Question

Correct stability order of alkene ::

• A. $\text{A}>\text{D}>\text{C}>\text{B}$
• B. $\text{D}>\text{A}>\text{B}>\text{C}$
• C. $\text{A}>\text{D}>\text{B}>\text{C}$
• D. $\text{B}>\text{C}>\text{D}>\text{A}$

Hint:

Stability of alkenes increases with hyperconjugation (more $\alpha\text{H}$). Among isomers with the same degree of substitution, $\text{trans}$ is more stable than $\text{cis}$ due to lower steric hindrance.

Answer 1

The Correct Option is A

The stability of alkenes is generally determined by the number of $\alpha$-hydrogens ($\alpha\text{H}$) (hyperconjugation) and minimized steric repulsion ($\text{trans}$ $>$ $\text{cis}$).
$\text{A} (1-\text{Butene})$: $2 \alpha\text{H}$ (Monosubstituted). 
$\text{B} (\text{cis}-2-\text{Butene})$: $6 \alpha\text{H}$ ($\text{cis}$). 
$\text{C} (\text{trans}-2-\text{Butene})$: $6 \alpha\text{H}$ ($\text{trans}$). 
$\text{D} (\text{isobutene})$: $6 \alpha\text{H}$ (Di-substituted terminal). 
Standard stability order: $\text{A}>\text{D}>\text{C}>\text{B}$. (Di-substituted is more stable than Mono-substituted).