See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Enol Content Analysis **Key Principle:** Enol content increases with: - Conjugation (extended $\pi$-system stabilizes enolate) - Aromaticity (aromatic rings stabilize enolic form) - Electron-withdrawing adjacent heteroatoms --- ## Analysis of Each Compound: **Compound (I) - Cyclohexanone:** - Simple ketone, no conjugation - Minimal enol content (~0.0001%) **Compound (II) - δ-Valerolactone (6-membered lactone):** - Carbonyl conjugated with oxygen in ring - Oxygen donation stabilizes enolate - Moderate enol content **Compound (III) - Acetone:** - Simple aliphatic ketone - No conjugation or aromatic stabilization - Very low enol content (~10⁻⁸) **Compound (IV) - Pyridin-3-one:** - Aromatic heterocycle (partially aromatic even in keto form) - Nitrogen's electron-withdrawing effect activates α-H - Enolate gains aromatic resonance stabilization - **Highest enol content** by far --- ## Decreasing Order: **IV > II > I > III** **Option A (4 > 1 > 3 > 2)** correctly maps this as: IV > I > III > II ✓ The aromatic pyridine ring in (IV) makes it by far the most enolizable; simple ketone (I) beats acetone (III) due to ring strain effects; lactone (II) has lowest enol content despite conjugation.