RUI: Computational Modeling of Hydroxyl Radical and Carboxylic Acid Formation in the Atmosphere

Macalester College, Saint Paul MN

Investigators

Abstract

This project is funded by the Environmental Chemical Sciences Program in the Division of Chemistry at the National Science Foundation. Professors Keith T. Kuwata of Macalester College and Professor Stacey A. Stoffregen of the University of Wisconsin-River Falls and their undergraduate research students are developing more accurate and detailed theoretical models of chemical reactions in the atmosphere. The most significant broader impact of the project is the training that Macalester and River Falls undergraduates receive to conduct significant research in atmospheric chemistry, which in turn equips them to pursue advanced study in STEM fields. This research also contributes to the intellectual vitality of the Midwest Undergraduate Computational Chemistry Consortium (MU3C), to which both Professor Kuwata and Professor Stoffregen belong. Their students will make presentations on their research projects at the in-person MU3C conference every summer and the on-line MU3C conference every winter. MU3C membership gives the PIs and their students opportunities to interact with fellow computational chemistry faculty and students at nine other primarily undergraduate institutions at conferences twice a year. The project focuses on clarifying the impacts that intermediates in hydrocarbon oxidation reactions have on free radical and carboxylic acid concentrations. One intermediate of interest is the vinyl hydroperoxide (VHP) formed in atmospheric alkene ozonolysis. Current experimental and theoretical studies suggest that the tendency of the VHP to undergo homolysis to form OH varies with both the size and structure of the original alkene and with atmospheric conditions. Understanding these variations requires more creativity about possible VHP chemical reactions and the application of quantum chemical methodology that can accurately model molecules with substantial static electron correlation. Such models provide new mechanistic insights about atmospheric processes by making predictions about transient species that cannot be directly characterized experimentally. At the same time, these models are also used to predict experimentally known quantities such as the concentrations of stable atmospheric species. Comparisons between theory and experiment both validate theoretical predictions and drive the development and application of new theoretical methods.