See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Geometrical Isomerism Analysis **Geometrical isomerism** occurs when atoms/groups are arranged differently in space around a rigid bond (typically $C=C$ double bond), creating **cis** and **trans** isomers. ## Evaluating each option: **(1) 2-butene** ✓ **CORRECT** - Structure: $CH_3-CH=CH-CH_3$ - The $C=C$ double bond is rigid, and both carbons have different groups attached - **cis-2-butene**: both $CH_3$ groups on same side - **trans-2-butene**: $CH_3$ groups on opposite sides - This clearly shows geometrical isomerism **(2) 2-butyne** ✗ - Structure: $CH_3-C \equiv C-CH_3$ - Triple bonds are linear (180°); no spatial variation possible - No geometrical isomerism **(3) 2-butanol** ✗ - Structure: $CH_3-CHOH-CH_3$ - Single bond allows free rotation - No rigid geometry, only stereoisomerism (optical) **(4) Butanal** ✗ - Structure: $CH_3CH_2CH_2CHO$ - Contains only single bonds (free rotation) - No geometrical isomerism **Answer: (1) 2-butene** is the only compound with a $C=C$ double bond allowing restricted rotation, thereby exhibiting geometrical isomerism.