The most stable alkene is:

[A] CH2=CH-CH2-CH3

[B] CH2=C(CH3)-CH=CH2

[C] CH2=CH-CH=CH2

[D] CH3-CH=CH-CH3

To determine which alkene is the most stable among the given options, we need to consider the concept of alkene stability, which is influenced primarily by the degree of substitution of the double bond. Generally, more substituted alkenes are more stable due to hyperconjugation and the inductive effect of alkyl groups. Let's analyze each option one by one.

Analyzing the Alkenes

• Option A: CH2=CH-CH2-CH3

This alkene has a double bond between the first and second carbon atoms. It is a terminal alkene with only one alkyl group (the -CH3) attached to the double bond. This makes it less stable compared to more substituted alkenes.

• Option B: CH2=C(CH3)-CH=CH2

This structure features a double bond between the first and second carbon, with a methyl group attached to the second carbon. It has a more complex structure with two double bonds and is less stable due to the presence of a conjugated system, which can sometimes lead to instability.

• Option C: CH2=CH-CH=CH2

This is a conjugated diene, meaning it has alternating double bonds. While conjugation can provide some stability, it is still a terminal alkene with only two alkyl groups, making it less stable than more substituted alkenes.

• Option D: CH3-CH=CH-CH3

This alkene has a double bond between the second and third carbon atoms and is a disubstituted alkene. Both carbons involved in the double bond are attached to alkyl groups (two -CH3 groups), which enhances its stability significantly compared to the other options.

Comparative Stability

In summary, the stability of alkenes increases with the number of alkyl substituents attached to the double bond. Disubstituted alkenes are generally more stable than monosubstituted or terminal alkenes. Therefore, among the options provided:

• Option A is monosubstituted.
• Option B is a more complex structure but still not as stable.
• Option C is a conjugated diene but still terminal.
• Option D is disubstituted, making it the most stable alkene.

Final Thoughts

Thus, the most stable alkene from the given choices is Option D: CH3-CH=CH-CH3. This conclusion is based on the principle that increased substitution around the double bond leads to greater stability due to the effects of hyperconjugation and steric factors. Understanding these concepts is crucial for predicting the behavior of alkenes in chemical reactions.