AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Computational Study Probing the Potential Energy Surfaces of Acid Catalyzed Particle Phase Reactions
IVAN PILETIC, Edward Edney, Libero Bartolotti, U.S. Environmental Protection Agency
Abstract Number: 310 Working Group: Aerosol Chemistry
Abstract The role of acidity in the growth of aerosol particles has been shown to be significant. Frequently, acid catalyzed reactions in aerosols lead to the formation of larger and/or more polar molecules that are less volatile. We have used density functional theory to investigate acid catalyzed condensed phase reactions involving representative low molecular weight epoxides, alcohols, aldehydes and carboxylic acids. The calculations typically involved the incorporation of several explicit solvent molecules (water) for solvation and proton transfer purposes. Long range effects from the surrounding medium in the aerosol phase are simulated using a polarizable continuum model. Reaction barriers and possible intermediates are determined using a nudged elastic band method to locate transition states (saddle points) and stationary points (minima). Refinements of structural optimizations were carried out using the M062x density functional and the 6-311++G** basis set. Transition state theory was applied to estimate reaction rate constants. It is shown that acidic species such as H3O+ may lower reaction barriers by > 10 kcal/mol so that certain reactions such as the hydrolysis of epoxides proceed readily.