Weblink 15.7 The π MOs of benzene and butadiene

In benzene MO1, MO2 and MO3 are occupied (MO2 and MO3 are degenerate).

In cyclobutadiene with a square geometry, MO1 is doubly occupied and there is one electron each in the degenerate orbitals MO2 and MO3.

In cyclobutadiene with a rectangular geometry, MO1 and MO2 are both doubly occupied. MO2 and MO3 are no longer degenerate.

• Click and drag to rotate the structure; hold down shift, then click and drag to zoom.
• Select the MO to view using the menu.
• Select the type of surface using the radio buttons.
• Use the check box to display the nodal surface (zero contour - shown as a green mesh).
• Use the buttons to change the iso-surface value.