See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Analysis of Enantiomerism To exist as enantiomers, a compound must contain a **chiral center** (stereogenic center) — a carbon bonded to four different groups. ## Evaluation of each compound: **(1) $CH_3CH(OH)CO_2H$** - Central carbon has: $-CH_3$, $-OH$, $-CO_2H$, $-H$ (all different) - **Has a chiral center** → exists as enantiomers ✓ **(2) $CH_3CH_2CH(CH_3)CH_2OH$** - The carbon bearing $-CH_3$ has: $-CH_3$, $-CH_2CH_3$, $-CH_2OH$, $-H$ (all different) - **Has a chiral center** → exists as enantiomers ✓ **(3) $C_6H_5CH_2CH_3$ (Ethylbenzene)** - All carbons lack four different groups: - Aromatic carbons have C-C-C-H bonds (not four different) - $CH_2$ carbon has: $-C_6H_5$, $-CH_3$, $-H$, $-H$ (two H atoms are identical) - **No chiral center** → **CANNOT exist as enantiomers** ✗ **(4) $C_6H_5CHClCH_3$ (α-Chloroethylbenzene)** - The $CHCl$ carbon has: $-C_6H_5$, $-Cl$, $-CH_3$, $-H$ (all different) - **Has a chiral center** → exists as enantiomers ✓ **Answer: (3)** — Ethylbenzene has no chiral center because the $CH_2$ carbon possesses two identical hydrogen atoms.