See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Solution **Step 1: Identify the structures** Compound A has: - $COOCH_3$ (top), $COOH$ (bottom) - Two chiral centers with $H$, $OH$ groups Compound B has: - $COOH$ (top), $COOCH_3$ (bottom) - Same two chiral centers with $H$, $OH$ groups **Step 2: Assign stereochemistry** For A (reading top to bottom): - C1: $COOCH_3$, $OH$, $H$ → one stereochemical configuration - C2: $COOH$, $OH$, $H$ → second stereochemical configuration For B (reading top to bottom): - C1: $COOH$, $OH$, $H$ → opposite configuration at C1 vs. A - C2: $COOCH_3$, $OH$, $H$ → opposite configuration at C2 vs. A **Step 3: Determine the relationship** When we flip both the functional groups (ester ↔ acid) at both chiral centers, the stereochemical configurations at each center are inverted. This makes B the mirror image of A. **Step 4: Verify non-superimposability** The two structures cannot be superimposed on each other—they are non-superimposable mirror images. **Answer: (3) A and B are enantiomers** Enantiomers are compounds with opposite stereochemistry at all chiral centers that are non-superimposable mirror images. Options (1) and (2) are incorrect because the structures clearly differ in their spatial arrangements.