Abstract View
Condensed Phase Reactions of Carboxynitrates with Alcohols to Form Esters: Measurements of Kinetics and Equilibria
HANNAH MABEN, Paul Ziemann, University of Colorado Boulder
Abstract Number: 372
Working Group: Aerosol Chemistry
Abstract
Organic aerosols decrease visibility and negatively impact human and environmental health. Secondary organic aerosol (SOA) is formed from the partitioning of the oxidation products of volatile organic compounds (VOCs) that are emitted into the atmosphere from biogenic or anthropogenic sources. These products can undergo particle-phase reactions, which impact the formation, composition, and chemical-physical properties of aerosols. While these reactions are known to occur in the atmosphere, models and data describing their kinetics and equilibria are sparse. To investigate one of these reactions, a synthesized probe compound was used to measure the kinetics and equilibria for the formation of an ester from the reaction of a C11 carboxynitrate with 1-octanol. The disappearance of the carboxynitrate and the formation of products was monitored using HPLC-UV, and product identity was confirmed using ESI-MS and ATR-FTIR. The probe compound was mixed with 1-octanol and the reaction was monitored over 24 hours to determine the rate and equilibrium constants. Then, to study the effects of an acid catalyst, the same experiment was conducted with added sulfuric acid, first diluted in acetonitrile to maintain a single organic phase and then in water for an organic/aqueous phase-separated reaction. The carboxynitrate did not react with 1-octanol in a single organic phase reaction, but ester formation was observed when sulfuric acid was added both in a single organic phase and in a phase-separated reaction. Based on the results, the forward and reverse rate constants and equilibrium constant were determined. These results provide useful insights into the types of oligomerization reactions that are likely to occur in atmospheric aerosols, and rate and equilibrium constants that can be added to models to better predict transformations of SOA in the atmosphere.