Which of the following alkenes will show the highest heat of hydrogenation per double bond?

Solution

1. Heat of hydrogenation is a measure of alkene stability.
2. Less substituted alkenes are generally less stable than more substituted ones.
3. $\text{1-butene}$ is a monosubstituted alkene, while the others are di- or tri-substituted.
4. The lower stability of $\text{1-butene}$ results in a higher heat of hydrogenation.
5. Hence the answer is (C).