See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Solution for (d) trans-1-ethyl-3-methylcyclohexane ## Step 1: Draw the two chair conformers For **trans-1-ethyl-3-methylcyclohexane**, the ethyl and methyl groups are on opposite sides (trans) at positions 1 and 3. **Conformer 1:** Ethyl axial, Methyl equatorial **Conformer 2:** Ethyl equatorial, Methyl axial ## Step 2: Identify steric interactions - **Conformer 1 (axial ethyl):** The ethyl group is bulky and occupies an axial position → severe 1,3-diaxial interactions with H atoms on C2 and C6 - **Conformer 2 (equatorial ethyl):** The ethyl group is equatorial → only the methyl group is axial (small, minimal strain) ## Step 3: Apply stability principles Larger substituents prefer equatorial positions to minimize axial strain. Since ethyl (bulkier than methyl) is equatorial in Conformer 2, this arrangement experiences significantly less steric hindrance. ## Step 4: Conclusion **Conformer 2 (ethyl equatorial, methyl axial) is more stable** because it minimizes the steric clash of the bulkier ethyl group with axial hydrogens. $$\boxed{\text{Conformer with equatorial ethyl is favored}}$$ This demonstrates that in trans-disubstituted cyclohexanes, the larger group preferentially adopts the equatorial position for maximum stability.