Question

Arrange the above alkenes in increasing order of their heat of hydrogenation explaining the reason for your choice.

Answer 1

Trans alkene is more stable than cis alkene.

Also, more substituted alkene is more stable than less substituted alkene.

Hence, the decreasing order of the stability of alkenes is $\left(iv\right)>\left(ii\right)>\left(iii\right)\simeq \left(v\right)>\left(i\right)$ .

More stable alkene has a lower heat of hydrogenation.

Hence, the increasing order of the heat of hydrogenation is $\left(iv\right)<\left(ii\right)<\left(iii\right)\simeq \left(v\right)<\left(i\right)$ .