See image — Hydrocarbons Chemistry Question

💡 Solution & Explanation

Concept: Hydrogenation of olefins (alkenes) refers to the addition of molecular hydrogen (H2) across a carbon-carbon double bond to give an alkane. This process requires a suitable hydrogen source and typically a catalyst. Step 1: Understand what hydrogenation requires. True catalytic hydrogenation of olefins requires molecular hydrogen (H2) in the presence of a heterogeneous or homogeneous catalyst. The catalyst activates H2 and facilitates its addition to the double bond. Step 2: Evaluate each option. - Option (a) Zinc and HCl: This combination generates nascent hydrogen (Zn + HCl → ZnCl2 + [H]), but nascent hydrogen in this context is not the standard reagent for hydrogenation of simple olefins; this is more associated with reduction of specific functional groups. - Option (b) Nascent hydrogen: Nascent hydrogen (atomic hydrogen) can reduce certain functional groups but is not the standard, efficient reagent for hydrogenation of olefins in a controlled manner. - Option (c) Raney Ni and H (i.e., Raney Nickel with H2): Raney Nickel is a finely divided nickel catalyst that is widely used for the catalytic hydrogenation of olefins. In the presence of hydrogen gas (H2), Raney Ni efficiently catalyzes the addition of H2 across the C=C double bond to produce the corresponding alkane. This is the classic and well-established method for hydrogenating olefins. - Option (d) Lithium hydride (LiH) in ether: LiH is an ionic hydride and a strong base/reducing agent, but it does not hydrogenate olefins. It lacks the ability to add H2 across a C=C double bond under normal conditions. Step 3: Conclusion. Raney Nickel with hydrogen gas (H2) is the standard reagent system for catalytic hydrogenation of olefins, making option (c) correct. Therefore, the correct answer is C.