Atmos. Chem. Phys. Discuss., 10, 16747-16773, 2010
© Author(s) 2010. This work is distributed
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Does acetone react with HO2 in the upper-troposphere?
T. J. Dillon1, A. Pozzer2, J. N. Crowley1, and J. Lelieveld1,2
1Max-Planck-Institute für Chemie, Atmospheric Chemistry Division, Mainz, Germany
2EEWRC, Cyprus Institute, Nicosia, Cyprus

Abstract. Recent theoretical calculations showed that reaction of HO2 with acetone (CH3C(O)CH3) could be a potentially important sink for acetone and source for acetic acid in cold parts of the atmosphere (e.g. the tropopause region). The reaction HO2+CH3C(O)CH3⇌(CH3)2C(OH)OO (R1, R-1) was therefore studied experimentally at low-temperatures for the first time. HO2 was generated by pulsed laser photolysis, and converted by reaction with NO to OH for detection by laser induced fluorescence. Reduced yields of OH at T<220 K provided evidence for stabilisation of (CH3)2C(OH)OO at such temperatures. In contrast, no evidence for (R1) was observed at T>230 K, probably due to rapid thermal dissociation of the peroxy radical product back to reactants (R-1). The experimental data indicate that the rate coefficient for the forward reaction, k1(207 K), is larger than 1.6×10-12 cm3 molecule−1 s−1, in line with recent quantum mechanical calculations. In contrast, an upper limit for the equilibrium constant K1(T)=k1(T)/k-1(T) of 7.8×1028exp(50.6 kJ mol-1/RT) was obtained, considerably smaller than calculated from theory. Incorporation of these results into a global 3-D chemical model demonstrated that (R1) is neither a significant loss process for CH3C(O)CH3 nor a significant source of acetic acid in the atmosphere.

Citation: Dillon, T. J., Pozzer, A., Crowley, J. N., and Lelieveld, J.: Does acetone react with HO2 in the upper-troposphere?, Atmos. Chem. Phys. Discuss., 10, 16747-16773, doi:10.5194/acpd-10-16747-2010, 2010.
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