See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

**Step 1: Determine molecular formula of propanoic acid** Propanoic acid: $CH_3CH_2COOH$ has molecular formula $C_3H_6O_2$ **Step 2: Determine molecular formulas of each option** (1) $CH_3-C(=O)-OC_2H_5$ (ethyl acetate) → $C_4H_8O_2$ ✗ (2) $HOCH_2CH_2CHO$ (3-hydroxypropanal) → $C_3H_6O_2$ ✓ (3) $CH_3CH(OH)CH_3$ (propan-2-ol) → $C_3H_8O$ ✗ (4) $CH_3O-CH_2-CH_2OH$ (2-methoxyethanol) → $C_3H_8O_2$ ✗ **Step 3: Verify isomerism** Only option (2) has the same molecular formula $C_3H_6O_2$ as propanoic acid, making them **functional group isomers**: - Propanoic acid: carboxylic acid functional group - 3-hydroxypropanal: aldehyde + alcohol functional groups **Answer: Option (2)** is isomeric with propanoic acid because both share the molecular formula $C_3H_6O_2$ but differ in functional groups (structural isomerism).