See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Optical Isomerism Condition **Optical isomerism** occurs when a compound contains a **chiral center** — a carbon atom bonded to **four different groups**. ## Step-by-step reasoning: **Step 1:** A chiral center requires the carbon atom to have **four distinct substituents** attached to it. **Step 2:** If only three groups are different (option 2), the fourth group is identical to one of them — this is not a chiral center. **Step 3:** If only two groups are different (option 3), there are repeated groups — no chirality results. **Step 4:** If all groups are the same (option 4), the carbon is achiral and shows no optical isomerism. **Step 5:** Only when **all four groups are different** (option 1) does the carbon become a stereogenic center capable of existing in two non-superimposable mirror-image forms (enantiomers). ## Conclusion: **Option (1)** is correct because optical isomerism requires a tetrahedral carbon with **four different groups** to exhibit enantiomerism and rotate plane-polarized light.