We introduce a novel Computational Brewing Approach (COBRA) to model oligomerization chemistry stemming from repetitive condensation and addition reactions of monomers in isoprene photooxidation organic aerosols. COBRA takes two sets of data as input: a list of the initial chemical structures making up the starting molecular pool, and a list of reaction rules defining potential chemical transformations within the system.  The reactions are propagated through several iterations, with products of previous iterations serving as reactants for the next one. A set of four reactions including esterification, aldol condensation, and hemiacetal formation, along with 27 seed molecules, were used to predict products of oligomerization in isoprene photooxidation secondary organic aerosol (SOA). The simulation generated thousands of unique structures in the mass range of 120-500 Da, and correctly predicted greater than 70% of the peaks observed by high-resolution mass spectrometry (HR-MS) of isoprene SOA. Selected structures predicted by the simulation were confirmed with tandem mass spectrometry (MSn). The model aids in structure elucidation from tandem mass spectrometry by offering up to a 100-fold reduction in the number of possible isomers for a given molecular formula. COBRA is not limited to atmospheric aerosol chemistry; it can also be applied to the prediction of reaction products in other environmental complex mixtures for which reasonable reaction mechanisms and seed molecules can be supplied by experimental or theoretical methods.

COBRA: Computational brewing approach to predicting the molecular composition of organic aerosols

243rd National Meeting (2012)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.