A separate window will open containing the model. The Bonding and Anti-bonding p Molecular Orbitals in Ethene and Cyclopropane Ethen and cyclopropane are classified as alkene and alkane respectively, but the latter is often regarded as having properties associated with the former. These orbitals show why. This interaction is favoured both by good overlap between these two orbitals and by minimising the energy difference between them. To see how this works in practice, the table below shows the quantitative form and energies of the LUMO orbitals of the electrophile.
Various points are noteworthy.
In contrast, the LUMO of iodomethane has an appropriate energy, but its shape has a higher density at the iodine end than the carbon end. Thus e.g. I - can attack at the iodine end under suitable circumstances. Finally, we note that whilst substitution at carbon electrophiles always goes with inversion, Silicon can substitute with retention of configuration, as the shape and energy of its LUMO in SiH 3 Fimplies. The result is written out into a 3D computer graphics file in 3DMF format, and displayed in a browser using a 3DMF plug-in.