Question

Which alkene in the following is most stable?

• A. 1-butene
• B. 2-butene
• C. 1-pentene
• D. 2-pentene

Answer 1

Answer: (B)

Stability of alkene $\alpha$ no. of hyper conjugating structures $\propto$ no. of $\text{α-H}$

${\text{CH}}_{\text{3}}-\stackrel{\text{α}}{{\text{CH}}_{\text{2}}}-\text{CH}\text{=}{\text{CH}}_{\text{2}}\text{2}\text{H}\text{.C}\text{.}$

$\stackrel{\text{α}}{{\text{CH}}_{\text{3}}}-\text{CH}=\text{CH}-\stackrel{\text{α}}{{\text{CH}}_{\text{3}}}6\text{H}\text{.C}\text{.}$

${\text{CH}}_{\text{3}}-{\text{CH}}_2-\stackrel{\text{α}}{{\text{CH}}_{\text{2}}}-\text{CH}\text{=}{\text{CH}}_{\text{2}}2\text{H}\text{.C}\text{.}$

${\text{CH}}_{\text{3}}-\stackrel{\text{α}}{{\text{CH}}_2}-\text{CH}=\text{CH}-\stackrel{\text{α}}{{\text{CH}}_{\text{2}}}5\text{H}\text{.C}\text{.}$