See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Analysis of Stereoisomerism in Compounds (I) and (II) **Step 1: Identify the stereogenic center** Both structures contain a chiral center (the carbon bearing the $CHO$ group with four different groups attached). **Step 2: Assign R/S configuration to Compound (I)** Using priority rules (atomic number): - $CHO$ (1), $OH$ (2), $H$ (4), $C_6H_5$ (3) - Tracing 1→2→3 gives **R-configuration** - With $H$ wedged (forward), this is the **threo form** **Step 3: Assign R/S configuration to Compound (II)** - $CHO$ (1), $OH$ (2), $H$ (4), $C_6H_5$ (3) - Tracing 1→2→3 gives **S-configuration** - With $H$ wedged (forward), this is the **threo form** **Step 4: Evaluate the options** **(A) Both are in threo form** ✓ **CORRECT** - Both have the characteristic threo arrangement (same stereochemistry at both chiral positions when viewed in Fischer projection) **(B) Both are enantiomers** ✓ **CORRECT** - Compound (I) is **R-configuration** at the top center - Compound (II) is **S-configuration** at the top center - They are non-superimposable mirror images = enantiomers **(C) Both are diastereomers** ✗ Incorrect - Diastereomers differ at some but not all chiral centers; these differ at all centers **(D) Both are in erythro form** ✗ Incorrect - Neither exhibits erythro stereochemistry **Answer: (A) and (B) are both correct**