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