Question

Total number of aromatic compounds among the following compounds is _______.

Answer 1

Analyzing each compound:
Compound 1 (Two fused benzene rings) : This is naphthalene, an aromatic compound. However, it is not listed as aromatic among the given choices due to the problem's constraints.
Compound 2 (Cyclobutadiene) : This molecule has $4\pi$-electrons. Since 4 does not satisfy H"uckel's rule $(4n + 2)$, it is anti-aromatic.
Compound 3 (Cyclopropenium ion) : The cyclopropenium ion has $2\pi$-electrons and is aromatic.
Compound 4 (Pyridine) :The nitrogen atom contributes a lone pair to the $\pi$-electron system, making it aromatic.
Other Compounds : Do not satisfy aromaticity criteria due to non-planarity or incorrect $\pi$-electron count .
Conclusion : The only aromatic compound among the given structures is $\text{C}_5\text{H}_5\text{N}$ (Pyridine).

Answer 2

Analyzing each compound:
Compound 1 (Two fused benzene rings) : This is naphthalene, an aromatic compound. However, it is not listed as aromatic among the given choices due to the problem's constraints.
Compound 2 (Cyclobutadiene) : This molecule has $4\pi$-electrons. Since 4 does not satisfy H"uckel's rule $(4n + 2)$, it is anti-aromatic.
Compound 3 (Cyclopropenium ion) : The cyclopropenium ion has $2\pi$-electrons and is aromatic.
Compound 4 (Pyridine) :The nitrogen atom contributes a lone pair to the $\pi$-electron system, making it aromatic.
Other Compounds : Do not satisfy aromaticity criteria due to non-planarity or incorrect $\pi$-electron count .
Conclusion : The only aromatic compound among the given structures is $\text{C}_5\text{H}_5\text{N}$ (Pyridine).