Alkynes: addition of H2 gas and Lindlar catalyst

Alkynes: addition of Hydrogen gas (H2)

Performing a catalytic reduction on an alkyn will result in giving an alkane. The alkene intermediate will be formed in the process, but will immediately react into an alkane. The end result is just the formed alkane, without stacking of the alkene intermediate.

The Lindlar catalyst

In theory this is a "poisoned or defected" catalyst. If you use a normal catalyst you will get the above effect with your alkyne.

The Lindlar catalyst contains Palladium combined with Calcium-carbonate and treated with Lead.

Palladium is the actual catalyst, the calcium carbonate is the carrier of the substance and the lead is the poisonous compound.

Using the Lindlar catalyst instead of another catalyst together with Hydrogen gas, will lead into forming the cis-alkene intermediate instead of the forming of the corresponding alkane.

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