See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Ranking Phenolic Acidity Using Resonance Arguments **Key Principle:** Electron-withdrawing groups stabilize the phenoxide anion (conjugate base), increasing phenolic acidity. ## Analysis of Each Compound: **Compound I: 4-Chlorophenol** - $Cl$ is weakly electron-withdrawing (by inductive effect) - Modest stabilization of the phenoxide anion - Moderate acidity **Compound II: 4-Trifluoromethylphenol** - $CF_3$ is **highly electron-withdrawing** (three electronegative F atoms pull electron density) - Strong inductive withdrawal stabilizes the negative charge on phenoxide - **Highest acidity** **Compound III: 4-Fluorophenol** - $F$ is very electronegative but also a weak **resonance donor** (lone pairs on F donate to benzene ring) - This *destabilizes* the phenoxide anion by increasing negative charge density - Actually **less acidic than phenol itself** ## Acidity Order: $$\text{II} > \text{I} > \text{III}$$ The $CF_3$ group (inductive withdrawal dominates) > $Cl$ group (moderate withdrawal) > $F$ group (resonance donation outweighs withdrawal) **Answer: (A) I > II > III** ✓ This ranking reflects that electron-withdrawing inductive effects increase acidity, while electron-donating resonance effects decrease it.