Acetaldehyde atmospheric chemistry

Detailed structural calculations have been carried out for this system. This is because the neutral isomer, C2HsO, which is implicated in the thermochemistry of ethanol, is of interest in pollution control, atmospheric chemistry, and combustion. Also, there is new information available from photoionization experiments with which to compare theoretical calculations. For details of these comparisons, see Curtiss et al.73 In the earlier theoretical studies of Nobes et al.,74 calculations were performed at the MP2 and MP3 levels with basis sets of double plus polarization (6-13G ) with electron correlation. These studies revealed four stable minima for the system protonated acetaldehyde, CHj-C H-OH <-> CH3-CH=0+H the methoxymethyl cation, CH3OCH2 protonated oxirane, (CH2)2OH+ and vinylox-... 

Grosjean et al. (1996) investigated the atmospheric chemistry of cyclohexene with ozone and an ozone-nitrogen oxide mixture under ambient conditions. The reaction of cyclohexene and ozone in the dark yielded pentanal and cyclohexanone. The sunlight irradiation of cyclohexene with ozone-nitrogen oxide yielded the following carbonyls formaldehyde, acetaldehyde, acetone, propanal, butanal, pentanal, and a C4 carbonyl. 

In addition to the role of atmospheric reactions in the fate of airborne FLAPs, atmospheric chemistry also plays a role in the formation of some of them, most notably formaldehyde and acetaldehyde. Thus, the potential formation of such compounds from the oxidation of precursors in the atmosphere must also be taken into account in their risk assessments. 

Grosjean, D., Atmospheric Chemistry of Toxic Contaminants. 2. Saturated Aliphatics Acetaldehyde, Dioxane, Ethylene Glycol Ethers, Propylene Oxide, J. Air Waste Manage. Assoc., 40, 1522-1531 (1990b). 

Sinha, V, J. Williams, M. Meyerhofer, U. RiebeseU, A. I. Paulino and A. Larsen (2007) Air-sea fluxes of methanol, acetone, acetaldehyde, isoprene and DMS from a Norwegian fjord following a phytoplankton bloom in a mesocosm exp>eriment. Atmospheric Chemistry and Physics 7, 739-755... 

With respect to carbonylation chemistry Sakakura and Tanaka have shown that irridiation of rhodium complex RhCl(CO)(PMe3)2 in pentane as solvent under a CO atmosphere (1 bar) at ambient temperature gives rise to carbonylated products. Selectivity for linear aldehyde is > 98 % (eq. (11)) [45]. This insertion reaction is photochemically driven, since it is known that aldehyde decarbonylation is a thermodynamically favorable process. Other photochemial C-H activation reactions have been investigated [46]. When toluene is reacted in the presence of CO and the same Rh complex, phenyl acetaldehyde is obtained as the major product (eq. (12)) [47]. 

The vinoxy CH2CHO and 1-methylvinoxy (acetonyl) radicals are key intermediates in the mechanisms of many reactions of importance for atmospheric and combustion chemistry. The formation of vinoxy radicals has been observed in several chemical processes. They may be formed in reactions of OH radicals with ethylene oxide (C2H4O) and with acetylene (C2H2) in the presence of 02.8 They are also produced in reactions of 0(3P) atoms with alkenes and in the reactions of reactive atoms such as F or 0(3P) with acetaldehyde.164,165 The 1-methylvinoxy (acetonyl) radical CH2C(CH3)0 is considered an important intermediate in the atmospheric oxidation of acetone initiated by the OH radical.166171 Spectroscopic studies by Washida et al.164 and Williams et al.m allow estimation of the rate constant for the reaction of acetonyl with 02. 

Doussin, J.R, B. Picquet-Varranlt, R. Durand-Jolibois, H. Loirat, and P. Carlier (2003), A visible and FTIR spectrometric study of the nighttime chemistry of acetaldehyde and PAN nnder simulated atmospheric conditions, J. Photochem. Photobiol. A., 157, 283-293. 

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