Spatially projected generalized valence bond description of the π-states of allyl radical

Ab initio, spatially projected generalized valence bond [GVB(SP)] calculations are reported for the ground and (π-electron) excited states of allyl radical. We find that the wavefunctions of the ground and first excited state correspond closely to the classical valence bond description of resonant and anti-resonant states, [graphic]. The higher states involve excitation of Rydberg orbitals, but even here the orbitals of the GVB(SP) wavefunctions are basically localized. The theoretical value obtained for the allyl resonance energy is 14 kcal in good agreement with thermochemical estimates.