Theoretical Study of the Allyl Radical: Structure and Vibrational Analysis

The electronic structure of the allyl radical CH₂CHCH₂ and its vibrational spectrum have been calculated from ab initio multiconfiguration Hartree-Fock (MCHF) wave functions. While the Hartree-Fock (HF) model incorrectly predicts a nonsymmetric structure, the MCHF calculations indicate that the allyl radical has C_2ν symmetry in accord with ESR evidence. Harmonic vibrational frequencies of all the normal modes are reported for the allyl radical and various deuterium-substituted analogues. Most noteworthy are the out-of-plane bending mode frequencies calculated at 760-790 cm^-1 which are predicted to give rise to a very intense and characteristic band of the allyl radical.