Measurements of the Temperature Dependence of the Rate Constant of the Reaction of Hydroxyl Radical and Acetic Acid and its Deuterated Isotopomers Between Temperatures 263-373K

HR: 0800h
AN: A51C-0082 [Abstracts]
TI: Measurements of the Temperature Dependence of the Rate Constant of the Reaction of Hydroxyl Radical and Acetic Acid and its Deuterated Isotopomers Between Temperatures 263-373K
AU: * Vimal, D
EM: dvimal@indiana.edu
AF: School of Public & Environmental Affairs, 1315 E 10th St, Bloomington, IN 47405 United States
AU: Stevens, P S
EM: pstevens@indiana.edu
AF: School of Public & Environmental Affairs, 1315 E 10th St, Bloomington, IN 47405 United States
AU: Stevens, P S
EM: pstevens@indiana.edu
AF: Department of Chemistry, 800 E. Kirkwood Ave., Bloomington, IN 47405 United States
AB: Acetic acid is ubiquitous in the earth's atmosphere where it has a global source strength of ~ 75 Tg yr^-1 from secondary photochemical reactions and ~ 48 Tg yr^-1 from direct emissions due to biomass burning. It contributes significantly to the acidity of natural waters and plays an important role in determining OH and HO₂ radical budgets and ultimately affecting the oxidative capacity of troposphere. Acetic acid is removed from the atmosphere primarily by wet and dry deposition and by reaction with hydroxyl (OH) radical. However, current atmospheric chemistry models are not able to accurately reproduce acetic acid concentrations suggesting a gap in our understanding of its sources and sinks. We present low pressure (~ 5 Torr) measurements of the rate constant of the reaction of acetic acid with OH in the temperature range of 263-373K, using the discharge flow techniques coupled with resonance fluorescence detection of OH radicals. Our measured value of the rate constant of (7.37 ± 0.34) × 10^-13cm³molecule^-1s^-1 at 298K is in good agreement with previous studies. At low pressure, the reaction displays a negative temperature dependence consistent with previous studies conducted at higher pressures. A primary kinetic isotope effect was observed while comparing the rate constants for reaction of OH with CD₃COOH (acetic acid-d₃) and CD₃COOD (acetic acid-d₄) confirming that the dominant reaction mechanism is H-abstraction from the carboxylic group.
DE: 0399 General or miscellaneous
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005