Temperature- and pressure-dependent kinetics studies of gas phase reactions of atomic chlorine with a series of ketones

PHYS 18

Zhijun Zhao, gtg661u@mail.gatech.edu1, Dow Huskey, dhuskey3@gatech.edu2, J. M. Nicovich, mike.nicovich@chemistry.gatech.edu2, Michael L. McKee, mckee@chem.auburn.edu3, and Paul H. Wine, paul.wine@chemistry.gatech.edu4. (1) School of Earth & Atmospheric Sciences, Georgia Institute of Technology, 311 Ferst Dr. NW, Atlanta, GA 30332-0340, (2) School of Chemistry & Biochemistry, Georgia Institute of Technology, 901 Atlantic Drive NW, Atlanta, GA 30332-0400, (3) Department of Chemistry and Biochemistry, Auburn University, Auburn, AL 36849, (4) Schools of Chemistry & Biochemistry and Earth & Atmospheric Sciences, Georgia Institute of Technology, 901 Atlantic Drive NW, Atlanta, GA 30332-0400
Atomic chlorine is an important initiator of the atmospheric degradation of many oxygenated organic compounds, including ketones, particularly in marine environments. We have coupled laser flash photolysis of Cl2CO/ketone/N2 mixtures with time-resolved detection of Cl by atomic resonance fluorescence spectroscopy to investigate the kinetics of Cl reactions with acetone (R1), 2-butanone (R2), 3-pentanone (R3), and methylvinyl ketone (R4). R1, R2, and R3 proceed via H-transfer pathways. Observed temperature dependences of k1 – k3 are significantly different from those reported in the literature. R4 proceeds primarily by Cl addition to the double bond and, therefore, displays both temperature and pressure-dependent kinetics. Reversible adduct formation is observed at T ~ 425 K which, in conjunction with electronic structure calculations, allows the C–Cl bond strength in the product haloalkyl radical to be evaluated. Higher temperature studies aimed at characterizing the kinetics of H-transfer pathways for R4 are in progress and will be reported.
 

Physical Chemistry of Atmospheric Processes
8:00 AM-12:00 PM, Sunday, April 6, 2008 Morial Convention Center -- Rm. 343, Oral

Division of Physical Chemistry

The 235th ACS National Meeting, New Orleans, LA, April 6-10, 2008