Predict the major product of the hydrogenation of 1-hexyne with a Lindlar catalyst.

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Multiple Choice

Predict the major product of the hydrogenation of 1-hexyne with a Lindlar catalyst.

Lindlar catalyst makes hydrogenation stop at the alkene stage and adds hydrogen to the same face of the triple bond (syn addition), so you get a cis-alkene rather than a trans one or a fully reduced alkane. For 1-hexyne, the triple bond is between the first two carbons. Hydrogenation with this catalyst adds H2 across that bond on the same side, converting it to a double bond and producing cis-hex-1-ene. The catalyst is poisoned to prevent further hydrogenation to hexane, and forming a ketone would require a different type of reaction entirely. So the major product is cis-hexene.

Lindlar catalyst makes hydrogenation stop at the alkene stage and adds hydrogen to the same face of the triple bond (syn addition), so you get a cis-alkene rather than a trans one or a fully reduced alkane.

For 1-hexyne, the triple bond is between the first two carbons. Hydrogenation with this catalyst adds H2 across that bond on the same side, converting it to a double bond and producing cis-hex-1-ene. The catalyst is poisoned to prevent further hydrogenation to hexane, and forming a ketone would require a different type of reaction entirely.

So the major product is cis-hexene.

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