Question

Write Stephen reaction for the preparation of aldehyde.

Answer 1

Nitriles are reduced to imine hydrochloride by stannous chloride in the presence of hydrochloric acid which on acid hydrolysis gives corresponding aldehydes. This reaction is called Stephen reaction.

$$\underset{(\mathrm{Nitrile})}{\mathrm{R}-\mathrm{C}\equiv \mathrm{N}}+2[\mathrm{H}]\stackrel{\mathrm{SnCl}{\phantom{A}}_2,\mathrm{HCl}}{\to }\underset{(\mathrm{lmmine}\mathrm{hydrochloride})}{\mathrm{R}-\mathrm{C}\equiv \mathrm{N}\cdot \mathrm{HCl}}\underset{\mathrm{H}{\phantom{A}}_3\mathrm{O}{\phantom{A}}^{+}}{\overset{\mathrm{H}{\phantom{A}}^{+}}{\to }}\underset{(\mathrm{Aldehyde})}{\mathrm{R}-\mathrm{CHO}}+\mathrm{NH}{\phantom{A}}_4\mathrm{Cl}$$