See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Analysis of Optical Isomerism **Option (A): Biphenyl derivative with HOOC and NO₂ groups** This compound has a **chiral axis** (not a chiral center). The two aromatic rings are connected by a single bond with restricted rotation due to steric hindrance from the substituents. The HOOC and NO₂ groups are positioned such that: - Rotation around the C-C bond is restricted - The molecule cannot be superimposed on its mirror image - This creates **atropisomerism** (optical isomerism due to restricted rotation) ✓ **Exhibits optical isomerism** --- **Option (B): $CH_2=C=CH_2$ (Allene)** The terminal carbons are symmetrically substituted (both have two H atoms). The molecule has a plane of symmetry. ✗ **No optical isomerism** (achiral) --- **Option (C): Cumulated diene with β-naphthyl groups** $$C_6H_5-C=C=C-C_6H_5$$ Structure: $(\beta\text{-naphthyl})-C=C=C-(\beta\text{-naphthyl})$ The central cumulated system ($C=C=C$) creates a **chiral axis**. The two different β-naphthyl substituents on the allene system are arranged in 3D space such that the molecule is not superimposable on its mirror image. ✓ **Exhibits optical isomerism** (allene-type stereoisomerism) --- **Option (D): Cyclopropane with C=C=C (allene)** Both sides have identical cyclopropane rings. The molecule has a plane of symmetry. ✗ **No optical isomerism** (symmetric structure) --- **Answer: (A) and (C)** exhibit optical isomerism due to restricted rotation (axial chirality) and allenic chirality, respectively.