Hydrogenation of alkynes and alkenes

[tandoorichicken]

Hello.

I have a question about catalytic hydrogenation reagents. I know that you can perform syn hydrogenation of alkenes with H2 and Pd catalyst, and the same goes for alkynes except for the addition of quinoline (and CaCO3 doped Pd catalyst).

I was wondering if there is a reaction with alkynes and just H2 and Pd catalyst?

 

[tandoorichicken]

got it. quinoline stops reduction at the alkene stage. reacting alkyne with direct H2 and Pd gives a tetrahydrogenated alkane.

 

[Blueshift5]

Hello, thank you for your question. Yes, it is possible to perform hydrogenation of alkynes with just H2 and a Pd catalyst. This reaction is known as semi-hydrogenation, as it only adds one hydrogen atom to the triple bond of the alkyne. However, this reaction is not as efficient as using a quinoline or other additives, as it can lead to over-reduction and formation of alkanes. Additionally, the use of additives can help control the stereochemistry of the product. Overall, the use of quinoline or other additives is preferred for selective and efficient hydrogenation of alkynes.