Question

Which of the following is not an aromatic compound? 

• A. 1
• B. 2
• C. 3
• D. 4

Hint:

To test aromaticity, check the number of pi electrons in a cyclic compound. It must follow Hückel's rule: \(4n + 2\) pi electrons.

Answer 1

The Correct Option is D

Aromatic compounds follow the rules defined by Hückel's rule, which states that a compound is aromatic if it is cyclic, planar, and has a total of \(4n + 2\) delocalized pi electrons, where \(n\) is an integer. 

- Option (1) is a benzene ring (\(C_6H_6\)), which satisfies the criteria for aromaticity, as it has 6 pi electrons, a multiple of \(4n + 2\). 
- Option (2) is naphthalene, which is also aromatic as it has 10 pi electrons, satisfying Hückel's rule. 
- Option (3) is another aromatic compound, specifically a 5-membered ring with conjugated double bonds. 
- Option (4), however, is a non-aromatic compound. It does not satisfy the aromaticity condition because it lacks a fully conjugated system, making it non-aromatic.

Thus, the correct answer is: \[ \text{(4) is the non-aromatic compound.} \]