See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Aromaticity Analysis **Hückel's Rule:** A cyclic compound is aromatic if it has $(4n+2)$ π electrons and is planar with continuous p-orbital overlap. **Evaluating each option:** **(A) Benzene:** 6 π electrons = $4(1)+2$ ✓ Aromatic **(B) Quinoline:** This is a bicyclic compound with a benzene ring fused to a pyridine ring. The nitrogen atom in the pyridine portion has a lone pair in an sp² orbital (not participating in π-system). The aromatic system has 10 π electrons = $4(2)+2$ ✓ Aromatic **(C) Cyclooctatetraene:** 8 π electrons = $4(1)+4$ ✗ Non-aromatic. This compound adopts a non-planar "tub-like" conformation to avoid aromatic destabilization and ring strain. **(D) Naphthalene:** Two fused benzene rings with 10 π electrons = $4(2)+2$ ✓ Aromatic **Answer: (C) Cyclooctatetraene** is non-aromatic because it violates Hückel's rule ($8 \neq 4n+2$) and adopts a non-planar geometry that prevents continuous π-orbital overlap, preventing aromaticity.