# Concept of Aromaticity

Aromaticity of compounds is based on certain rules. According to Huckel's rule, the number of pi electrons present should be a number denoted by the formula 4n + 2, where n is 0, 1, 2, 3, . . .. Hence, for compounds to be considered aromatic the number of pi electrons should be 2, 6, 10, . . .. In addition, the structure should also have a cyclic pi system to be aromatic. Atoms in the ring must have unhybridized

Test whether you can recognize the aromaticity of the structures in the examples that follow:

*p*orbitals. These unhybridized*p*orbitals must overlap resulting in a cyclic pi system. For this overlap, the structure must have planar (or nearly planar) configuration. In other words, the atoms related or involved in the pi bond should be in the same plane.Test whether you can recognize the aromaticity of the structures in the examples that follow:

**Tips for testing aromaticity**

Step 1 â€“ Count the number of pi electrons.

Step 2 â€“ See whether there is a cyclic *p* orbital overlap.

Predict the aromaticity of the compounds given below:

**Compound 1**

Number of pi electrons â€“ 6

Cyclic overlap of *p* orbitals â€“ Yes

Aromatic â€“ Yes

**Compound 2**

Number of pi electrons â€“ 4

Cyclic overlap of *p* orbitals â€“ No

Aromatic â€“ No

**Compound 3**

Number of pi electrons â€“ 6

Cyclic overlap of *p* orbitals â€“ Yes

Aromatic â€“ Yes

**Some examples of heterocyclic aromatic compounds.**