SolutionsCatalytic Hydrogenation

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1. Catalytic hydrogenation

Predict the result of the catalytic hydrogenation of the following compound:

1-Cyclopentyl-1-butyne with H₂/Pd and with H₂ and Lindlar catalyst

H₂/Pd gives butylcyclopentane and the Lindlar catalyst gives (Z)-1-cyclopentyl-1-butene

2. Why does it not stop?

Why does hydrogenation with an ordinary catalyst not stop at the alkene?

Because hydrogenation of the alkene is also very exothermic and fast on the active metal. Only with a "poisoned" catalyst, such as Lindlar's, is the alkyne, which is adsorbed more strongly, hydrogenated while the alkene formed is released before reacting.

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