Chapter 14, Problem 14.7YT

Interpretation Introduction

Interpretation:

It is to be shown how many nodal planes are perpendicular to the bonding axes in ${\text{π}}_{\text{6}}{}^{\text{*}}$ MO of benzene from the given figure.

Concept introduction:

The MO arises from interacting p AOs of two atoms. MO energies differ as a result of constructive and destructive interference among contributing AOs. Each pair of overlapping AOs with the same phase lowers the MO energy and corresponds to a bonding interaction in an MO while each pair of overlapping AOs with the opposite phases raises the MO energy and corresponds to an antibonding interaction in an MO. The destructive interference gives rise to a nodal plane. The contributions of the AOs to produce a bonding, nonbonding or antibonding MO depend on the net interaction.  In the MO diagram, only $\text{π}$ electrons are considered. In the case of a conjugated system, the number of $\text{π}$ electrons corresponds to p orbitals, which are considered atomic orbitals (AOs) in the MO diagram. For conjugated alkene, there are also equal numbers of bonding and antibonding orbitals. The bonding interaction results from adjacent p orbitals, which are in the same phase, and when the adjacent orbital in the opposite phase results in antibonding interaction, which is also represented by a nodal plane.