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Complete Guide to Understanding And Drawing Frost Circle

Frost Circle

Frost circle is a method to construct pi molecular orbital diagrams for planar and conjugated rings.

How to draw Frost circles?

  1. Draw a circle

  2. Inscribe the shape of the molecule into the circle making sure that one of the vertices hits the bottom of the circle.

  3. Put a horizontal line through the center of the circle.

  4. Put a dash in each place where the vertices hit the circle. Dashes represent molecular orbitals. Those below the horizontal lines are bonding. Orbital on the horizontal lines are nonbonding and orbitals above the horizontal line are antibonding.

  5. Distribute the pi electrons from the bottom up.

Frost Circle For Cyclobutadiene

Frost Circle For Cyclobutadiene
Frost Circle For Cyclobutadiene

We can see that cyclobutadiene has two electrons in nonbonding orbitals which makes it unstable and not aromatic.

For a molecule to be aromatic, all of its electrons will be in the bonding orbitals.



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