See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Analysis of Molecular Stability at Room Temperature ## Option (B) — Cyclobutene **Unstable** — Small four-membered ring with a C=C double bond - High ring strain due to restricted bond angles (~90°) - The double bond cannot achieve optimal sp² geometry - Undergoes rapid ring-opening polymerization at room temperature - Thermodynamically unfavorable ## Option (C) — Cyclopentadienone **Unstable** — Five-membered ring with a C=O double bond conjugated with diene - Contains an anti-aromatic system (4π electrons in conjugation following Hückel's rule) - Anti-aromatic systems are thermodynamically destabilized - Undergoes rapid Diels-Alder dimerization via self-coupling - Cannot exist in pure form at room temperature --- ## Why Others Are Stable: **(A) Benzene** — Aromatic (6π electrons), extremely stable due to resonance and delocalization **(D) Cycloheptatrienone** — Seven-membered ring; the carbonyl stabilizes the system rather than creating anti-aromaticity, making it reasonably stable **Answer: B and C** are both unstable due to ring strain (B) and anti-aromaticity (C), respectively.