See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Analysis of Aromaticity To determine aromaticity, apply **Hückel's Rule**: A cyclic compound is aromatic if it has $(4n+2)$ π electrons and is planar with continuous p-orbital overlap. ## Evaluation of Each Option: **(A) Indene (benzene fused to cyclopentadiene)** - Benzene ring: 6 π electrons (aromatic) - Entire fused system: 8 π electrons total - Follows $4n+2$ rule ($n=1$): **Aromatic** ✓ **(B) Sodium salt (cyclobutadienone derivative)** - 4-membered ring with alternating C=O bonds - Forms a stable aromatic anion through resonance with sodium counterions - Demonstrates aromaticity through stabilization: **Aromatic** ✓ **(C) Naphthalene (two fused benzene rings)** - Despite having 10 π electrons ($4n+2$, $n=2$) - The central C-C bond between the rings experiences significant **non-aromaticity** - This bond has partial double-bond character, making it shorter and stronger than a typical single bond - The two rings partially lose aromaticity in the fusion region - **NOT fully aromatic** ✗ **(D) Pyran (oxygen-containing 6-membered ring)** - Oxygen contributes 2 lone pair electrons that occupy the p-orbital - Total: 6 π electrons in the aromatic system ($4n+2$, $n=1$) - Planar with continuous π overlap: **Aromatic** ✓ ## Answer: **(C) is not aromatic** Naphthalene's fused ring system creates structural constraints that compromise full aromaticity, unlike the other compounds which maintain continuous aromatic character.