Ab initio direct dynamics study of cyclopropyl radical ring-opening.

Quasiclassical direct dynamics simulations, at the CASSCF(3,3)/6-31G(d) level of theory, are used to study the stereochemistry of the electrocyclic ring-opening reaction of the cyclopropyl radical. The trajectories are initiated at the reaction's transition state (TS), with their initial conditions sampled from the TS's 174 degrees C Boltzmann distribution. Intrinsic reaction coordinate calculations predict the overall reaction to have disrotatory stereochemistry. Though this is the preferred initial reaction stereochemistry in the trajectories, 43% of the trajectories follow the conrotatory path. Four unique trajectory types are observed during 200 fs dynamics of the product allyl radical. Intramolecular vibrational energy redistribution and internal rotation are incomplete on this time scale, and a statistical distribution of the allyl isomers is not observed.