Isomerization as a Primary Process in the Photolysis of Crotonaldehyde

McDowell, C. A.; Sifniades, Stylianos

doi:10.1021/ja00882a057

Cited by 25 publications

(14 citation statements)

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“…Quantification of BM and CA was done by comparison of the peak height to standard curves (r > 0.99) obtained with reference materials. Quantification of 3-butenal was done by comparison of the 3-butenal peak height to that of the CA standard since commercial 3-butenal was not available and attempts to obtain a pure sample of 3-butenal by synthesis (23,24) were hampered by its rapid tautomerization to CA. The effect of pH on 3-butenal conversion to CA was studied by incubating 0.25 mL of a 2.0 units/mL solution of chloroperoxidase with 0.25 mL of 2 mM H2O2 at 25 °C at pH 6.0 for 10 min to form 3-butenal.…”

Section: Methodsmentioning

confidence: 99%

Chloroperoxidase-mediated oxidation of 1,3-butadiene to 3-butenal, a crotonaldehyde precursor

Duescher

Elfarra²

1993

Chem. Res. Toxicol.

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Previously, we have shown that 1,3-butadiene, a rodent and possibly a human carcinogen, can be oxidized by chloroperoxidase-H2O2 at pH 7.4 to yield the potent mutagens, butadiene monoxide and crotonaldehyde. Because the crotonaldehyde/butadiene monoxide ratio from reactions with chloroperoxidase was higher than that obtained from reactions with myeloperoxidase or cytochrome P450 enzymes, in the present study, the chloroperoxidase reaction was further investigated in an attempt to define optimal conditions for catalysis and to possibly obtain direct evidence for the formation of the crotonaldehyde precursor 3-butenal in these incubations. The results showed that butadiene monoxide and crotonaldehyde formation was optimal at pH 6.0. As opposed to incubations carried out at pH 7.4, GC analyses of incubations carried out at pH 4.5, 5.0, and 6.0 demonstrated the presence of a new peak which had a retention time different from that of butadiene monoxide and crotonaldehyde. The new peak was identified as 3-butenal by comparison of its retention time and mass spectrum with those of reference material. Evidence for 3-butenal being a precursor of crotonaldehyde was obtained by the findings that 3-butenal was not simply a decomposition product of butadiene monoxide or crotonaldehyde under the incubation or assay conditions, and that the 3-butenal/crotonaldehyde ratio decreased when the incubation time was increased between 5 and 30 min or when the incubation temperature was increased between 10 and 45 degrees C. The combined 3-butenal and crotonaldehyde concentrations remained constant at the various incubation temperatures. Furthermore, 3-butenal conversion to crotonaldehyde was faster at pH 7.4, compared to pH 6.0.(ABSTRACT TRUNCATED AT 250 WORDS)

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Section: Methodsmentioning

confidence: 99%

Chloroperoxidase-mediated oxidation of 1,3-butadiene to 3-butenal, a crotonaldehyde precursor

Duescher

Elfarra²

1993

Chem. Res. Toxicol.

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“…30 Isomerization to but-3-enal has also been suggested as a pathway for E-crotonaldehyde photolysis. 31 Regardless, it appears that Norrish type I and II processes, which are the dominant reaction pathways for the photolysis of saturated aldehydes, are not important for conjugated aldehyde systems.…”

Section: Mechanistic Pathwaysmentioning

confidence: 99%

The atmospheric photolysis of E-2-hexenal, Z-3-hexenal and E,E-2,4-hexadienal

O’Connor

Wenger

Mellouki

et al. 2006

Phys. Chem. Chem. Phys.

