Quelques Aspects de la Chimie des Aldehydes dans la Basse Troposphere

Gas-phase rate coefficients and activation energies for the reaction of NO3radicals with selected branched aliphatic aldehydes

“…33,34 The value calculated by Ullerstam et al for the reaction with 2-methylpropanal is lower (14 AE 1 kJ mol À1 ) than that obtained in this work for the reaction of this compound and lower than the activation energy for the other reactions of different saturated aldehydes reported in the literature. [24][25][26][27][28][29][30][31][32][33]42 For a better understanding of the reactivity of aldehydes with NO 3 it is necessary to analyze the result obtained in this work together with those obtained for other series of aldehydes. Table 2 shows the room temperature rate coefficient and activation energy for different aldehydes, obtained in our laboratory.…”

“…The values of rate coefficients and activation energies obtained in the present work appear entirely consistent with the available literature data for the reactions of the NO 3 radical with other aliphatic aldehydes. [24][25][26][27][28][29][30][31][32][33]42 All the data available for these reactions indicate that the reaction with aliphatic aldehydes is an overall abstraction process but not only a simple H-abstraction process. The reaction could proceed via the formation of an exothermic adduct before C-H ald bond cleavage and the subsequent elimination of nitric acid.…”

“…1,2 They are emitted as primary pollutants from partial oxidation of hydrocarbon fuels and they are the first stable products (secondary pollutant) from the atmospheric oxidation of different anthropogenic and biogenic organic compounds. [3][4][5] Also vegetation has been found to be a significant source of aldehydes, mainly high molecular weight aldehydes ( > C 5 ), emitted from a variety of arboreous plants, shrubs, herbaceous plants and mosses. 6,7 Depending on the plant species, the emission rates can be comparable to those of monoterpenes.…”

“…20,21 Aldehydes are removed from the troposphere by wet and dry deposition, photolytic processes yielding radicals as primary products or by chemical reactions with the OH radical during the day-time or by reaction with the NO 3 radical during the night-time. The night-time reactions of NO 3 radicals with aldehydes have been object of several kinetic studies, [22][23][24][25][26][27][28][29] but, at the present time, kinetic data are still scarce especially for larger aldehydes ( > C 5 ). [30][31][32][33][34] These reactions lead to the formation of hydroperoxy (HO 2 ) and organic peroxy (RO 2 ) radicals, and in the presence of NO to the formation of OH.…”

Rate coefficients and Arrhenius parameters for the reaction of the NO3 radical with acetaldehyde and acetaldehyde-1d

“…2 The remaining four studies are relative rate measurementsÈthree are relative to the NO 2 equilibrium,3h5 which is strongly tem-] NO 3 H N 2 O 5 perature dependent7h9 and one is a preliminary study relative to ethene. 6…”