In Rosenmund Reaction, acyl chloride is hydrogenated to get reduced into aldehyde and palladium-barium sulphate is used as catalyst. It is a reduction reaction involves addition of hydrogen.
Rosenmund Reaction can be written as follows –
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Acyl Chloride Alkyl Aldehyde
R can be an alkyl or aryl group in the above reaction.
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As we have discussed above, Palladium on barium sulphate is called rosenmund catalyst. Use of palladium induces the reduction process while use of barium sulphate reduces the activity of palladium as barium sulphate has low surface area, thus prevents the over reduction. Over reduction should be stopped for the desired product which is aldehyde in this reaction. If over reduction takes place, then aldehyde converts into alcohol which would the react with remaining acyl chloride and form ester. To prevent further hydrogenation, catalyst is mixed with poison.
Rosenmund catalyst is prepared by reduction of palladium (II) chloride solution in the presence of barium sulphate.
1. Preparation of Acyl Chloride From an Acid –
(Image to be added soon) SOCl2 or PCl3or PCl5→ (Image to be added soon)
Carboxylic Acid Acyl Chloride
2. Preparation of Aldehyde –
We use a poisoned rosenmund catalyst to get the desired product which is aldehyde. So, we use palladium with barium sulphate.
(Image to be added soon) Pd-BaSO4 (partial hydrogenation)→ (Image to be added soon) + HCl
If we don’t use poisoned palladium then reaction will take place as follows –
(Image to be added soon) Pd(non poisoned catalyst)→ (Image to be added soon) Pd (Image to be added soon) (Image to be added soon)
In this condition we get ester in place of aldehyde.
1.Rosenmund reduction reaction is used for the production of aldehydes.
2. It is used for the production of saturated fatty aldehydes.
3. It is used for the production of alkyl or aryl aldehydes.
Limitation of Rosenmund Reaction
We can prepare many aldehydes by Rosenmund Reduction Reactions but formaldehydes cannot be prepared. As formyl chloride is unstable at room temperature.
Rosenmund reduction reaction is one of the important name reactions of CBSE Class 12 Chemistry for your final board examinations. You need to practice twice all the name reactions to score high marks in the examination. We at Vedantu have provided “Important Chemical Reactions of Class 12 Chemistry” page also for you so that you can score maximum. You can also find similar articles on other name reactions such as diazotization reaction, hofmann elimination reaction, Friedel crafts reaction etc. at Vedantu.