See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Solution: Monochlorinated Isomers **Understanding the Problem:** We need to find which compound yields exactly **2 structurally isomeric monochlorinated derivatives** (where one H is replaced by Cl). --- **Analysis of Each Option:** **(A) n-pentane** ($CH_3CH_2CH_2CH_2CH_3$) - Due to symmetry: positions 1,5 are equivalent; positions 2,4 are equivalent; position 3 is unique - Gives **3 isomers** ✗ **(B) 2,4-Dimethylpentane** - Multiple distinct carbon positions due to branching - Gives **more than 2 isomers** ✗ **(D) 2,3-Dimethylbutane** - The two central carbons are equivalent by symmetry - Multiple unique positions available - Gives **more than 2 isomers** ✗ **(C) Toluene** ($C_6H_5CH_3$) - The benzene ring has **high symmetry** (6 equivalent hydrogens due to resonance) - Two positions are structurally distinct: - **Ortho/meta/para positions on the ring** → all equivalent by symmetry - **Methyl group position** → unique - **Isomers produced:** 1. Chlorine on benzene ring → **one monochlorinated product** (ortho, meta, para all identical by symmetry) 2. Chlorine on methyl group → **benzyl chloride** ($C_6H_5CH_2Cl$) ✓ **Exactly 2 structurally isomeric monochlorinated derivatives** **The answer is (C) Toluene** because ring substitution and side-chain substitution create only two distinct monochlorinated isomers.