See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

**Step 1: Identify the molecular formula** Both compounds A and B have the same molecular formula: $C_5H_8O_6$ - Compound A: $COOCH_3$, $COOH$, and two $OH$ groups on a 2-carbon chain - Compound B: $COOH$, $COOCH_3$, and two $OH$ groups on a 2-carbon chain **Step 2: Identify stereogenic centers** Both A and B have **one chiral center** (the central carbon bearing $H$, $OH$, $COOH/COOCH_3$, and $OH/COOCH_3$). **Step 3: Compare stereochemistry** - **Compound A**: The chiral center has the configuration with $COOCH_3$ at top and $COOH$ at bottom - **Compound B**: The chiral center has the configuration with $COOH$ at top and $COOCH_3$ at bottom These are **opposite orientations** of the same four groups around the chiral center. **Step 4: Determine relationship** When two compounds: - Have the same molecular formula ✓ - Have one chiral center ✓ - Have opposite configurations at that center ✓ They are **enantiomers** (non-superimposable mirror images). **Answer: (3) A and B are enantiomers**