O'Connor Margaret P, Wenger John C, Mellouki Abdelwahid, Wirtz Klaus, Muñoz Amalia
Department of Chemistry and Environmental Research Institute, University College Cork, Cork, Ireland.
Phys Chem Chem Phys. 2006 Nov 28;8(44):5236-46. doi: 10.1039/b611344c. Epub 2006 Oct 10.
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.
在西班牙巴伦西亚的大型户外欧洲光化学反应器（EUPHORE）中，对E-2-己烯醛、Z-3-己烯醛和E,E-2,4-己二烯醛的大气光解进行了研究。发现E-2-己烯醛和E,E-2,4-己二烯醛分别迅速异构化，生成Z-2-己烯醛和一种乙烯酮类化合物（可能是E-己-1,3-二烯-1-酮）。这两个异构化过程都是可逆的，反应物的形成略占优势。测定了j(E-2-己烯醛)/j(NO₂) = (1.80 ± 0.18) × 10⁻²和j(E,E-2,4-己二烯醛)/j(NO₂) = (2.60 ± 0.26) × 10⁻²的值。测量了E-2-己烯醛和E,E-2,4-己二烯醛的气相紫外吸收截面，并用于得出E-2-己烯醛光异构化的有效量子产率为0.36 ± 0.04，E,E-2,4-己二烯醛为0.23 ± 0.03。尽管光解似乎是E-2-己烯醛和E,E-2,4-己二烯醛重要的大气降解途径，但光解过程的可逆性意味着与OH和NO₃自由基的气相反应最终负责这些化合物的大气去除。Z-3-己烯醛的大气光解通过Norrish I型过程产生了CO，摩尔产率为0.34 ± 0.03，以及2-戊烯醛。测定了j(Z-3-己烯醛)/j(NO₂) = (0.4 ± 0.04) × 10⁻²的值。结果表明，光解可能是Z-3-己烯醛次要的大气去除过程。
