See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

## Analysis of Keto Isomers of Hexahydroxybenzene **Step 1: Identify the starting compound** The given compound is hexahydroxybenzene ($C_6H_6O_6$) — a benzene ring with 6 OH groups. **Step 2: Understand keto-enol tautomerism** Keto isomers form when OH groups on aromatic rings undergo tautomerization to C=O (carbonyl) groups. The aromatic ring becomes a non-aromatic cyclohexadiene or cyclohexanone system. **Step 3: Evaluate stability criteria** For maximum stability of the keto isomer: - **Conjugation**: Alternating C=O and C=C bonds (conjugated system) increases stability - **Symmetry**: Symmetric arrangement minimizes strain and electronic repulsion - **Resonance**: Extended conjugation through the ring stabilizes the structure **Step 4: Analyze each option** - **(A)** Triketone with 3 C=O groups — excessive carbonyl clustering causes strain and repulsion - **(B)** Asymmetric arrangement — less stable due to broken symmetry and incomplete conjugation - **(C)** **Alternating pattern**: C=O at positions 1,3,5 with OH at positions 2,4,6 — creates perfect conjugation around the ring ($-C(=O)-C(OH)-C(=O)-C(OH)...$) with maximum resonance stabilization and symmetry - **(D)** Asymmetric arrangement — lacks the optimal conjugation of option C **Answer: (C)** is most stable because the alternating keto-enol arrangement maximizes conjugation, maintains full ring symmetry, and distributes electronic density most favorably through resonance.