A compound is said to be aromatic, if it obeys the following rules:
- The molecule must be cyclic.
- The molecule must be co-planar.
- Complete delocalisation of it-electrons in the ring.
- Presence of (4n + 2) π electrons in the ring where n is an integer (n = 0,1,2 …)
This is known as Huckel’s rule.
Example:
1. It is cyclic one.
2. It is a co-planar molecule.
3. It has six delocalised ir electrons.
4. 4n + 2 = 6
4n = 6 – 2
4n = 4
n = 1
It obey Huckel’s rule, with n = 1, hence benzene is aromatic in nature
