Abstract View
Automating the Search for New Pathways in Atmospheric Oxidation Chemistry
VICTORIA BARBER, Jesse Kroll, MIT
Abstract Number: 244
Working Group: Aerosol Chemistry
Abstract
Understanding the routes by which secondary organic aerosol (SOA) is formed via oxidation of volatile organic compounds represents a key challenge in atmospheric chemistry. In recent years, a number of "exotic" transformations not typically found in standard atmospheric oxidation mechanisms (e.g. Peroxy radical isomerization, epoxide formation) have been shown to be important in the formation of low-volatility organic compounds and SOA. These discoveries suggest that there may be other non-traditional mechanisms that play a role in oxidative aging and aerosol formation, and point to the need for a systematic way to look for such pathways. The Reaction Mechanism Generator (RMG) is an open-source program developed for and typically applied to combustion systems. RMG uses a combination of an extensive database of known chemical information and a functional group based methodology for kinetic and thermodynamic parameter estimation to automatically develop reaction networks with very little a priori information. Here, we use RMG to systematize and automate the search for new mechanisms in atmospheric organic oxidation chemistry. RMG is used to generate reaction networks for the OH-intiated oxidation of a set of approximately 200 monofunctionally and bifunctionally substituted pentanes in the gas phase at atmospheric temperatures and pressures. In addition to the canonical reactions expected for organic radicals in the atmosphere, a number of "exotic" reactions are identified. These include the recently explored but historically underappreciated reaction mechanisms described above, as well as examples of novel chemistry which may impact SOA formation. The results demonstrate the utility of RMG as a tool for atmospheric reaction discovery, and provide several interesting targets for further study via quantum mechanical calculations and experiments.