AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Aqueous Reaction Rates of Hydroxyacetone with Ammonium Sulfate and Amines Measured by NMR as a Function of pH
MICHAEL SYMONS, Alyssa Rodriguez, Melissa Galloway, David De Haan, University of San Diego
Abstract Number: 651 Working Group: Aerosol Chemistry
Abstract Hydroxyacetone is a common tropospheric ketone because it is formed by oxidation of isoprene and biomass combustion. Reactions of hydroxyacetone in aqueous droplets and aerosol particles that contain ammonium salts and amines may be significant sources of secondary organic aerosol and brown carbon material. We report reaction rates of common atmospheric amines (glycine and methylamine) and ammonium sulfate with hydroxyacetone in D$_2O at room temperature over the pH range 3-7. Reaction mixtures of amines and hydroxyacetone were monitored by $^1H NMR over 12 or more hours. Data was normalized using internal standards acetonitrile (ACN) or dimethyl sulfoxide (DMSO). Hydroxyacetone + methylamine reaction rates increase with pH. Hydroxyacetone’s methyl group (2.13 ppm) reacts 2.5 times faster than the methylene group where OH is attached (4.36 ppm), indicating that aldol condensation occurs mainly via the methyl group. However, at pH 3.9 reaction the methyl and methylene groups occur at similar rates, within 10.0 percent. Additionally, we observed the formation of aromatic products.