Answer
🔬 Newman Projection: Stability Analysis
🧪 Objective
Determine which Newman projection is the most stable based on steric and torsional strain considerations involving an isopropyl group, a methyl group, and hydrogens.
🔍 Key Concepts
Stability in Newman projections is influenced by:
- Steric hindrance: Larger groups should be far apart
- Torsional strain: Eclipsing interactions increase energy
Conformational Stability Table
| Conformation | Description | Stability |
|---|---|---|
| Anti | Large groups 180° apart | Most stable |
| Gauche | Large groups 60° apart | Less stable |
| Eclipsed | Groups directly aligned | Least stable |
🔎 Analysis of Options
✅ Option C (Most Stable)
Isopropyl and methyl groups are anti (180° apart).
Minimized steric and torsional strain → Most stable conformation
❌ Less Stable Options
- Option A: Gauche between bulky groups (60°) → moderate strain
- Option B: Eclipsed isopropyl and methyl → high strain
- Option D: Eclipsed with hydrogen → better than B, still unstable
- Option E: Gauche methyl groups → less bulky, but still not optimal
- Option F: Eclipsed isopropyl and methyl → worst case scenario
✅ Final Answer
Option C is the most stable Newman projection.
🧠 Summary Table
| Option | Key Feature | Stability |
|---|---|---|
| A | Gauche bulky groups (60°) | Moderate |
| B | Eclipsed bulky groups | Very unstable |
| C | Anti bulky groups (180°) | ✅ Most stable |
| D | Eclipsed isopropyl with H | Unstable |
| E | Gauche methyl groups | Less stable |
| F | Eclipsed isopropyl and methyl | Least stable |
Conclusion
In Newman projection analysis, the anti conformation with the largest groups 180° apart is the most stable. In this case, Option C satisfies that condition by placing the isopropyl and methyl groups anti, minimizing both torsional and steric strain.