Atmosphere monoterpene reaction

Atkinson, R., and S.M. Aschmann (1993), Atmospheric chemistry of the monoterpene reaction products nopinone, camphenilone, and 4-acetyl-1-methylcyclohexene, J. Atmos. Chem., 16, 337-348. 

Atkinson R, SM Aschmann, AM Winer, JN Pitts (1985a) Kinetics and atmospheric implications of the gas-phase reactions of NOj radicals with a series of monoterpenes and related organics at 294 2 K. Environ Sci Technol 19 159-163. 

As Barr et al. (2003) pointed out, the importance of such emissions is determined mainly by their impact on the three processes taking place in the atmosphere. The first consists in that such NMHCs as isoprene form in the course of carboxylization in plants and contribute much thereby to the formation of biospheric carbon cycle. The second process is connected with NMHCs exhibiting high chemical activity with respect to such main oxidants as hydroxyl radicals (OH), ozone (03), and nitrate radicals (N03). Reactions with the participation of such components result in the formation of radicals of alkylperoxides (R02), which favor efficient transformation of nitrogen monoxide (NO) into nitrogen dioxide (N02), which favors an increase of ozone concentration in the ABL. Finally, NMHC oxidation leads to the formation of such carbonyl compounds as formaldehyde (HCHO), which stimulates the processes of 03 formation. Finally, the oxidation of monoterpenes and sesquiterpenes results in the intensive formation of fine carbon aerosol with a particle diameter of <0.4 pm... 

The reactions observed in the photochemical smog, especially those concerning decomposition and oxidation of volatile organic substances, are accelerated by atmospheric aerosols, eg oxidation of some halogenated hydrocarbons, isoprene, monoterpenes, and aromatic hydrocarbons is enhanced by the surfaces of metal oxides, desert sand, volcanic ash, and sea salt [8],... 

Boyle, J.M., 1976. Atmospheric Reactions of Sulfur Dioxide and Monoterpenes. M.Sc. Thesis, The University of Calgary, Calgary, Canada, 97 pp. 

The monoterpenes react very rapidly with OH radicals (143), but since they also react rapidly with O3 (201, 202) their major atmospheric fate Is probably via reaction with O3, at the O3 levels encountered under most atmospheric conditions. 

Isoprenic units can be interconnected in different ways head-to-head, tail-to-tail, head-to-tail or tail-to-head. Oligomers of such isoprene units are called terpenes. A molecule with two isoprenes is named monoterpene, a molecule with four units is diterpene. Three isoprene monomers form sesquiterpenes. One of the most important terpenes is squalene, a primary metabolite that is present in all living organisms. In contact with the atmospheric oxygen, squalene is oxidized to squalene-oxide. In the reaction with the corresponding enzyme, squalene-oxide is folded into the conformation represented in the scheme below. 

Different mono- and sesquiterpenes have variable lifetimes in the atmosphere depending the other reactive compounds in the atmosphere. In atmospheres rich of oxides of nitrogen (NO ) volatile terpenes participate in the formation of ozone (O3). If the concentrations of NO are low, monoterpenes and sesquiterpenes react with O3 leading to lower concentratiOTi of phytotoxic O3. The reactiOTi products can be liquid or amorphic solid nano-scale particles which later aggregate into larger aerosol particles [12]. Reaction products of VOCs are called secmidaiy organic aerosol particles (SOA), because they are formed in the atmosphere from gases and fumes. 

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