Illustrated Glossary of Organic Chemistry

Lindlar catalyst: A poisoned catalyst consisting of palladium, calcium carbonate, lead (II) acetate, and quinoline. Particularly useful for catalytic hydrogenation of an alkyne to the corresponding cis alkene without over-reduction to the corresponding alkane.

Components of the Lindlar catalyst.

	H2 Lindlar catalyst		H2 Lindlar catalyst
1-Phenylpropyne An alkyne Starting material		Cis-1-phenylpropene An alkene Reaction product		1-Phenylpropane Not formed

In this catalytic hydrogenation reaction, 1-phenylpropyne is reduced using the Lindlar catalyst. The alkyne is reduced to the corresponding cis alkene, but not further reduced to the alkane. Had the catalyst been Pd by itself (without a poison), the alkene could not be isolated because it would be quickly reduced to the corresponding alkane.