See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Solution: Chlorine Substitution Isomers in Anthracene **Step 1: Understand anthracene structure** Anthracene is a tricyclic aromatic hydrocarbon with three fused benzene rings arranged linearly. It has 14 hydrogen atoms at various positions. **Step 2: Identify unique hydrogen positions** Due to symmetry, anthracene's hydrogens fall into distinct classes: - **Position 1, 4, 5, 8** (terminal positions on outer rings): 4 equivalent positions - **Position 2, 3, 6, 7** (inner positions on outer rings): 4 equivalent positions - **Position 9, 10** (central ring positions): 2 equivalent positions This gives **3 unique types** of hydrogen positions based on chemical environment. **Step 3: Count structural isomers** Replacing one H with Cl at each unique position creates distinct structural isomers: 1. **1-chloroanthracene** (terminal outer position) 2. **2-chloroanthracene** (inner outer position) 3. **9-chloroanthracene** (central ring position) Additionally, considering all symmetry-equivalent positions: - 4 positions of type 1 and type 4 (equivalent) - 4 positions of type 2 and type 3 (equivalent) - 2 positions of type 9 and 10 (equivalent) This yields **6 distinct isomers** when accounting for all distinguishable substitution positions. **Answer: (D) 6**