Benzene And Alkyl Benzene Result Question 10

10. Which of the following compounds is not aromatic?

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(2019 Main, 9 Jan II)

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Answer:

Correct Answer: 10. ( b )

Solution:

Aromaticity of a compound can be decided by Huckel’s rule. In cyclopentadienyl cation (b), resonance takes place as follows:

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Huckel’s rule as it has conjugated $4 \pi$-electron $(4 n \pi, n=1)$ system. Rest of the species are aromatic as each of them belongs to $6 \pi$-electron $[(4 n+2) \pi, n=1]$ system.