Water effects on atmospheric reactions
Abstract
Water is the third most abundant molecule in the atmosphere behind nitrogen and oxygen. Up until recently the atmospheric community has considered water only as a greenhouse gas. It has been shown that although water does not readily react under atmospheric conditions, water does have the ability to form hydrogen bonded complexes with other atmospheric species. The formation of these complexes can drastically change the chemistry of said atmospheric species. The work presented in this thesis displays the effects that water has on photochemical reactions, radical molecule reactions, as well as radical isomerization reactions that are of great interest to atmospheric chemistry. The potential energy surfaces of these reactions with and without water are obtained using ab initio methods. Furthermore, reaction rates are calculated utilizing numerous kinetic theories to understand the catalytic potential of water, specifically under atmospheric conditions. Firstly, the photodecomposition of CF3OH, an atmospheric by-product of Hydrofluorocarbons (HFCs), is studied. Here, water is shown to open a plausible route of photodecomposition, where there was none before. Also discussed are the potential catalytic effects and new reactions as a result of the introduction of a single water molecule to several radical-molecule reactions, including HOCl + OH, H2O2 + OH, and HCl + OH reactions. In these reactions, catalysis is seen with the introduction of water; however the significance of these reactions strongly depends on the formation of water-molecule or water-radical complexes. Interchange reactions between complexes are also seen in the HOCl and H2O2 system. Lastly, the potential for hydrogen bonding molecules, specifically atmospheric acids to act as catalysts in radical isomerization reactions is also examined.
Degree
Ph.D.
Advisors
Francisco, Purdue University.
Subject Area
Atmospheric Chemistry|Inorganic chemistry|Physical chemistry
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