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The atmospheric photolysis of E-2-hexenal, Z-3-hexenal and E,E-2,4-hexadienal has been investigated at the large outdoor European Photoreactor (EUPHORE) in Valencia, Spain. E-2-Hexenal and E,E-2,4-hexadienal were found to undergo rapid isomerization to produce Z-2-hexenal and a ketene-type compound (probably E-hexa-1,3-dien-1-one), respectively. Both isomerization processes were reversible with formation of the reactant slightly favoured. Values of j(E-2-hexenal)/j(NO(2)) = (1.80 +/- 0.18) x 10(-2) and j(E,E-2,4-hexadienal)/j(NO(2)) = (2.60 +/- 0.26) x 10(-2) were determined. The gas phase UV absorption cross-sections of E-2-hexenal and E,E-2,4-hexadienal were measured and used to derive effective quantum yields for photoisomerization of 0.36 +/- 0.04 for E-2-hexenal and 0.23 +/- 0.03 for E,E-2,4-hexadienal. Although photolysis appears to be an important atmospheric degradation pathway for E-2-hexenal and E,E-2,4-hexadienal, the reversible nature of the photolytic process means that gas phase reactions with OH and NO(3) radicals are ultimately responsible for the atmospheric removal of these compounds. Atmospheric photolysis of Z-3-hexenal produced CO, with a molar yield of 0.34 +/- 0.03, and 2-pentenal via a Norrish type I process. A value of j(Z-3-hexenal)/j(NO(2)) = (0.4 +/- 0.04) x 10(-2) was determined. The results suggest that photolysis is likely to be a minor atmospheric removal process for Z-3-hexenal.

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“…The NTII reaction in α, β-unsaturated carbonyls Of the enals, the photolysis of but-2-enal (crotonaldehyde) is the most experimentally studied. [84][85][86][87][88][89] None of these studies, however, have detected the enol and alkene photoproducts which would be expected from the NTII reaction, despite the low predicted S 1 and T 1 NTII photolysis thresholds shown in Figures 4 and 5. This can be rationalised by the inability of α, βunsaturated species to cleave their α, β-bond after formation of the 1,4-biradical.…”

Section: Discussionmentioning

confidence: 92%

“…Instead, photoisomerisation dominates the photolysis of but-2-enal. 85,88,89 Based on the inability of α, β-unsaturated species to undergo NTII reaction, and the high T 1 NTIa photolysis thresholds calculated for unsaturated species in earlier work, 49 ground state reactions and isomerisations are expected to dominate the photolysis of all α, β-unsaturated species.…”

Section: The Ntii Reaction In α β-Unsaturated Carbonylsmentioning

confidence: 94%

Structural Causes of Singlet/triplet Preferences of Norrish Type II Reactions in Carbonyls

Rowell

Kable²,

Jordan³

2020

Preprint

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Photolysis thresholds are calculated for the Norrish Type II (NTII) intramolecular γ-hydrogen abstraction reaction in 22 structurally informative carbonyl species. The B2GP-PLYP excited state S1 and T1 thresholds agree well with triplet quenching experiments. However, many linear-response methods deliver poor S1 energetics, which is explained by a S1/S0 conical intersection in close proximity to the S1 transition state. Multiconfigurational CASSCF calculations confirm a conical intersection features across all carbonyl classes. <div> </div><div>Structure–activity relationships are determined that could be used in atmospheric carbonyl photochemsitry modelling. This is exemplified for butanal, whose NTII quantum yields are too low when used as a ‘surrogate’ for larger carbonyls, since butanal lacks the γ-substitution that stabilises the 1,4- biradical. Reaction on T1 dominates only in species where the S1 thresholds are high — typically ketones. The α, β-unsaturated carbonyls cannot cleave the α–β bond, causing them to photoisomerise. A concerted S0 NTII mechanism is calculated to be viable and may explain the recent detection of NTII photoproducts in the photolysis of pentan-2-one below the T1 threshold.</div>

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Isomerization as a Primary Process in the Photolysis of Crotonaldehyde

Cited by 25 publications

References 0 publications

Chloroperoxidase-mediated oxidation of 1,3-butadiene to 3-butenal, a crotonaldehyde precursor

Chloroperoxidase-mediated oxidation of 1,3-butadiene to 3-butenal, a crotonaldehyde precursor

The atmospheric photolysis of E-2-hexenal, Z-3-hexenal and E,E-2,4-hexadienal

Structural Causes of Singlet/triplet Preferences of Norrish Type II Reactions in Carbonyls

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