Crotonaldehyde photolysis

Trans-2-Butenal (trans-Crotonaldehyde). Pitts and coworkers (2,58) investigated the photolysis of trans-crotonalde-hyde in the gas phase to correlate the structural effects on photodecomposition and reactivity of a, (5-unsaturated aldehydes. As in the case of acrolein, this molecule showed an unusual stability, except polymerization being the only significant reaction at 265-254 nm and 25°C (2). Some reactions giving... 

Acrolein and crotonaldehyde are the representatives of the group of unsaturated aldehydes. Though these aldehydes show some similarities, with respect to their photochemical behaviour, to the aldehydes discussed previously, they differ from them in many respects. While the rate of photolysis is significant only at short wavelengths or at high temperatures, the occurrence of the polymerization processes is independent of the energy available. Fluorescence was not observed with either of these compounds. 

Magneron, I., R. Thdvenet, A. Mellouki, Q. Le Bras, G.K. Moortgat and K. Wirtz A study of the photolysis and OH-initiated oxidation of acrolein and rrani-crotonaldehyde, J. Phys. Chem. A 106 (2002) 2526. 

In the present work a large set of actinic spectra recorded in the EUPHORE chamber under various atmospheric conditions has been obtained and used for the calculation of photolysis frequencies of 17 organic carbonyl compounds. From a statistical analysis of the photolysis frequencies calculated for the compounds an analytical form for Jfd) has been derived. For unsaturated compounds (methyl vinyl ketone, methacrolein, acrolein and crotonaldehyde) < ) g is negligible, although those cxompounds possess absorption spectra reaching the near visible. 

These compounds, exemplified by acrolein, crotonaldehyde, and methyl vinyl ketone, are known to react with ozone and with OH radicals. Photolysis and N03 radical reaction are of minor importance. Under atmospheric conditions the 03 reactions are also of minor significance (Atkinson and Carter, 1984), leaving the OH radical reaction as the major loss process. For the aldehydes, OH radical reaction can proceed via two reaction pathways OH radical addition to the double bond and H-atom abstraction from the -CHO group (Atkinson, 1989). For crotonaldehyde, for example, the OH reaction mechanism is given in Fig. 3. As can be noted from Fig. 3, these a,/3-unsaturated aldehydes are expected to ultimately give rise to a-dicarbonyls such as glyoxal and methylglyoxal. For the a,/3-unsaturated ketones such as methyl vinyl ketone, the major... 

During the day, the destruction of crotonaldehyde is controlled primarily by reaction with OH. The photolysis lifetime is 1.8 days for an overhead Sun see chapter IX. For [OH] = 2.5 X10 molecule cm, the lifetime with respect to reaction with OH is about 3 h. The lifetime for nighttime removal by NO3, with [NO3] 3 x 10 moleculecm ... 

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