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Issue 44, 2006
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The atmospheric photolysis of E-2-hexenal, Z-3-hexenal and E,E-2,4-hexadienal

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Abstract

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(NO2) = (1.80 ± 0.18) × 10−2 and j(E,E-2,4-hexadienal)/j(NO2) = (2.60 ± 0.26) × 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 NO3 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(NO2) = (0.4 ± 0.04) × 10−2 was determined. The results suggest that photolysis is likely to be a minor atmospheric removal process for Z-3-hexenal.

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

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Publication details

The article was received on 07 Aug 2006, accepted on 27 Sep 2006 and first published on 10 Oct 2006


Article type: Paper
DOI: 10.1039/B611344C
Phys. Chem. Chem. Phys., 2006,8, 5236-5246

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

    M. P. O’Connor, J. C. Wenger, A. Mellouki, K. Wirtz and A. Muñoz, Phys. Chem. Chem. Phys., 2006, 8, 5236
    DOI: 10.1039/B611344C

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