See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Identifying Asymmetric Centre An asymmetric centre (chiral centre) is a carbon atom bonded to **four different groups**. **Analysis of each option:** **(1) 2-Butene:** $CH_3-CH=CH-CH_3$ - Contains a C=C double bond; sp² carbons cannot be chiral centres - ❌ No asymmetric centre **(2) 2,2-Dimethylpropane:** $C(CH_3)_4$ - Central carbon bonded to four identical methyl groups - ❌ No asymmetric centre (not four different groups) **(3) 2-Hexyne:** $CH_3-C≡C-CH_2-CH_2-CH_3$ - Contains a C≡C triple bond; sp carbons cannot be chiral centres - ❌ No asymmetric centre **(4) Lactic acid:** $CH_3-CHOH-COOH$ - The carbon bearing the $-OH$ group is bonded to: - $CH_3$ (methyl) - $H$ (hydrogen) - $OH$ (hydroxyl) - $COOH$ (carboxyl) - All four groups are **different** ✓ - ✅ **Contains one asymmetric centre** **Answer: (4) Lactic acid** — it has a chiral centre at the $\alpha$-carbon.