Presentation Title

Pathway Validation for the Photooxidation of Atmospherically Relevant Dicarboxylic Acids: Role of Photolysis Time on Temporal Profiles

Faculty Mentor

Paula K Hudson

Start Date

23-11-2019 9:15 AM

End Date

23-11-2019 9:30 AM

Location

Markstein 203

Session

oral 1

Type of Presentation

Oral Talk

Subject Area

physical_mathematical_sciences

Abstract

Aerosol particles contribute to chemical reactions in the atmosphere. The composition of aerosol particles is initially dependent on the source (e.g., from anthropogenic (man-made) or biogenic (natural) sources) of which dicarboxylic acids are 2 %, a significant percentage, of total aerosol mass.. After generation, aerosol can react and change composition in the atmosphere through chemical and light initiated (photolysis) reactions. To better understand the atmospheric effect of aerosol, it is important to identify both the starting material and reaction products that form. Further, if the process of converting starting materials to reaction products, the reaction mechanism is understood, reaction products can be predicted from given starting materials. Previous studies have proposed reaction mechanisms for the formation of seven reaction products from the photooxidation of succinic acid (SA), a dicarboxylic acid, through a combination of hydrogen abstraction, carbon-carbon bond cleavage, and radical-radical recombination. In this study, a similar 120 min. time dependent photooxidation experiment was conducted with glutaric (GA) and adipic (AA) acids, longer chain dicarboxylic acids, removing samples for analysis at t=0, 5, 15, 30, 60, 90, and 120 min. It is proposed that the analogous reactants (SA, GA and AA) should follow similar reaction mechanisms resulting in the formation of "equivalent" reaction products. Liquid chromatography coupled to a mass spectrometer (LC-MS) was used to identify the composition of equivalent reaction products by comparing proposed to exact measured masses. This data is then used to construct temporal profiles allowing us to see the growth over time of the mechanism predicted product and determine mechanism validation. While many proposed mechanisms are conserved between reactants, the proposed position of carbon-carbon bond cleavage pathways is affected by the number of carbon atoms of the dicarboxylic acid whether odd / even or total carbon chain length.

This document is currently not available here.

Share

COinS
 
Nov 23rd, 9:15 AM Nov 23rd, 9:30 AM

Pathway Validation for the Photooxidation of Atmospherically Relevant Dicarboxylic Acids: Role of Photolysis Time on Temporal Profiles

Markstein 203

Aerosol particles contribute to chemical reactions in the atmosphere. The composition of aerosol particles is initially dependent on the source (e.g., from anthropogenic (man-made) or biogenic (natural) sources) of which dicarboxylic acids are 2 %, a significant percentage, of total aerosol mass.. After generation, aerosol can react and change composition in the atmosphere through chemical and light initiated (photolysis) reactions. To better understand the atmospheric effect of aerosol, it is important to identify both the starting material and reaction products that form. Further, if the process of converting starting materials to reaction products, the reaction mechanism is understood, reaction products can be predicted from given starting materials. Previous studies have proposed reaction mechanisms for the formation of seven reaction products from the photooxidation of succinic acid (SA), a dicarboxylic acid, through a combination of hydrogen abstraction, carbon-carbon bond cleavage, and radical-radical recombination. In this study, a similar 120 min. time dependent photooxidation experiment was conducted with glutaric (GA) and adipic (AA) acids, longer chain dicarboxylic acids, removing samples for analysis at t=0, 5, 15, 30, 60, 90, and 120 min. It is proposed that the analogous reactants (SA, GA and AA) should follow similar reaction mechanisms resulting in the formation of "equivalent" reaction products. Liquid chromatography coupled to a mass spectrometer (LC-MS) was used to identify the composition of equivalent reaction products by comparing proposed to exact measured masses. This data is then used to construct temporal profiles allowing us to see the growth over time of the mechanism predicted product and determine mechanism validation. While many proposed mechanisms are conserved between reactants, the proposed position of carbon-carbon bond cleavage pathways is affected by the number of carbon atoms of the dicarboxylic acid whether odd / even or total carbon chain length.