See image — Aromatic Hydrocarbons Chemistry Question

💡 Solution & Explanation

Concept: Positional isomers arise when substituents can occupy different positions on a benzene ring. For dichloronitrobenzene, the molecule has three substituents on benzene: two Cl atoms and one NO2 group (total three substituents on a six-membered ring). Step 1: Fix the NO2 group and determine the possible positions of the two Cl atoms relative to NO2. Step 2: With NO2 fixed at position 1, the two Cl atoms can be placed at various combinations of the remaining positions (2, 3, 4, 5, 6). Using symmetry of benzene, unique positions for two Cl atoms relative to NO2 at C1: - Cl at 2,3 (both ortho/meta) - Cl at 2,4 (ortho and para) - Cl at 2,5 (both ortho positions on opposite sides) - Cl at 2,6 (both ortho, symmetric) - Cl at 3,4 (meta and para adjacent) - Cl at 3,5 (both meta) Step 3: Count unique isomers by considering mirror symmetry: 1. 1-NO2, 2,3-diCl 2. 1-NO2, 2,4-diCl 3. 1-NO2, 2,5-diCl 4. 1-NO2, 2,6-diCl 5. 1-NO2, 3,4-diCl 6. 1-NO2, 3,5-diCl All six are distinct structures. 2,6-diCl is symmetric (Cl on both ortho positions), so it is one unique isomer. Step 4: Total = 6 isomers. Why other options fail: - (a) 3: Too few; ignores many positional combinations. - (b) 4: Undercounts; misses some unique arrangements. - (d) 8: Overcounts; does not account for benzene ring symmetry properly. Therefore, the correct answer is C.