1. Aromatic character of compounds
According to Huckel's rule, a compound is aromatic if it is
• Cyclic
• Planar
• Conjugated
• Has (4n + 2) π electrons, n = 0, 1, 2, 3, ……
2. Antiaromatic compounds
Planar conjugated cyclic systems containing 4nπ electrons (n = 1, 2, 3, …..)
3. Non aromatic systems
Some antiaromatic compounds adopt non planar geometries to become stable. They have 4π electrons but are non planar.
