See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Keto-Enol Tautomerism Analysis **Key Principle:** Compounds with α-hydrogens adjacent to carbonyl groups undergo keto-enol tautomerism. The enol form is stabilized when conjugation or aromatic character can be achieved. ## Analysis of each compound: **(A) Cyclohexanone derivative (two adjacent carbonyls)** - α-hydrogens are present between two electron-withdrawing C=O groups - Enolization is highly favored because the resulting enol is stabilized by resonance across both carbonyls - **Exists significantly in enol form** ✓ **(B) Phenyl ketone (aromatic ring with ketone)** - The C=O is conjugated directly with the benzene ring - Enolization would break this aromatic conjugation - However, the enol form *still forms* and is stabilized by resonance with the aromatic ring, extending conjugation - **Exists in detectable enol form** ✓ **(C) 1,4-Cyclohexanedione** - Contains α-hydrogens adjacent to carbonyl groups - Similar to (A): enolization is favored due to resonance stabilization of the enol form - **Exists significantly in enol form** ✓ ## Conclusion: All three compounds have structural features that favor keto-enol tautomerism. Compounds with active α-hydrogens next to carbonyl groups, especially when enolization provides resonance stabilization or extended conjugation, exist appreciably in their enol forms. **Answer: (D) All of these**