Question

Which is the correct order for rate of hydrogenation?

• A. Hept-1-ene < Hept-3-ene < 2-Methylhex-2-ene
• B. 3-Methylcyclooctene < 1 - Methylcyclooctene < 1, 2-Dimethylcyclooctene
• C. 3-Ethyloct-1-ene < 2-Ethyloct-1-ene < Oct-2-ene
• D. Ethene < ethyne

Answer 1

The correct option is D Ethene < ethyne

Rate of hydrogenation $\propto \frac{1}{\text{Stability of alkene or crowding across pi-bond}}$

As alkynes are linear , less hindered and thermodynamically less stable than alkene, the rate of hydrogenation will be maximum in alkyne than that of alkene. So, the correct answer will be option (d).