See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

## Analysis of 2-Methyl Butane Conformational Energy **Structure:** 2-methyl butane has two methyl groups ($CH_3$) on the central C-C bond being rotated. **Key Conformations during Anticlockwise Rotation:** 1. **At 0°:** Eclipsed conformation with both methyls aligned → **High energy (maximum)** 2. **At 60°:** Staggered conformation → **Lower energy (local minimum)** 3. **At 120°:** Eclipsed again, but with methyls at 120° → **High energy (secondary maximum)** 4. **At 180°:** Staggered conformation (opposite of 0°) → **Lower energy (local minimum)** **Why Option B is Correct:** - **0° to 60°:** Energy decreases from maximum (eclipsed) to minimum (staggered) - **60° to 120°:** Energy increases back to a maximum at 120° (eclipsed) - **120° to 180°:** Energy decreases again toward minimum Option B shows two similar-height maxima at 60° and 120°, with the first maximum **lower than the second**—this is characteristic of 2-methyl butane where the two methyl groups create slightly asymmetric steric interactions, making the 120° eclipse (methyl-methyl gauche) slightly higher in energy than the 0° eclipse. **Answer: B**