See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

**Step 1: Identify all acidic hydrogens** The molecule contains four $OH$ groups (phenolic and carboxylic acid). We need to determine which hydrogen is most easily donated to a base (most acidic). **Step 2: Compare acidic strengths** - **Position 4 (Carboxylic acid $-COOH$):** The hydrogen is attached to oxygen in a $C=O$ system. The carbonyl group is highly electron-withdrawing, which stabilizes the resulting negative charge through resonance and inductive effects. - **Positions 1, 2, 3 (Phenolic $-OH$):** These are phenol hydrogens bonded directly to an aromatic ring. While phenols are weak acids, they are significantly less acidic than carboxylic acids. **Step 3: Apply acidity principles** Carboxylic acids ($pK_a \approx 4$) are much stronger acids than phenols ($pK_a \approx 10$) because: - The conjugate base ($COO^-$) is stabilized by resonance with the $C=O$ double bond - Electron withdrawal by the carbonyl oxygen weakens the $O-H$ bond **Step 4: Conclusion** The hydrogen at position 4 is the most acidic and will be most readily donated to a base. **Answer: (B) 4**