Identifying and Quantifying Products Formed from the Reaction of Alkenoic Acids with OH Radicals in a Low NOx Environment
ANNA ZIOLA, Paul Ziemann,
University of Colorado Boulder Abstract Number: 226
Working Group: Aerosol Chemistry
AbstractData from two Los Angeles field campaigns, CalNex in 2010 and LAAQS in 2020, show that the concentration of mid-day NO, a prominent component in VOC (volatile organic compound) oxidation mechanisms, has decreased by about 75%. While many studies have detailed how VOCs behave in high NOx environments and how these reactions contribute to aerosol formation, there is less information about these VOC mechanisms in the absence of or lower concentrations of NOx. To learn about this low NOx behavior and its contribution to aerosol formation, we reacted a 1-alkene with a terminal carboxylic acid, 3-butenoic acid and 5-hexenoic acid, with OH radicals while using an iodide chemical ionization mass spectrometer (I-CIMS) to identify the products. We used this carboxylic acid functional group tag because an I-CIMS is very sensitive to carboxylic acids, allowing us to easily detect both the reactant and the products. Once we identified the products, we synthesized standards of the resulting products to calibrate the I-CIMS and quantify them. This enabled us to determine mechanistic branching ratios and rate constants of the reaction. By comparing two systems with different carbon numbers and taking advantage of carboxylic acid properties, we were able to elucidate the mechanism and branching ratios of a 1-alkene and OH radical reaction in a low NOx environment and better understand its contribution to aerosol formation.