See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Analysis of Conformational Isomerism Statements **Evaluating each option:** **(A) False** — Eclipsed and staggered ethanes both lack substituents on the same carbons, so free radical chlorination produces identical monochlorination products ($CH_3CH_2Cl$). Conformation doesn't affect the product, only the reaction rate (staggered reacts faster due to lower strain). **(B) False** — Conformational isomers (rotamers) have low energy barriers ($\approx 12$ kJ/mol for ethane). At room temperature, rapid rotation occurs, making it impossible to isolate individual conformers. **(C) TRUE** — **Torsional strain in ethane:** - At dihedral angle $0°$ (eclipsed): maximum strain - At dihedral angle $60°$ (staggered): minimum strain - At dihedral angle $180°$ (eclipsed): maximum strain again - At dihedral angle $300°$ (= $-60°$, staggered): **minimum strain** ✓ The three staggered conformations ($60°, 180°, 300°$) all have equivalent minimum torsional strain due to symmetry. **(D) False** — In n-butane, **gauche form** ($60°$ dihedral angle between terminal methyls) experiences significant **steric strain** from methyl-methyl interactions. The **anti form** ($180°$) is the actual minimum-strain conformation. **Answer: (C)** is correct because torsional strain reaches its minimum at all three staggered configurations including $60°$, $180°$, and $300°$ dihedral angles.