-ketene Tautomerisationmentioning

confidence: 99%

“…7 reinforce, for multiple carbonyl species, that only H 2 -loss from the formyl and α positions is energetically accessible in the actinic energy range. Indeed, the 4-centre H 2 -loss channel in acetaldehyde has recently been observed experimentally under tropospherically relevant conditions (Harrison et al, 2019). In the absence of a formyl hydrogen, none of the ketone H 2 -loss channels are accessible in the troposphere.…”

mentioning

confidence: 98%

Photo-initiated ground state chemistry: How important is it in the atmosphere?

Rowell

Kable

Jordan

2021

Preprint

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Abstract. Carbonyls are among the most abundant volatile organic compounds in the atmosphere. They are central to atmospheric photochemistry as absorption of near-UV radiation by the C=O chromophore can lead to photolysis. If photolysis does not occur on electronic excited states, non-radiative relaxation to the ground state will form carbonyls with extremely high internal energy. These “hot” molecules can access a range of ground state reactions. Up to nine potential ground state reactions are investigated at the B2GP-PLYP-D3/def2-TZVP level of theory for a dataset of 20 representative carbonyls. Almost all are energetically accessible under tropospheric conditions. Comparison with experiment suggests the most significant ground state dissociation pathways will be concerted triple fragmentation in saturated aldehydes, Norrish type III dissociation to form another carbonyl, and H2-loss involving the formyl H atom in aldehydes. Tautomerisation, leading to more reactive unsaturated species, is also predicted to be energetically accessible and is likely to be important when there is no low-energy ground state dissociation pathway, for example in α,β-unsaturated carbonyls and some ketones. The concerted triple fragmentation and H2-loss pathways have immediate atmospheric implication to global H2 production and tautomerisaton has implication to the atmospheric production of organic acids.

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“…The most apparent difference in the photochemistry of these molecules is in the minor pathway producing CH 2 CO + H 2 in CH 3 CHO [20]. The transition state for the analogous pathway in CF 3 CHO could not be located; instead a hydrogen-bonding interaction is formed between the formyl H-atom and a fluoromethyl fluorine atom leading to CF 2 , HF and CO products.…”

Section: Photodissociation Pathwaysmentioning

confidence: 99%

Photodissociation of CF3CHO provides a new source of CHF3 (HFC-23) in the atmosphere: implications for new refrigerants.

Hansen

Campbell

Kable

2021

Preprint

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Throughout the last century, chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) were the most widely used refrigerants. However, it was discovered that they released reactive chlorine in the upper atmosphere causing the hole in the ozone layer and they were phased out by the 1987 Montreal Protocol [1]. They were replaced by hydrofluorocarbons (HFCs), which contain no chlorine and do not damage the ozone layer. However, HFCs are potent greenhouse gases and they were phased out in a 2016 amendment to the Montreal Protocol [2]. The latest evolution of these refrigerants is the hydrofluoroolefins (HFOs). These molecules have no chlorine and incorporate a carbon-carbon double bond to greatly reduce their atmospheric lifetime, and hence their contribution as a greenhouse gas. In this work, we demonstrate that one of the most important HFOs in current use ultimately decomposes partially into HFC-23 (CHF3) in the atmosphere. HFC-23 is one of the most potent greenhouse gases known, and the most potent HFC. Despite its phaseout, the observed emissions of HFC-23 have been increasing recently and were the largest in history in 2018 with no conclusive explanation [3]. This work suggests that the production of HFOs might be partially responsible.

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Dynamics and quantum yields of H₂ + CH₂CO as a primary photolysis channel in CH₃CHO

Abstract: A new ketene + H2 channel in CH3CHO photolysis is not modelled by quasi-classical trajectories over the transition state.

Cited by 23 publications

References 67 publications

On the Formation of the Popcorn Flavorant 2,3‐Butanedione (CH₃COCOCH₃) in Acetaldehyde‐Containing Interstellar Ices

On the Formation of the Popcorn Flavorant 2,3‐Butanedione (CH₃COCOCH₃) in Acetaldehyde‐Containing Interstellar Ices

Photo-initiated ground state chemistry: How important is it in the atmosphere?

Photodissociation of CF3CHO provides a new source of CHF3 (HFC-23) in the atmosphere: implications for new refrigerants.

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Dynamics and quantum yields of H2 + CH2CO as a primary photolysis channel in CH3CHO

Abstract: A new ketene + H2 channel in CH3CHO photolysis is not modelled by quasi-classical trajectories over the transition state.

Cited by 23 publications

References 67 publications

On the Formation of the Popcorn Flavorant 2,3‐Butanedione (CH3COCOCH3) in Acetaldehyde‐Containing Interstellar Ices

On the Formation of the Popcorn Flavorant 2,3‐Butanedione (CH3COCOCH3) in Acetaldehyde‐Containing Interstellar Ices

Photo-initiated ground state chemistry: How important is it in the atmosphere?

Photodissociation of CF3CHO provides a new source of CHF3 (HFC-23) in the atmosphere: implications for new refrigerants.

Contact Info

Product

Resources

About

Dynamics and quantum yields of H₂ + CH₂CO as a primary photolysis channel in CH₃CHO

On the Formation of the Popcorn Flavorant 2,3‐Butanedione (CH₃COCOCH₃) in Acetaldehyde‐Containing Interstellar Ices

On the Formation of the Popcorn Flavorant 2,3‐Butanedione (CH₃COCOCH₃) in Acetaldehyde‐Containing Interstellar Ices