See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Stereoactive Isomers of Butane-2,3-diol **Structure:** $CH_3-CHOH-CHOH-CH_3$ **Step 1: Identify chiral centers** - Carbon 2 ($C_2$): bonded to $-OH$, $-H$, $-CH_3$, and $-CHOHCH_3$ → **chiral** - Carbon 3 ($C_3$): bonded to $-OH$, $-H$, $-CH_3$, and $-CHOHCH_3$ → **chiral** Two chiral centers exist. **Step 2: Determine possible stereoisomers** With 2 independent chiral centers: $2^n = 2^2 = 4$ possible stereoisomers - $(2R, 3R)$ - $(2S, 3S)$ - $(2R, 3S)$ - $(2S, 3R)$ **Step 3: Check for meso compounds** The $(2R, 3S)$ and $(2S, 3R)$ isomers are **enantiomers of each other** (not meso, since the molecule lacks an internal plane of symmetry). **Step 4: Count optically active isomers** Optically active compounds exclude meso compounds. Here: - $(2R, 3R)$ → optically active ✓ - $(2S, 3S)$ → optically active ✓ - $(2R, 3S)$ and $(2S, 3R)$ → form an enantiomeric pair, counting as **2 optically active isomers** **Total optically active stereoisomers = 2** **Answer: (B) 2**