See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Aromaticity Analysis **Hückel's Rule & Aromatic Criteria:** For a compound to be aromatic, it must satisfy: - Cyclic structure - Planar geometry - Continuous conjugation - $(4n+2)$ π electrons (where $n = 0, 1, 2, ...$) **Evaluating each option:** **(A) Pyrrole ($C_4H_5N$):** - 5-membered ring with N lone pair contributing to conjugation - Total π electrons: 4 (from double bonds) + 2 (from N) = **6 electrons** ✓ Aromatic - N-H is NOT aromatic; the lone pair is part of the aromatic system **(B) Thiophene ($C_4H_4S$):** - 5-membered ring with S lone pair contributing to conjugation - Total π electrons: 4 (from double bonds) + 2 (from S) = **6 electrons** ✓ Aromatic - **Most aromatic** because S is less electronegative than N, making its lone pair more available for conjugation - Better orbital overlap and stronger aromatic stabilization **(C) Benzene ($C_6H_6$):** - 6 π electrons = $(4n+2)$ with $n=1$ ✓ Aromatic but less aromatic than thiophene (extra ring strain in 5-membered system makes thiophene's aromaticity more pronounced) **(D)** Incorrect — they don't all have equal aromaticity **Answer: (B)** Thiophene is most aromatic due to optimal lone pair contribution from sulfur and maximum resonance stabilization in the 5-membered aromatic system.