Hydrocarbon oxidation in the atmosphere: The basic rules and a few exceptions

PHYS 15

John J. Orlando, orlando@ucar.edu, Atmospheric Chemistry Division, NCAR, PO Box 3000, Boulder, CO 80307
Hydrocarbons, including saturated, unsaturated and substituted species, are emitted to the atmosphere from both biogenic and anthropogenic sources. Their atmospheric oxidation (initiated by photolysis, or by reaction with oxidants such as OH) leads to a complex array of intermediates, including carbonyls, alcohols, acids, nitrates, and multifunctional species. The oxidation of essentially all hydrocarbons follows a now familiar pattern, involving the chemistry of alkyl, peroxy, and alkoxy radicals. While this general pattern is well established, it is also the case that subtle changes in radical structure leads to changes in the energetics, thus controlling the rates and branching to various processes and ultimately controlling the environmental impact of the chemistry. In this presentation, the basic peroxy and, in particular, alkoxy radical chemistry will first be outlined. This will be followed by a discussion of some recent data on ether and iodocarbon oxidation, which illustrate situations where more exotic pathways occur.