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 influenced by several factors, primarily the degree of substitution at the double bond and hyperconjugation. In this question, we will evaluate the stability of each alkene based on these principles.

1. Degree of Substitution: Alkenes with more alkyl groups attached to the doubly bonded carbon atoms are generally more stable. This is due to hyperconjugation and the electron-donating inductive effect of alkyl groups.
2. Hyperconjugation: More hyperconjugative structures contribute to greater stability. Each methyl group can contribute hyperconjugative resonance structures, enhancing stability.

Now, let's analyze the structures based on the image:

1. (A): This alkene is tetrasubstituted, with four alkyl groups (two on each carbon of the double bond). It experiences maximum hyperconjugation and has the highest stability.
2. (B): This alkene is monosubstituted with only one alkyl group attached, offering the least stability due to limited hyperconjugation.
3. (C): This alkene is disubstituted, possessing two alkyl groups on one carbon, which makes it more stable than a monosubstituted alkene but less stable than a trisubstituted or tetrasubstituted one.
4. (D): This alkene is trisubstituted, with three alkyl groups attached, offering a good amount of hyperconjugation but less than the tetrasubstituted alkene.

Based on this reasoning, the correct order of stability is:

\(A > D > C > B\)

Hence, the correct answer is \(A > D > C > B\).