See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Solution: Benzene Derivatives with Formula $C_6H_3Cl_3$ **Step 1: Identify the structure** The molecular formula $C_6H_3Cl_3$ represents a **trichlorobenzene** — benzene with 3 chlorine atoms substituted on the ring and 3 hydrogen atoms remaining. **Step 2: Determine possible isomers** Since we have 3 identical substituents (Cl) on a benzene ring with 6 positions, we need to count distinct positional isomers based on their relative positions. **Step 3: Enumerate all isomers** 1. **1,2,3-trichlorobenzene** — three Cl atoms on consecutive carbons 2. **1,2,4-trichlorobenzene** — Cl atoms at positions 1, 2, and 4 (asymmetric pattern) 3. **1,3,5-trichlorobenzene** — three Cl atoms equally spaced (symmetric pattern) **Step 4: Verify no other isomers exist** Any other arrangement (like 1,2,5 or 1,3,4) is equivalent by symmetry to one of the three above when accounting for benzene's ring rotation. **Conclusion:** There are exactly **3 distinct positional isomers** of trichlorobenzene. **The answer is (B) 3**