Question

Question: Which compounds are aromatic? For any compound that is not aromatic, state why this is so.

Short answer

Answer

a.

Not aromatic in nature

b.

Not an aromatic compound

c.

Non-aromatic compound

d.

Non-aromatic compound

Step-by-step solution

Aromatic compounds

The compounds which fulfil all of the following conditions are aromatic in nature:

• The compounds which are cyclic.
• The compounds which are planar.
• The compounds which are conjugated with $\left(4n+2\right)\mathrm{\pi }$electrons.

The compound which is aromatic in nature is always more stable than the corresponding acyclic compound with the same number of $\mathbf{\pi }$electrons.

The aromatic compounds among the given compounds

a. In the following compound, the marked carbon atoms are not $s{p}^2$hybridized. They are not completely conjugated. This compound is not aromatic.

Not aromatic in nature

b. The circled carbon atom is not $s{p}^2$hybridized. These are not completely conjugated. This compound is not aromatic in nature.

Not an aromatic compound

c. This compound has $12\mathrm{\pi }$electrons. It does not have $\left(4n+2\right)\mathrm{\pi }$electrons. Therefore, this compound is not aromatic in nature.

Non-aromatic compound

d. This compound has $12\mathrm{\pi }$electrons and is not aromatic. It does not have $\left(4n+2\right)\mathrm{\pi }$electrons.

Non-aromatic compound