Pressure and temperature dependent photolysis of glyoxal in the 355–414 nm region: evidence for dissociation from multiple states

Salter, Robert J.; Blitz, Mark A.; Heard, Dwayne E.; Pilling, Michael J.; Seakins, Paul W.

doi:10.1039/c3cp43596b

Cited by 12 publications

(22 citation statements)

References 32 publications

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“…This is the first report of a clear effect of pressure on the photolysis quantum yield of gas-phase pyruvic acid. Nevertheless, there are studies of other carbonyl molecules, including acetaldehyde and acetone, that exhibit a similar decrease in quantum yield with increasing buffer gas pressures. − ,, …”

Section: Discussionmentioning

confidence: 99%

“…We conducted a Stern–Volmer analysis to explore the possibility of collisional deactivation as the mechanism for the decrease in quantum yield. If only the singlet state is actively quenched, we expect a linear relationship between 1/ϕ and [M]; however, if both the singlet and triplet states are accessible and quenched, a Stern–Volmer analysis will result in a nonlinear curve. ,, According to the known primary pathway for decarboxylation (Scheme ), the mechanism begins by exciting pyruvic acid (PA) to a reactive singlet state (PA(S)*, eq ), which could be in either S 1 or S 0 . PA(S)* then decarboxylates to form CO 2 and methylhydroxycarbene (eq ).…”

Section: Discussionmentioning

confidence: 99%

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Gas-Phase Photolysis of Pyruvic Acid: The Effect of Pressure on Reaction Rates and Products

et al. 2016

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In this work, we investigate the impact of pressure and oxygen on the kinetics of and products from the gas-phase photolysis of pyruvic acid. The results reveal a decrease in the photolysis quantum yield as pressure of air or nitrogen is increased, a trend not yet documented in the literature. A Stern-Volmer analysis demonstrates this effect is due to deactivation of the singlet state of pyruvic acid when the photolysis is performed in nitrogen, and from quenching of both the singlet and triplet state in air. Consistent with previous studies, acetaldehyde and CO are observed as the major products; however, other products, most notably acetic acid, are also identified in this work. The yield of acetic acid increases with increasing pressure of buffer gas, an effect that is amplified by the presence of oxygen. At least two mechanisms are necessary to explain the acetic acid, including one that requires reaction of photolysis intermediates with O. These findings extend the fundamental understanding of the gas-phase photochemistry of pyruvic acid, highlighting the importance of pressure on the photolysis quantum yields and products.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Gas-Phase Photolysis of Pyruvic Acid: The Effect of Pressure on Reaction Rates and Products

et al. 2016

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“…The S 0 asymptotic ener-gies for NTIa are slightly lower than the triplet thresholds, giving an energetic window for S 0 radical dissociation. Indeed, in glyoxal, two distinct, wavelength-dependent mechanisms of HCO q formation have been observed and attributed to dissociation on two electronic states (Chen and Zhu, 2003;Kao et al, 2004;Salter et al, 2013). Decarbonylation to form H 2 CO + CO and TF to form H 2 + 2 CO have the lowest energy thresholds in glyoxal, at 225 and 247 kJ/mol, respectively.…”

Section: Other Carbonylsmentioning

confidence: 99%

An assessment of the tropospherically accessible photo-initiated ground state chemistry of organic carbonyls

2022

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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 test set 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 implications for global H2 production, and tautomerisation has implications for the atmospheric production of organic acids.

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“…The S 0 asymptotic energies for NTIa are slightly lower than the triplet thresholds, giving an energetic window for S 0 radical dissociation. Indeed, in glyoxal, two distinct, wavelength-dependent mechanisms of HCO • formation have been observed and attributed to dissociation on two electronic states (Chen and Zhu, 2003;Kao et al, 2004;Salter et al, 2013). Decarbonylation to form H 2 CO + CO and TF to form H 2 + 2CO have the lowest energy thresholds in glyoxal, at 225 and 247 kJ/mol, respectively.…”

Section: Other Carbonylsmentioning

confidence: 99%

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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Pressure and temperature dependent photolysis of glyoxal in the 355–414 nm region: evidence for dissociation from multiple states

Cited by 12 publications

References 32 publications

Gas-Phase Photolysis of Pyruvic Acid: The Effect of Pressure on Reaction Rates and Products

Gas-Phase Photolysis of Pyruvic Acid: The Effect of Pressure on Reaction Rates and Products

An assessment of the tropospherically accessible photo-initiated ground state chemistry of organic carbonyls

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

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