Radical hydrogen transfer reactions: benchmark calculations on the C2H4…H…C2H4 transition state

High level ab initio calculations using coupled-cluster (CC) methods have been applied to calculate the barrier height of the prototypical hydrocarbon radical hydrogen transfer reaction between C2H4 and C2H5. The barrier at 298 K is estimated to be 27.7–30.7 kcal mol−1. Second-order perturbation theory based on a restricted open-shell Hartree-Fock reference, unlike spin contaminated UHF-MBPT(2), provides reasonable agreement with the CC calculations, and may be of use in studies of the RHT reaction of larger systems.