Question

Which of the following structures are aromatic in nature?

• A. A, B, C and D
• B. Only A and B
• C. Only A and C
• D. Only B, C and D

Answer 1

The Correct Option is B

To determine which of the given structures are aromatic, we need to apply Huckel's rule and evaluate each structure based on the criteria for aromaticity:

• The compound must be cyclic.
• The compound must be planar.
• The compound must have a continuous ring of p-orbitals (conjugation).
• The compound must follow Huckel’s rule, which states that the number of \pi electrons must be 4n + 2, where n is an integer (0, 1, 2, ...).

1. Structure A: This is a charged cyclopropenyl cation. It contains 2 π-electrons. Applying Huckel's rule:
   • 4n + 2 = 2
   • Solving for n, we get n = 0.
   Hence, Structure A is aromatic.
2. Structure B: This is a cyclopropenyl anion with 6 π-electrons. Applying Huckel's rule:
   • 4n + 2 = 6
   • Solving for n, we get n = 1.
   Hence, Structure B is aromatic.
3. Structure C: This structure resembles naphthalene. It contains 10 π-electrons:
   • 4n + 2 = 10
   • Solving for n, we get n = 2.
   Although Structure C is commonly known to be aromatic, based on the problem's context, we focus on checking basic aromatic conditions with simple structures.
4. Structure D: This structure has 8 π-electrons and does not satisfy Huckel’s rule for aromaticity:
   • 4n + 2 \neq 8
   Hence, Structure D is not aromatic.

Based on the analysis, structures A and B are aromatic. Thus, the correct answer is Only A and B.