Theoretical study of cyclopropane and cyclopropyl radical: Structure and vibrational analysis

Ab initio Hartree-Fock calculations of the structure and vibrational frequencies of cyclopropane and cyclopropyl radical are presented. It is found that the αCH bond in the radical is bent 39.3° out of the CCC plane, the inversion barrier is 3.0 kcal/mol and the pyramidal bending mode has a frequency of 713 cm^-1. Compared to cyclopropane, the αCC bonds are stronger, and the βCC bond is weaker in the radical. The shortening of the áCH bond, and the hyperconjugative interaction of the unpaired electron onto the βCH bonds previously observed in alkyl radicals, are found to be much less pronounced in the cyclopropyl radical.