In the following models, the sp2 carbon atoms are dark gray and the hydrogens are cyan. The contributing p-orbitals in the display are colored spheres above and below the plane of the sigma bonds. The different phases of these orbitals are colored blue and red, and are separated by nodal surfaces at which electron density is zero. Π-orbitals are formed by overlap of p-orbitals having like phases. The lowest energy π-orbital, π1, has a single nodal plane, that of the atoms of the ring. Higher energy π-orbitals may be viewed by clicking appropriate buttons under the display. An increasing number of nodes parallels the increase in energy. In two of the orbitals, a node passes through two carbon atoms, so the π electron density at those sites is zero. The three lowest energy π-orbitals, π1, π2 & π3 are bonding. The three higher energy orbitals, π4*, π5* & π6* are antibonding. The molecules can be rotated by clicking on the structure and dragging the mouse. Holding the shift key during this operation allows zooming.
In the following models, sp2 carbon atoms are dark gray and hydrogens are cyan. The p-orbitals are represented by colored spheres above and below the plane of the sigma bonds. The different phases of the p-orbitals are colored blue and red. Regions in which adjacent orbitals undergo a phase change are called nodes. Orbital electron density is zero in such regions. Π-orbitals are formed by overlap of p-orbitals having like phases. The lowest energy π-orbital, π1, has a single nodal plane, that of the atoms of the ring. Higher energy π-orbitals may be viewed by clicking appropriate buttons under the display. An increasing number of nodes parallels the increase in energy. The three lowest energy π-orbitals are bonding. The three higher energy orbitals are antibonding. The HOMO is π3; the LUMO is π4*. The models can be rotated by clicking on the structure and dragging the mouse. Holding the shift key during this operation allows zooming.