The influence of hydrogen bonding on the atmospheric chemistry of peroxy and carboxylic acids

University Of California-San Diego, La Jolla CA

Investigators

Abstract

In this project funded jointly by the Chemical Structure, Dynamics and Mechanisms A Program of the Division of Chemistry and the Atmospheric Chemistry Program in the Division of Atmospheric and Geospace Sciences, Professor Amitabha Sinha of University of California San Diego investigates the role played by hydrogen bonding in influencing the chemistry of oxygenated organic molecules of atmospheric importance. Organic molecules released into the atmosphere through anthropogenic and biogenic activity undergo reactions that result in the formation of oxidized products. The enhanced polar character of these oxidized products results in their ability to interact through hydrogen bonding. Although weak, hydrogen bonds are pervasive. Investigating the subtle impact of hydrogen bonding on the chemistry of oxygenated organics contributes to improving our understanding of atmospheric processes that control urban air quality as well as atmospheric radiative balance. In addition, the research permits the training and education of students at the graduate and undergraduate. The project also provides opportunities for high school students and students from underrepresented groups to be exposed to university research. In this work, vibrational overtone excitation combined with laser induced fluorescence detection, kinetic analysis, and computational chemistry is used to investigate the impact of hydrogen bonding on the chemistry of several oxygenated organic molecules. In the first phase of the work the impact of intramolecular hydrogen bonding on the vibrational photochemistry and unimolecular dissociation dynamics of peroxyacids is probed. In the second phase of the study the ability of carboxylic acids to promote hydrogen atom transfer reactions through intermolecular hydrogen bonding is investigated. Organic acids are ubiquitous in the atmosphere as they are byproducts of hydrocarbon oxidation. Their ability to catalyze hydrogen atom transfer reactions makes them an important contributor to various atmospheric processes including aerosol growth.