See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Acidity of Phenolic Compounds **Key Principle:** Acidity of phenols depends on stability of the phenoxide ion ($C_6H_5O^-$). Electron-withdrawing groups stabilize it (increase acidity); electron-donating groups destabilize it (decrease acidity). ## Analysis of Each Compound: **I. p-Nitrophenol** ($NO_2$ at para position) - $NO_2$ is a strong electron-withdrawing group (EWG) - Withdraws electrons via inductive and resonance effects - Stabilizes the phenoxide ion significantly - **Highest acidity** ✓ **IV. Phenol** (parent compound) - No substituent; baseline acidity - $pK_a \approx 10$ **II. p-Cresol** (CH₃ at para position) - $CH_3$ is electron-donating (EDG) but weakly - Slightly destabilizes phenoxide vs. phenol - Acidity: slightly less than phenol **III. m-Cresol** (CH₃ at meta position) - $CH_3$ is EDG (same as p-cresol) - Meta position allows slightly less resonance stabilization of positive charge buildup - Acidity: slightly less than p-cresol - **Lowest acidity** ✓ ## Order of Decreasing Acidity: $$\boxed{\text{I} > \text{II} > \text{III} > \text{IV}}$$ **Answer: (A)** — p-Nitrophenol is most acidic (EWG effect), followed by the two cresols (EDG), with phenol least acidic.