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

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

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 V0V0 V1V1

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

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

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. R3 Multidimensional tunneling coefficients R1 R2 R1 R2 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, HO 2 elimination of n-propyl peroxy radical. Wigner’s formula largely underestimates tunneling. Eckart potential gives reasonable predictions. First multidimensional tunneling treatment of these reactions in alkyl peroxy radical

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

15. Internal rotation in CH 3 CH 2 CH 2 OO ▪ Reactant TS-15s TS-14s TS-e

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

17. logΓ Pressure dependence of Eckart tunneling coefficient 1atm