Tunneling effect in 1,5 H-migration of a prototypical OOQOOH

Highlights: • Multidimensional tunneling calculations are carried for 1,5 H-migration in OOCH₂CH₂CH₂OOH. • Small curvature tunneling dominates large curvature tunneling, even at the lowest energies. • The tunneling correction is as high as a factor of 2 at temperatures relevant to diesel auto-ignition. Propane is the smallest molecule that can serve as a model of the chemistry of diesel autoignition. Diesel autoignition requires H-migration reactions of the type OOCH₂CH₂CH₂OOH → HOOCH₂CH₂CHOOH. Previous studies of this type of H-migration reaction accounted for tunneling (through-barrier processes) using 1-D models of the reaction coordinate, namely, the Eckart or Wigner approximations. Here we present the first study to use multi-dimensional approaches, specifically, small- and large-curvature tunneling, to treat through-barrier processes. Calculations are carried out using the Polyrate program and make use of the M05-2X/6-31+G(d,p) level of theory.