TheRosenmund reductionis a hydrogenation process in which an acylchloride is selectively reduced to an aldehyde. The reaction was named after karl roseemund who first reported it in 1918.

This reaction, a hydrogenelisis , is catalysed by palladium on barium sulphate, which is sometimes called theRosenmund 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 thioquianthrene 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.Rosenmund catalyst can be prepared by reduction of palladium(II) chloride solution in the presence of BaSO4. Typical reducing agent is formaldehyde.

Rosenmund Reduction is an organic chemical reaction in whichthe acid chloride is converted to aldehydesby using hydrogen gas passed over palladium-on-carbon poisoned with barium sulfate. This reaction is named after a German chemistKarl Wilhelm Rosenmund.

In order to prevent further hydrogenation, catalyst is mixed with a poison. Catalytic hydrogenation of acid chlorides allows the formation of aldehydes

Summary:

The Pd catalyst must be poisoned, for example with BaSO4, because the untreated catalyst is too reactive and will give some overreduction. Some of the side products can be avoided if the reaction is conducted in strictly anhydrous solvents.