See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Geometrical Isomerism in Alkenes **Requirement for geometrical isomerism:** An alkene must have **two different groups on each carbon** of the double bond. Let me analyze each option: **(1) $CH_3CH=CHCH_3$ (But-2-ene)** - Left C of double bond: $CH_3$ and $H$ - Right C of double bond: $CH_3$ and $H$ - ✓ Both carbons have different groups → **Shows cis-trans isomerism** **(2) $(CH_3)_2C=C(CH_3)_2$** - Left C: two $CH_3$ groups (identical) - Right C: two $CH_3$ groups (identical) - ✗ No geometrical isomerism (no distinct isomers possible) **(3) $(CH_3)_2C=CH_2$** - Left C: two $CH_3$ groups (identical) - Right C: two $H$ atoms (identical) - ✗ No geometrical isomerism (symmetrical) **(4) $CH_3-CH=C(CH_3)_2$** - Left C: $CH_3$ and $H$ ✓ - Right C: two $CH_3$ groups (identical) - ✗ Right carbon lacks two different groups; no isomerism possible **Answer: (1)** — Only but-2-ene has different substituents on **both** carbons of the double bond, allowing *cis* and *trans* forms.