Atmospheric chemistry halogen compounds

The presence of ionizing radiation in the upper regions of the earth s atmosphere and the realization that atmospheric chemistry can occur on the surface of ice and dust particles have lead many authors to study on the interaction of LEE with molecular solids of ozone [203], HCl [236], and halogen-containing organic compounds [176,177,195-197,199-202,205,214,217,224-234] in an effort to shed new light on the problem of ozone depletion. In a recent series of experiments, Lu and Madey [297,298] found that the and CG yields... 

Barbara J. Finlayson-Pitts is Professor of Chemistry at the University of California, Irvine. Her research program focuses on laboratory studies of the kinetics and mechanisms of reactions in the atmosphere, especially those involving gases with liquids or solids of relevance in the troposphere. Reactions of sea salt particles to produce photochemically active halogen compounds and the subsequent fates of halogen atoms in the troposphere are particular areas of interest, as are reactions of oxides of nitrogen at aqueous and solid interfaces. Her research is currently supported by the National Science Foundation, the Department of Energy, the California Air Resources Board, the Dreyfus Foundation, and NATO. She has authored or coauthored more than 80 publications in this area, as well as a previous book, Atmospheric Chemistry Fundamentals and Experimental Techniques. 

Midgley, P.M. and McCulloch, A. (1999c) International regulations on halocarbons, in P. Fabian and O.N. Singh (eds.), Reactive Halogen Compounds in the Atmosphere, The Handbook of Environmental Chemistry Vol. 4E, Springer, Berlin, pp. 203-221. 

In all there are about seventy different haloalkane species which have been detected in the atmosphere, together with more than twenty haloalkenes, nearly one-hundred halo-genated cycloalkane and aromatic compounds and about forty halogenated pesticides10. In view of their greater abundances, this review will focus upon the atmospheric chemistry of CFCs, HCFCs and HFCs. 

Studies of the reactions of many atmospherically important atomic and free radical species were described in Section 9 this Section deals primarily with important molecular species. A brief review of the progress achieved recently in the field of atmospheric chemistry has been provided by Cox, " with emphasis on the reactions of O3 and important H-, N-, C-, halogen-, and S-containing species. Waynehas reviewed extraterrestrial atmospheric photochemistry and Strobel " has reviewed the photochemistries of the atmospheres of Jupiter, Saturn, and Titan. Kaye and Strobeldescribed a 1-dimensional photochemical model of PHj chemistry in the atmosphere of Saturn. A study of the photochemical reactions of H2O and CO in the Earth s primitive atmosphere has been presented by Bar-Nun and Chang. " They concluded that even if the primitive atmosphere initially contained no H2 and contained carbon only in the form of CO and CO2, photochemical processes would have enriched the environment with a variety of organic compounds. 

Clearly reactions (2), (3), (4) and (5) could all play significant roles in the atmospheric degradation of halogenated organic compounds. Kinetic data for reactions (3), (4) and (5) are needed for a more complete understanding of the atmospheric chemistry for halogenated organic compounds. 

The perhalosilanes X4Si (X = F, Cl, Br, or I), the higher perhalosilanes, and compounds containing mixtures of halogens are all reactive compounds (as would be expected from the chemistry of the halohydrosilanes described above in Section 5.2.3) that hydrolyze readily to give HX in the atmosphere they therefore require care in handling, preferably under a blanket of inert gas. The chloride CLiSi is by far the most widely used of these compounds and is available on a large scale. 

---