The catalytic hydrogenation of benzene produces

Analyze the question: It asks for the product when benzene (C₆H₆) reacts with hydrogen in the presence of a catalyst.

Concept: Benzene is an aromatic compound with a ring of six carbon atoms and delocalized electrons. Under normal conditions it resists addition reactions, but with a nickel catalyst at about 150-200°C (and high pressure), it adds hydrogen. The ring stays intact, and the delocalized double bonds become single bonds.

Solution:

C₆H₆ + 3H₂ → C₆H₁₂ (Ni catalyst, heat, pressure)

• Benzene has 6 carbons and 6 hydrogens, with three C=C double bonds (in the Kekulé representation).
• Each double bond takes up one H₂ molecule, so 3 H₂ molecules are added.
• The product has 6 carbons and 12 hydrogens, arranged in a ring. This is cyclohexane, a saturated cyclic alkane.

Checking the options:

• A. Hexane (C₆H₁₄) is an open-chain alkane. The ring would have to break, which does not happen here.
• B. Margarine comes from the hydrogenation of vegetable oils (unsaturated fats), not benzene.
• C. Hexene (C₆H₁₂) is an open-chain alkene. It has the same formula as cyclohexane but is a different structure, and the ring does not open.
• D. Cyclohexane (C₆H₁₂) is correct.

Answer: D. cyclohexane

Exam tip: Remember that "benzene + H₂ with Ni" gives cyclohexane (the ring stays closed, C₆H₁₂). Also note that hydrogenation of oils gives margarine, while hydrogenation of benzene gives cyclohexane. JAMB likes to include both as options to test whether you can tell them apart.