Electronic control of the stereochemistry of electrophilic and nucleophilic attack on double bonds in 6-membered rings

CNDO and ab initio MO calculations reveal a deformation of the π^* and π orbitals of cyclohexene in the axial directions, thus providing a reasonable explanation for the axial attack on cyclohexene either by electrophiles or by nucleophiles. It is shown in the case of 1-butene by an ab initio calculation that this orbital deformation is a result of the mixing of the π and σ orbitals of the double bond under the influence of the allylic C-C bond.