(i) Stephen’s reaction:
Cyanides are reduced to aldehydes by treating their ethereal solution with stannous chloride and hydrogen chloride gas at room temperature. Imine hydrochloride is initially formed which upon boiling with water gives aldehyde. This reduction is called Stephen’s reaction.

(ii) Rosenmund’s reduction:
Aliphatic as well as’ aromatic aldehydes can be prepared by the reduction of acid chlorides with H2 in the presence of palladium (Pd) deposited over barium sulphate along with a small amount of sulphur or quinoline. This mixture is called Lindlar’s catalyst, Both sulphur and quinoline poison palladium and check its ability to reduce aldehyde into alcohol. This reaction is called Rosenmund’s reduction.
