Among $\boldsymbol{P}, \boldsymbol{Q}, \boldsymbol{R}$ and $\boldsymbol{S}$, the aromatic compound(s) is/are

(A) $\boldsymbol{P}$; (B) $\boldsymbol{Q}$; (C) $\boldsymbol{R}$; (D) $\boldsymbol{S}$

JEE Advanced · 2013 · 02 Jun 2013 · Paper 1 · General Organic Chemistry

Among

P, Q, R

and

S

, the aromatic compound(s) is/are

(A) $P$ ✓ Correct
(B) $Q$ ✓ Correct
(C) $R$ ✓ Correct
(D) $S$ ✓ Correct

Answer: (A), (B), (C), (D)

Solution

All four compounds are aromatic. For aromaticity, a compound must be cyclic, planar, fully conjugated, and follow Hückel's rule (4n+2 π electrons).

P: Cyclopentadienyl cation (4 π electrons, but with positive charge, follows 4n+2 rule) - aromatic
Q: Cyclopropenyl cation (2 π electrons, 4n+2 with n=0) - aromatic
R: Pyrrole anion (6 π electrons) - aromatic
S: Phenoxide ion (6 π electrons) - aromatic

All satisfy the criteria for aromaticity.

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JEE Advanced · 2013 · 02 Jun 2013 · Paper 1 · General Organic Chemistry

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