See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Geometrical Isomerism Analysis Geometrical (cis-trans) isomerism requires: - A C=C double bond with **two different groups on each carbon** Let me check each compound: **(1) 2-butene:** $CH_3-CH=CH-CH_3$ - Each carbon of the double bond has different groups (H and alkyl) - **Shows cis-trans isomerism** ✓ **(2) 2-pentene:** $CH_3-CH=CH-CH_2-CH_3$ - Each carbon of the double bond has different groups - **Shows cis-trans isomerism** ✓ **(3) 2,3-dibromo-2-butene:** $CH_3-CBr=CBr-CH_3$ - Both carbons of the double bond have: one methyl and one bromine - **Shows cis-trans isomerism** ✓ **(4) 2-methyl propene:** $(CH_3)_2C=CH_2$ - Left carbon: two identical methyl groups - Right carbon: two identical hydrogen atoms - **Cannot show cis-trans isomerism** ✗ **Answer: (4) 2-methyl propene** does not show geometrical isomerism because the double bond carbons don't have two different substituents each. The left carbon has identical methyl groups, violating the requirement for geometrical isomers.