Computational Studies of Atmospheric Chemistry Intermediates Keith T Computational Studies of Atmospheric Chemistry Intermediates Keith T. Kuwata, Chemistry Department, Macalester College, Saint Paul, MN, 55105 We have modeled the chemistry of the trans-2-butene primary ozonide A with MCG3//QCISD energies and RRKM theory. Figure 1 shows that the combined yields of thermalized acetaldehyde oxides (B and C) rise to almost 70% at 1 atm. Hydroperoxide D is a major non-photochemical OH source. We have also used variational transition state theory (based on MCG3//QCISD energies) to predict the reactivity of thermalized B and C under tropospheric conditions. B isomerizes to D with a rate constant of 24 s-1 at 298 K, and the reaction is very close to the high pressure limit at 1 atm. A Figure 1 C preferentially reacts with water to form a hydroperoxide (F) which will not decompose to form OH. The pseudo first order rate constant is 220 s-1 at 298 K and 24 Torr of H2O. PRF Type B Project Summary September 2009