JEE Main 2026 Jan 24 Shift 1, Chemistry Q3: Properties of Alkenes

Alkene stability increases with the number of $\alpha$-hydrogens (hyperconjugation) and with substitution at the double bond.

Counting $\alpha$-hydrogens:

I (tetrasubstituted): $\alpha H=12$

II (trisubstituted): $\alpha H=9$

III (disubstituted, trans): $\alpha H=6$

IV (disubstituted, cis): $\alpha H=6$

III and IV tie on hyperconjugation, but the trans isomer (III) avoids steric repulsion between the two methyl groups present in the cis isomer (IV), so III is more stable.

$\therefore$ Stability order: I > II > III > IV.