8 Oxidation of Aromatics (Carstensen and Dean, IJCK 2012)(Lin and Lin, JPC 1986)(Zhou, Kislov, Mebel, JPC A 2012)Oxyradicals are likely key intermediatesGenerally we look at the oxidation of benzene. It forms an oxyradical which decomposes to form a 5-member ring and CO.How does that translate to a larger PAH?We have been examining the decomposition.
9 Computational Details Quantum chemistry calculationsDFT - B3LYP/6-311G(d,p)Reaction kineticsK, atm using MultiWellComparison to experimentsFrank et al. (1994)1.3 – 2.5 atmLin and Lin (1986)0.4 – 0.9 atmComputational results: You, Zubarev, Lester, Frenklach, JPC A 2011
10 B3LYP, M05-2X and M06-2X 1 atm + CO + CO Basis set: 6-311G(d,p) (0) 47.8(45.4)[43.2]36.5(34.7)[33.0]24.7(22.9)[21.9]+ CO(0)50.8(50.5)[49.3]55.3(54.6)[52.3]39.7(38.6)[36.5]70.2(73.4)[69.2]63.0(67.6)[63.3]73.8(77.3)[74.9]B3LYP:(M05-2X):[M06-2X]:Basis set: 6-311G(d,p)
11 Multiwell -Argon was the bath gas collider 0.00010.000210-3-2-1Species FractionTime (sec)50001000015000200002500030000350004000045000Average Vibrational Energy (cm)Solves time-dependent 1-D energy transfer master equationsSolved stochastically using the Gillespie algorithmaverage vibrational energy of reactantkT,P= slopekT,P-technique explained well by David Golden-Argon was the bath gas collider
12 EdownEdown = 260 cm-1Edown = cm-1Lin and Lin (1986)Temperature dependent Edown expression from Hippler, Troe, Wendelken, JCP 1983.
26 Decomposition Rate 10 atm 1 atm 0.1 atm 0.01 atm 10 atm 10 atm 1 atm -Make sure to emphasizes that the pressure dependence is new. Not seen in past.1 atm1 atm0.1 atm0.1 atm0.01 atm0.01 atm
27 Armchair Decomposition “Free Edges”2 Free EdgeFree EdgeNon-Free Edge1 Free Edge1 atmAsk question about blue line.1 Free Edgekcal/mol
28 Substrate Size 1 atm -Affect is larger then expected -More work needs to be done in understand the assumption from molecular to edge reaction.
29 Zigzag vs Armchair 1 atm ZZ I ZZ II AC II AC I ZZ I ZZ II AC II AC I Armchair IZZ IZZ IIAC IIAC I1 atmArmchair IIZZ IZZ IIAC IIAC IZigzag I-emphasize two things. Zigzag and armchair are the same. All at same time and same order of magnitudeZigzag II
31 Kinetics Correlation with HOMA? HOMAoxyradical ringkT = 2000 K, P = ∞ (s-1)Barrier height (kcal/mol)
32 > >> Conclusions Proliferation of zigzag-edges in flames The decomposition of oxyradicals:temperature, pressure, substrate-size, site dependentarmchair rates are close to those of a zigzag-edgecorrelated with aromaticityThe following generalization can be made:2 free edgesfree edge1 free edgefree edgeno free edges>>>Proliferation of zigzag-edges in flames
33 Acknowledgements DOE-BES Prof. William A. Lester, Jr. Dr. Dmitry Zubarev (moving to Harvard U.)Dr. Russell Whitesides (now at LLNL)Prof. Xiaoqing You (now at Tsinghua U.)David Edwards
Your consent to our cookies if you continue to use this website.