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Feng Zhang, Theodore S. Dibble

Impact of tunneling on H-migration of n-propylperoxy radical. Feng Zhang, Theodore S. Dibble. Chemistry Department, State University of New York College of Environmental Science and Forestry (SUNY-ESF). ICCK, MIT, 07/10/2011-07/14/2011. tunneling. H-migration. HO 2 elimination.

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Feng Zhang, Theodore S. Dibble

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  1. Impact of tunneling on H-migration of n-propylperoxy radical Feng Zhang, Theodore S. Dibble Chemistry Department, State University of New York College of Environmental Science and Forestry (SUNY-ESF) ICCK, MIT, 07/10/2011-07/14/2011

  2. tunneling H-migration HO2 elimination Scheme of alkane auto-ignition (<1000 K) (or ▪H, O)

  3. Goals Tunneling treatment in literature: 1D model (Wigner or Eckart) Use multidimensional treatment to get tunneling right; Give guidance on 1D tunneling models for peroxy radicals.

  4. Tunneling treatments V1 V0

  5. Methodologies 1. Ab initio calculations Benchmark: CCSD(T)/maug-cc-pVTZ//M052X/6-311+G(2df,2p) 2. Tunneling treatment and rate constant calculation VaG requires vibrational analysis along the whole path! Select DFT method based on the benchmark Calculate rate constants with multidimensional tunneling

  6. 1,5 H-migraion: M052X/MG3S 1,4 H-migration: B3LYP/MG3S HO2 elimination: B1B95/MG3S Select DFT and basis set with least error MG3S=6-311+g(2df,2p) for C,H, O 1,5 H-migration

  7. The “lucky” benchmark a From Prof. Allen’s talk this morning!

  8. Reaction paths TS-15 (1836 cm-1) TS-14 (2172 cm-1) TS-e (1027 cm-1)

  9. Multidimensional tunneling coefficients R1 R2 R3 R2 R1 R3

  10. Comparison of tunneling treatments for 1,4 H-migration

  11. Comparison of tunneling treatments for 1,5 H-migration

  12. Rate constants in the high pressure limit SRG: J. Phys. Chem. A 114, 5689, 2010 HCD:J. Phys. Chem. A 114, 6594, 2010

  13. Summary High pressure limiting rate constants were computed for H-migration, HO2 elimination of n-propyl peroxy radical. First multidimensional tunneling treatment of these reactions in alkyl peroxy radical Wigner’s formula largely underestimates tunneling. Eckart potential gives reasonable predictions.

  14. Acknowledgements Prof. Donald G. Truhlar, Dr. Jingjing Zheng U.S. Department of Energy Thanks for your attention!

  15. Internal rotation in CH3CH2CH2OO▪ Reactant TS-14s TS-15s TS-e

  16. Hindered rotor treatment Torsion Eigenvalue Summation(TES) method Potential Energy(cm-1)

  17. Pressure dependence of Eckart tunneling coefficient logΓ 1atm

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