See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Monochlorinated Structural Isomers Analysis We need to find which compounds can form **exactly 2 structural isomeric monochlorinated derivatives**. ## Option (A): n-Butane Structure: $CH_3-CH_2-CH_2-CH_3$ Possible chlorination positions: - **Primary position** ($CH_3$ group): $ClCH_2-CH_2-CH_2-CH_3$ → 1 isomer - **Secondary position** ($CH_2$ group): $CH_3-CHCl-CH_2-CH_3$ → 1 isomer **Total: 2 isomers** ✓ (due to symmetry, internal $CH_2$ groups are equivalent) ## Option (B): 2,4-Dimethyl pentane Structure: $(CH_3)_2CH-CH_2-CH(CH_3)_2$ Possible positions: - Methyl groups on C2 (2 equivalent) - Methyl groups on C4 (2 equivalent) - Central $CH_2$ group **Total: 3 different isomers** ✗ ## Option (C): Benzene Structure: $C_6H_6$ (hexagonal ring) All six hydrogens are **equivalent by symmetry**. Monochlorination gives only **1 isomer**: chlorobenzene **Total: 1 isomer** ✗ ## Option (D): 2-Methyl propane Structure: $(CH_3)_3C-H$ (isobutane) Possible positions: - **Primary positions** (three equivalent $CH_3$ groups): $ClCH_2-C(CH_3)_3$ → 1 isomer - **Tertiary position** (central $CH$): $(CH_3)_3C-Cl$ → 1 isomer **Total: 2 isomers** ✓ (due to symmetry of three identical methyl groups) --- **Both A and D yield exactly 2 monochlorinated structural isomers due to molecular symmetry reducing the number of unique substitution positions.**