AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Atmospheric Reactions between Glycolaldehyde, Formaldehyde, and Ammonium Sulfate: A Product Identification Study
MELISSA GALLOWAY, Alyssa Rodriguez, Jeremy Kua, Katherine Millage, David De Haan, University of San Diego
Abstract Number: 347 Working Group: Aerosol Chemistry
Abstract Aqueous reactions of aldehydes with amines or ammonium salts have recently been implicated in atmospheric secondary organic aerosol and brown carbon formation processes. However, few of the reaction products, especially those responsible for visible light absorbance, have been characterized. Using a variety of techniques, including NMR spectroscopy and ESI-MS, the reaction products of small, water soluble aldehydes (e.g. formaldehyde and glycolaldehyde) with ammonium sulfate are identified. According to quantum-mechanical calculations, the most energetically stable product in the formaldehyde – ammonium sulfate reaction is hexamethylenetetramine, but many possible reaction pathways leading to local energy minima can produce other, less volatile nitrogen-containing compounds, many with alcohol functionalization. Experiments verify that hexamethylenetetramine is the major reaction product; this work seeks to verify the importance of these other reaction pathways. Similarly, glycolaldehyde and ammonium sulfate react to form colored solutions. Aqueous glycolaldehyde is found in both monomeric and dimeric forms. Evidence indicates that reaction products of glycolaldehyde – ammonium sulfate have the same equilibrium distribution; imines may be formed on glycolaldehyde monomer and dimer backbones before further reactions proceed. Product identification of these and similar reactions will allow for better understanding of the aqueous chemistry occurring in atmospheric cloud and aerosol droplets.