The kinetics of unimolecular reactions of 1-propyl peroxy radical (1,5 and 1,4 H-transfer) were studied with multidimensional tunneling. Our results are the first accurate tunneling treatments of H-transfer reactions for peroxy radicals, which are key to the autoignition of diesel fuel. Small curvature tunneling (SCT) dominates, and the tunneling corrections ?(T) (in the high pressure limit) are significantly larger than those computed by the Wigner approach, but only slightly larger than those obtained with the asymmetric Eckart method. Tunneling is in much more important in the fall-off region, where the high-energy tail of the Boltzmann distribution is depleted, than in the high pressure limit. The accuracy of tunneling calculations in the fall-off region depends on the microcanonical tunneling coefficients, G(E). We find large differences in G(E) between the SCT and Eckart approaches, implying that Eckart tunneling can be very inaccurate for computing tunneling effects on k(P,T).

Tunneling in unimolecular H-shift reactions of a prototypical peroxy radical: 1-Propyl peroxy

243rd National Meeting (2012)

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