Question

Explain Rosenmond’s reduction of benzoyl chloride.

Answer 1

Rosenmund’s reduction is a hydrogenation process in which acid chloride is selectively reduced to aldehydes.

Complete step by step answer:
Acyl chlorides can be reduced into aldehydes with hydrogen in boiling xylene using palladium or platinum as catalyst supported on barium sulphate. This reaction is called Rosenmund’s reduction.
For example:

Similarly

The function of $BaS{O_4}$is to poison the catalyst at the aldehyde stage. The catalyst is also poisoned to small extent by sulphur compounds to prevent further reaction of aldehyde to $1^\circ$ alcohols. Generally, a small amount of quinoline and sulphur is also added.

Note:
Rosenmund’s reduction is only for the preparation of aldehydes but ketones cannot be prepared by this method.
Acid chlorides are readily reduced to aldehydes by weaker reducing agents, like lithium tri – tertiary butoxy aluminium hydride.