Dr. Heather A. Rypkema
Department of Atmospheric, Oceanic, and Space Sciences
University of Michigan
November 14, 2014
3:00 pm Chemical Sciences Building~ Room 101
Abstract:
Quantum chemical methods have a broad-ranging capacity toward informing our understanding of molecular transformations in a variety of environments, including the chemistry of the atmosphere. Specifically, these applications include kinetic and thermodynamic analysis of chemical reactions, evaluation of competing reaction channels, and the theoretical validation of postulated chemical mechanisms. This presentation provides a survey quantum chemistry as applied to a number of atmospherically relevant studies. The full atmospheric oxidation profile of peroxyacetic acid predicts the likely fate of a prevalent atmospheric species while postulating a new source of reactive species not represented in current models. The direct and catalyzed hydration of formic acid and acetaldehyde provide a mechanism for the formation of hygroscopic molecules capable of initiating cloud formation and the production of SOA. Diabatic excited states can be used to predict the relative reactivity among atom-transfer reactions, which are particularly significant in a hydroxyl-rich environment. A mechanism for the proliferation of atmospheric hydroxyl radical through the atmospheric oxidation of cyclical alkanes provides a possible explanation for the discrepancy between predicted and measured OH levels in the troposphere. Cumulatively, these studies will demonstrate the diverse applications of theoretical quantum chemistry in enhancing our understanding of atmospheric chemistry.