Question

Which of the following are aromatic?

• A. B and D only
• B. A and C only
• C. A and B only
• D. C and D only

Answer 1

The Correct Option is A

To classify compounds as aromatic, the following criteria must be met:

1. Cyclic structure.
2. Planar geometry.
3. A continuous ring of p-orbitals (fully conjugated system).
4. Adherence to Huckel's rule: the number of π-electrons must equal \(4n + 2\), where \(n\) is a non-negative integer.

Analysis of each compound:

1. Compound A (Naphthalene): Cyclic, planar, fully conjugated, and possesses 10 π-electrons. This aligns with Huckel's rule (\(4n + 2 = 10\), \(n = 2\)). Conclusion: Aromatic.
2. Compound B (Benzene): Cyclic, planar, fully conjugated, and contains 6 π-electrons. This satisfies Huckel's rule (\(4n + 2 = 6\), \(n = 1\)). Conclusion: Aromatic.
3. Compound C: Lacks planarity due to steric hindrance, which disrupts the tubular structure. Conclusion: Not aromatic.
4. Compound D (Anthracene): Cyclic, planar, fully conjugated, and has 14 π-electrons. This conforms to Huckel's rule (\(4n + 2 = 14\), \(n = 3\)). Conclusion: Aromatic.

Based on this evaluation, compounds B and D are aromatic as they satisfy all required conditions.

The correct designation is: B and D only