JEE Chemistry 2025 Question with Solution

Given: Compounds (a) to (h) are to be classified as aromatic or not aromatic.

Find: Which set of compounds is aromatic.

Use Huckel's rule for aromaticity:

• cyclic molecule
• planar molecule
• fully conjugated $\pi$ system
• contains $(4n+2)$ $\pi$ electrons

A compound that fails planarity or full conjugation is not aromatic. A cyclic, planar, fully conjugated compound with $4n$ $\pi$ electrons is also taken here as not aromatic.

From the given solution:

• (a) cyclic, planar, conjugated with $6\pi$ electrons, so it is aromatic.
• (b) has $4\pi$ electrons, so it is not aromatic.
• (c) cyclic, planar, conjugated with $6\pi$ electrons, so it is aromatic.
• (d) cyclic, planar, conjugated with $6\pi$ electrons, so it is aromatic.
• (e) cyclic, planar, conjugated with $6\pi$ electrons, so it is aromatic.
• (f) is not planar, so it is not aromatic.
• (g) has $4\pi$ electrons, so it is not aromatic.
• (h) cyclic, planar, conjugated with $6\pi$ electrons according to the keyed result, so it is aromatic.

Therefore, the aromatic compounds are (a), (c), (d), (e), (h) and the not aromatic compounds are (b), (f), (g).

The correct option is D.

Given: The structures (a) to (h) shown in the figure.

Find: Which option correctly designates them as aromatic or not aromatic.

To determine aromaticity, check these conditions one by one:

1. The molecule must be cyclic.
2. The molecule must be planar.
3. The molecule must be fully conjugated.
4. The molecule must contain $(4n+2)$ $\pi$ electrons.

The extracted solution states:

(a) Aromatic. It is cyclic, planar, conjugated, and has $6\pi$ electrons.

(b) Not aromatic. It has $4\pi$ electrons, so it does not satisfy Huckel's rule for aromaticity in this question's classification.

(c) Aromatic. It is cyclic, planar, conjugated, and has $6\pi$ electrons.

(d) Aromatic. It is cyclic, planar, conjugated, and has $6\pi$ electrons.

(e) Aromatic. It is cyclic, planar, conjugated, and has $6\pi$ electrons.

(f) Not aromatic. Its structure is not planar, so effective cyclic conjugation is prevented.

(g) Not aromatic. It has $4\pi$ electrons.

(h) Aromatic. It is classified in the provided solution under aromatic compounds.

Hence the final grouping is:

• Aromatic: (a), (c), (d), (e), (h)​​
• Not aromatic: (b), (f), (g)

Therefore, the correct option is D.