Rosenmund reduction

The Rosenmund reduction is a hydrogenation process in which an acyl chloride is selectively reduced to an aldehyde. The reaction was named after Karl Wilhelm Rosenmund who first reported it in 1918.

The Rosenmund reduction

The reaction 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. However for certain reactive acyl chlorides the activity must be reduced further, by the addition of a poison. Originally this was thioquinanthrene although thiourea has also been used. Deactivation is required because the system must reduce the acyl chloride but not the subsequent aldehyde. 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.

See also

• Lindlar catalyst - Palladium on calcium carbonate with added catalytic poison, similar to the Rosenmund catalyst
• Rosenmund–von Braun reaction - Another reaction named after Karl Wilhelm Rosenmund in which an aryl halide is converted into an aryl nitrile
• Grundmann aldehyde synthesis - Also reduces an acyl halide to an aldehyde, via the use of diazomethane
• Diisobutylaluminium hydride (DIBALH) can also reduce acid chlorides to aldehydes.
• Gattermann–Koch reaction - A reaction which produces an aldehyde via an intermediate acyl chloride

Further reading

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