See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Analysis of Most Stable Conformation **Identify the molecule:** This is 2,2,3,3-tetramethylbutane viewed along the C2-C3 bond (Newman projection). **Stability principle:** Stability depends on minimizing steric strain. The most stable conformation has: - Large groups in **gauche positions** (not eclipsed) - Bulky substituents **staggered** relative to each other **Evaluate each option:** **(A)** Two methyls eclipsed on one side → High steric repulsion ✗ **(B)** All four methyls positioned **gauche to each other** in a staggered arrangement → Substituents maximally separated with no eclipsing ✓ **(C)** Methyls partially eclipsed → Moderate strain ✗ **(D)** Methyls eclipsed → High steric repulsion ✗ **Why B is correct:** In option B, the four methyl groups are arranged in an alternating staggered pattern around the C2-C3 bond. Each methyl group occupies a gauche position relative to the others, maximizing spatial separation and minimizing van der Waals repulsion. This is the **anti-periplanar arrangement** for bulky groups, which is thermodynamically most favorable. **Answer: (B)**