Abstract The σ-orbital manifold of cubane 1, as suggested by its PE spectrum, is divided into two sets separated by a 3 eV gap extending from∼-10.5 eV to∼-13.5 eV. Halogen substituents with np AO basis energies falling into this gap (eg Cl or Br) will, therefore, hyperconjugate appreciably with both sets. Interaction with the lower-lying set will lead to the usual destabilization ('normal'hyperconjugation), whereas interaction with the set above ...
