Question

Which of the following are aromatic compounds?

• A. Only (i) and (ii)
• B. Only (ii) and (iii)
• C. Only (i) and (iii)
• D. All are aromatic

Answer 1

The Correct Option is B

To determine which of the given compounds are aromatic, we need to apply Huckel's rule and other conditions for aromaticity:

A compound is considered aromatic if it satisfies the following criteria:

• It must be cyclic.
• It must be planar, allowing for the delocalization of electrons.
• It must be fully conjugated, meaning every atom in the ring has a p-orbital.
• It must follow Huckel's rule, which states that it must have 4n + 2 π electrons, where n is a non-negative integer.

1. Compound (i): This compound is bicyclic and does not have continuous conjugation throughout the ring. It fails to satisfy the requirement of being fully conjugated, hence it is non-aromatic.
2. Compound (ii): Known as pyrrole, this compound is cyclic, planar, and has 6 π electrons (4 from the double bonds and 2 from the nitrogen lone pair). It satisfies the 4n + 2 rule with n=1. Thus, it is aromatic.
3. Compound (iii): Known as pyridine, this compound is also cyclic, planar, and has 6 π electrons (2 from each double bond, making it meet the 4n + 2 rule with n=1). Thus, it is aromatic.

Based on the analysis, only compounds (ii) and (iii) are aromatic, and the correct answer is:

Only (ii) and (iii)