See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Analysis of First Ionization Acidic Strength in Dicarboxylic Acids **Identify the structures:** - **I**: Malonic acid (propanedioic acid) — two $COOH$ groups separated by one $CH_2$ - **II**: Glutaric acid — two $COOH$ groups separated by three carbons - **III**: Oxalic acid — two $COOH$ groups directly connected ($HOOC-COOH$) - **IV**: Methylmalonic acid — two $COOH$ groups separated by one carbon with a methyl branch **Key principle:** First ionization strength depends on: 1. **Electron-withdrawing effect** of the second $COOH$ group (stronger when closer) 2. **Inductive stabilization** of the conjugate base by nearby electron-withdrawing groups **Order reasoning:** $$\text{III} > \text{I} > \text{IV} > \text{II}$$ - **III (strongest):** Direct attachment ($COOH-COOH$) — maximum electron-withdrawing effect from second carboxyl group; strongest inductive stabilization of $COO^-$ - **I:** Two $COOH$ separated by one carbon — strong withdrawing effect but slightly attenuated - **IV:** Methyl group is electron-donating, reduces withdrawing effect compared to I - **II (weakest):** Three carbons between carboxyls — minimal inductive effect; longest distance minimizes conjugate base stabilization **Answer: (c) III > I > IV > II** ✓