Aromaticity
Aromaticity is a property of cyclic, planar molecules with delocalised π‑electrons that gives exceptional stability.
Aromaticity
Aromatic compounds are cyclic, planar molecules with a ring of resonance bonds that are more stable than a comparable non‑aromatic structure.
Hückel's Rule
For a molecule to be aromatic, it must have 4n + 2 π‑electrons (where n = 0, 1, 2, …).
| n | Electrons | Example |
|---|---|---|
| 0 | 2 | Cyclopropenium cation |
| 1 | 6 | Benzene |
| 2 | 10 | Naphthalene |
Criteria for Aromaticity
- Cyclic — atoms form a ring
- Planar — all atoms in the same plane
- Conjugated — alternating single and double bonds
- 4n + 2 π‑electrons — satisfies Hückel's rule
Benzene
Benzene (C₆H₆) is the classic aromatic compound. Its six π‑electrons are delocalised over the six carbon atoms, giving each C–C bond a bond order of 1.5. This delocalisation makes benzene much less reactive than expected for a molecule with three double bonds.
Related molecules: Benzene
Learn more: Organic Chemistry