organic chemistry - Hydrogenation stereochemistry-Pd,Pt, Ni catalysts

When my textbook talks about hydrogenation using Pt, Pd or Ni heterogeneous catalysts, it never mentions if it is anti or syn addition. It simply jumps on to say that for alkynes, NiB2 (P-2) catalysts and Lindlar's catalysts are syn hydrogenation. Can someone tell me if using Pt gives syn or anti for alkynes?

Answer

Using any transition metal catalyst (Pt, Pd, Ni) for hydrogenation of alkynes results in syn hydrogenation to not alkenes but alkanes. Using Lindlar's catalyst results in syn hydrogenation of an alkyne to an alkene.

In the case of sodium metal (not a transition metal) in ammonia, hydrogenation of alkynes results in a trans alkene.