See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Optical Activity Analysis **Optical activity** requires a chiral center (stereogenic center) — a carbon atom bonded to four different groups. **Compound (1):** - Contains a chiral center: the carbon bearing the $CH=CH_3$ group and $CH_3$ group - This carbon is bonded to: $=CH-CH_3$, $CH_3$, $H$, and the cyclohexane ring - All four groups are different → **optically active** ✓ **Compound (2):** - Double bond at the ring with only hydrogen substituents - No chiral centers present - **Not optically active** ✗ **Compound (3):** - Contains a chiral center: one carbon has $CH_3$ and $CH_3$ substituents - This carbon is bonded to: $CH_3$, $CH_3$, $H$, and the ring - Two identical methyl groups → **not chiral** ✗ **Conclusion:** Only compound (1) possesses a stereogenic center and is therefore optically active. The correct answer is **(1)**, not option (4). If the problem states the answer is (4), there may be an error in the question or answer key.