See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Phenol Acidity Comparison **Key Principle:** Phenol acidity depends on stability of the phenoxide ion ($C_6H_5O^-$). More stable conjugate base = stronger acid. ## Analysis of Each Option: **(A) Acetic acid ($CH_3COOH$)** — MORE ACIDIC than phenol - $pK_a$ (acetic acid) ≈ 4.75 - $pK_a$ (phenol) ≈ 10 - Carboxylic acids are much stronger acids due to resonance stabilization and electron-withdrawing carbonyl group - **Phenol is LESS acidic than acetic acid** ✓ **(B) p-methoxy phenol** — LESS ACIDIC than phenol - $-OCH_3$ group is electron-donating (activating) - Destabilizes the phenoxide ion by pushing electron density into the ring - Decreases acidity compared to phenol - **Phenol is MORE acidic** ✗ **(C) p-nitrophenol** — MORE ACIDIC than phenol - $-NO_2$ group is electron-withdrawing (deactivating) - Stabilizes the phenoxide ion through resonance - $pK_a$ (p-nitrophenol) ≈ 7.15 vs phenol ≈ 10 - **Phenol is LESS acidic than p-nitrophenol** ✓ **(D) Ethanol ($C_2H_5OH$)** — MUCH LESS ACIDIC than phenol - Aliphatic alcohols are very weak acids - Phenol is ~$10^{15}$ times more acidic - **Phenol is MORE acidic** ✗ **Answer: (A) and (C)** are correct because phenol is less acidic than both acetic acid and p-nitrophenol.