Rosenmund reduction

The Rosenmund reduction is a hydrogenation process in which an acyl chloride is selectively reduced to an aldehyde.

[1] The reaction, a hydrogenolysis, is catalysed by palladium on barium sulfate, which is sometimes called the Rosenmund catalyst.

Barium sulfate has a low surface area which reduces the activity of the palladium, preventing over-reduction.

If further reduction does take place, it will create a primary alcohol which would then react with the remaining acyl chloride to form an ester.

Rosenmund catalyst can be prepared by reduction of palladium(II) chloride solution in the presence of BaSO4.