OH formation in the reaction of acetyl radical with O2: Ab initio and RRKM reaction mechanism study

PHYS 460

Andrea Maranzana, amaranza@umich.edu, Atmospheric, Oceanic, and Space Sciences & Chemistry Dept, University of Michigan, 1218 Space Research Building, 2455 Hayward Street, Ann Arbor, MI 48109, Glauco Tonachini, glauco.tonachini@unito.it, Dipartimento di Chimica Generale ed Organica Applicata, University of Torino, Corso Massimo D'Azeglio 48, Torino, 10125, Italy, and John R. Barker, jrbarker@umich.edu, Department of Atmospheric, Oceanic, and Space Sciences, Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-2143.
The acetyl radical plays an important role in tropospheric, photochemical and pyrolysis processes. Under tropospheric conditions, it reacts with oxygen to produce mainly the acetylperoxy radical (precursor of peroxyacetylnitrate), but also a small amount of OH radicals. The OH yield shows a strong pressure dependency. Since the reaction mechanism initiated by acetyl +O2 is very complex and the exact mode of formation of OH is still uncertain, we have investigated by ab-initio methods all the potential intermediates and transition structures leading to OH formation. Based on this potential energy surface,we have carried out multi-channel, multi-well RRKM calculations for atmospheric conditions. We have used a novel pseudo-first order microcanonical method to incorporate competing bimolecular reactions in the unimolecular reaction system. OH yields obtained with different colliders in presence of various amounts of O2, are reported. The results are in good agreement with available experimental data.

Poster Session
7:30 PM-10:00 PM, Wednesday, 13 September 2006 Moscone Center -- Hall D, Poster

8:00 PM-10:00 PM, Monday, 11 September 2006 Moscone Center -- Hall D, Sci-Mix

Division of Physical Chemistry

The 232nd ACS National Meeting, San Francisco, CA, September 10-14, 2006