Acrolein photolysis

Photolytic. Photolysis products include carbon monoxide, ethylene, free radicals, and a polymer (Calvert and Pitts, 1966). Anticipated products from the reaction of acrolein with ozone or OH radicals in the atmosphere are glyoxal, formaldehyde, formic acid, and carbon dioxide (Cupitt,... 

Photolytic. Atkinson (1985) reported a rate constant of 2.59 x 10 " cmVmolecule-sec at 298 K. Based on an atmospheric OH concentration of 1.0 x 10 molecule/cm , the reported half-life of allyl alcohol is 0.35 d. The reaction of allyl alcohol results in the OH addition to the C=C bond (Grosjean, 1997). In a similar study, Orlando et al. (2001) studied the reaction of allyl alcohol with OH radicals at 298 K. Photolysis was conducted using a xenon-arc lamp within the range of 240-400 nm in synthetic air at 700 mmHg. A rate constant of 4.5 x 10 " cm /molecule-sec was reported. Products identified were formaldehyde, glycolaldehyde, and acrolein. 

Intermediate A reacts with conjugated carbonyl compounds to give 1 1 adducts (92). Reaction of the intermediate produced from p-tolylpenta-methyldisilane with methyl vinyl ketone affords 2-trimethylsilyl-4-methyl(methylallyloxydimethylsilyl)benzene in 51% yield as the sole volatile product. Acrolein also reacts with phenylpentamethyldisilane under similar photolysis conditions to give 2-trimethylsilyl-4-methyl(allyloxydi-... 

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. 

At room temperature, Thompson and Linnett found the decomposition quantum yield to be 10 and 10 at 3665 and 3135 A, respectively. Placet et al. observed photolysis only with unliltered light of the mercury arc. To explain the photochemical stability of acrolein, Thompson and Linnett assume that delocalization of energy rapidly occurs in the excited molecule formed as the result of light absorption. The conjugated double bond system of the molecule may be responsible for the rapid internal degradation of the energy. 

Irradiation of allyl azide produced the imine of acrolein but photolysis of l-azido-2-phenylprop-2-ene (63) in cyclohexane solution resulted in a small yield of the azacyclobutane (64) and 2-phenyl-propenalimine (65) . This is the first observation of an 1-azabi-cyclo [1.1.0]-butane ring in the products of photodecomposition of an allylic azide. 

Irradiation of propylene and 02-loaded zeolite BaY at room temperature with green or blue light induced partial oxidation of the olefin [18]. Readily identified products were acrolein, allyl hydroperoxide, and propylene oxide. The hydroperoxide was found to be stable when the zeolite was kept at -100°C. Hence, photolysis experiments at this temperature allowed us to find out about the origin of the aldehyde and epoxide. Allyl hydroperoxide was the main product at -100°C, the remaining 13% were propylene oxide. Warm-up of the zeolite after photo-accumulation of the hydroperoxide produced propylene oxide if excess propylene was kept in the matrix, but only acrolein if the olefin was removed prior to warm-up. Hence, allyl... 

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. 

Concerning the molecular products of butenedial photolysis (Figure 3), the yield of 2(5H)-furanone is well predicted by the simulation, glyoxal and maleic anhydride are overpredicted while the CO yield in the simulation is much lower than observed experimentally. In MCMv3.1 glyoxal and CO are formed as co-products (Figure 4), but this is not consistent with the different yields of these products observed experimentally. Thuener et al. (2003) include a different source of CO in their proposed mechanism, i.e. direct formation fi om photolysis with a yield of 20%. A possible co-product for direct CO production is acrolein formed by an H-shift and C-C cleavage. The acrolein concentration was below the detection limit of the measurement technique, and its maximum yield was estimated to be 10%. No other direct photolysis products were observed and it was not possible to positively determine the mechanism and co-products for CO formation. 

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... 

CH3CHCO was also photolyzed in quartz (X > 200 nm). The CO population distribution of the higher vibrational levels was distinctly hotter than was statistically expected. Photolysis of the isomeric acrolein (CHjCHCHO) under similar conditions gave rise to a distribution very similar to that obtained for CH3CHCO. (No dissocation of acrolein could be measured in Vycor.) These results have been tentatively explained by the occurrence of a new reaction channel at <200 nm, conunon to both isomers, which leads to the direct elimination of C2H4 from the complex. 

Photolytic. Photolysis products include carbon monoxide, ethylene, free radicals and a polymer (Calvert and Pitts, 1966). Anticipated products from the reaction of acrylonitrile with ozone or hydroxyl radicals in the atmosphere are glyoxal, formaldehyde, formic acid and carbon dioxide (Cupitt, 1980). The major product reported from the photooxidation of acrolein with nitrogen oxides is formaldehyde with a trace of glyoxal (Altshuller, 1983). Osborne et al. (1962) reported that acrolein was stable at 30°C and UV light (2. = 313 nm) in the presence and absence of oxygen. 

During the day, the destruction of acrolein is controlled primarily by photolysis and reaction with OH. The photolysis lifetime is about 8 days for an overhead Sun see chapter IX. For [OH] 2.5 x 10 moleculecm , its lifetime with respect to reaction with OH is about 5 h. 

Figure IX-C-7. The fraction of the photodecomposition of acrolein that is estimated to occur hy the various primary photodecomposition modes data of Gai dner et al. (1987) from the photolysis studies at 313 nm and 25°C. The gray-dashed hne marks the concentration of air at 1 atm. pressure and 298 K. 

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