See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Monobromination of m-Dimethyl Benzene (m-Xylene) **Step 1: Identify the starting material** m-Dimethyl benzene (m-xylene) has two methyl groups at the meta positions (1,3-positions) on the benzene ring. **Step 2: Identify reactive sites** Both $-CH_3$ groups are ortho/para directors and activate the benzene ring. Bromination can occur at: - Ortho to first $-CH_3$ group - Para to first $-CH_3$ group - Ortho to second $-CH_3$ group - Para to second $-CH_3$ group - Between the two methyl groups (meta position relative to both) **Step 3: Determine unique isomers by symmetry** Due to the symmetry of m-xylene: 1. **2,4-dibromination** (Br ortho to one $-CH_3$ and para to the other) 2. **2,5-dibromination** (Br ortho to one $-CH_3$ and meta to the other) 3. **2,6-dibromination** (Br ortho to both $-CH_3$ groups) 4. **3,5-dibromination** (Br meta to both $-CH_3$ groups) These are the only distinct isomers possible due to the symmetry plane in m-xylene. **Answer: (C) 4 isomers**