Rules for Aromaticity  (Huckel's Rule)

1. must be cyclic
2. must be planar
3. each atom of the ring must have a p orbital and these p orbitals
must be perpendicular to the plane of the ring
4. Must contain 4n+2 pi electrons (where n = 0, 1, 2, ...)






EXAMPLES

application of rule #1


this compound cannot be aromatic because it is not cyclic


application of rule #2 and 3


benzene is planar and each atom has a P orbital which is
perpendicular to the plane of the ring



this compound is not aromatic because one of the carbons
in the ring is saturated (and thus does not have a p orbital).


application of rule #4


this compound is not aromatic because it has 4 pi electrons.