Which of the following alkenes will react fastest with H ₂ under catalytic hydrogenation conditions?

Step-by-step solution

During catalytic hydrogenation, the hydrogens are transferred from the catalyst to the same side of the double bond. Evidently, smaller the number of R substituents, lesser is the steric hinderance and hence faster is the rate of hydrogenation. Thus, option (a) with two R groups on the same side of the molecule is correct.