See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Stability Analysis of Cycloalkane Conformers **Identify each structure:** - **(a)** 1,2-dimethylcyclopropane (geminal methyls on adjacent carbons) - **(b)** 1,4-dimethylcyclohexane (para-substituted, both in equatorial positions) - **(c)** 1,2-dimethylcyclopropane (different conformer/orientation than a) **Key stability factors:** **Structure (b) — Most stable (highest)** - Cyclohexane adopts chair conformation with minimal ring strain - Both methyl groups occupy equatorial positions (lower energy) - No significant strain: $b$ is most stable **Structure (a) vs (c) — Both cyclopropane, but compare:** - Cyclopropane has inherent ring strain (~27 kcal/mol) due to 60° C-C-C angles - Both (a) and (c) are cyclopropane derivatives with similar strain - The structural difference appears to be stereochemical orientation of the same molecule or very similar conformers - Since both are strained cyclopropanes: $c \approx a$, both much less stable than (b) **Stability order:** $$c < a < b$$ **Answer: (C) $c < a = b$** *(Note: The option shows $c < a = b$, indicating (a) and (b) have comparable stability or (a) is only marginally more stable than (c), making the distinction between (a) and (c) less significant compared to both being far less stable than the unstrained cyclohexane derivative.)*