Unimolecular decomposition of the n-C3H7 radical. Direct dynamics calculation of the thermal rate constant

Abstract

Rate constants for the unimolecular decomposition of the n-propyl radical have been calculated over the temperature range 250–2600 K, using variational transition state theory (VTST) with rectilinear coordinates and transmission coefficients calculated by the zero-curvature (ZCT) and small-curvature (SCT) tunneling approximations. Single-level calculations, based upon AM1 potential energy surfaces using AM1 parameters optimized on the basis of high level ab initio calculations (UMP2/6-311++G**) for this reaction, yield rate constants in good agreement with experiment. Dual-level direct dynamics calculations which explicitly include the results of the ab initio calculations, yield rate constants within a factor of 2 of the experimental data. Results of using the new AM1 parameters for the decomposition of n-C₅H₁₁ are encouraging.