See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Identifying Meso Compounds **Key Definition:** A meso compound has two or more chiral centers but is achiral overall due to an internal plane of symmetry. ## Analysis of Each Structure: **Structure (1):** 2,3-dichlorobutane with stereochemistry $H$ and $Cl$ on opposite sides - Draw a vertical plane through the central $C$-$C$ bond - Left chiral center: $(R)$-configuration - Right chiral center: $(S)$-configuration - These are **non-superimposable mirror images** = enantiomers - **Not meso** ❌ **Structure (2):** Same compound, but with $H$ and $Cl$ on the **same side** - The plane of symmetry passes through the molecule - Left half mirrors the right half perfectly - Both chiral centers have opposite $(R)/(S)$ assignments that cancel - **This is meso** ✓ **Structure (3):** Examination shows $Cl$ atoms are on the same side relative to the $C$-$C$ bond - Lacks internal plane of symmetry - The two chiral centers are not related by symmetry - **Not meso** ❌ ## Conclusion: Only structure **(2)** possesses a plane of symmetry making it achiral despite having chiral centers. **Answer: (A) Only (1)** is incorrect — the correct answer is **(B) Only (2)**.