PHYS 600 |
| Chemically accurate ab initio Gaussian-3-type calculations of various rearrangements on the C10H9 and C10H11 potential energy surfaces (PES) have been performed to investigate formation mechanisms of naphthalene and indene originated from recombination of two cyclopentadienyl radicals (c-C5H5) as well as from intermolecular addition of cyclopentadienyl to cyclopentadiene (c-C5H6) at conditions relevant to combustion and pyrolysis. Utilizing the ab initio data, statistical theory calculations have been applied to obtain high-pressure limit thermal rate constants within the 300-3000 K temperature range, followed by calculations of relative product yields. For the C10H9 potential, rearrangements of 9-H-fulvalenyl radical (C5H5-C5H4) lead to the formation of naphthalene, fulvalene, and azulene with relative product yields depending on temperature. At low temperatures (T < 1000 K), naphthalene is predicted to be the major product (>50%), whereas at higher temperatures the naphthalene yield rapidly decreases and the formation of fulvalene becomes dominant. At T > 1500 K, naphthalene and azulene are only minor products accounting for less than 10% of the total yield. The high yields of fulvalene at higher temperatures indicate that reactions involving cyclopentadienyl radical and cyclopentadiene may contribute to the production of cyclopentafused PAH, which are supposed to be precursors of fullerenes. For rearrangements occurring on the C10H11 potential, a total of twelve reaction pathways have been mapped out producing indene and several azulene precursors: 1,5-, 1,7-, 1,8a-, and 1,3a-dihydroazulene. At temperatures relevant to combustion, the indene has been found as the major reaction product (>50%) followed by 1,5-dihydroazulene (25-35%), whereas all other products demonstrate only minor yields. The results of our computations for both C10H9 and C10H11 PESs have been combined to draw the detailed picture of radical-promoted reaction mechanisms leading from c-C5 species to the production of indene, naphthalene, azulene, and fulvalene in combustion flames. |
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PHYS Poster Session - Computational Spectroscopy and Reaction Dynamics
7:30 PM-10:00 PM, Wednesday, April 9, 2008 Morial Convention Center -- Hall A, Poster
Division of Physical Chemistry |