Answer 1

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

\[\ce{\underset{\text{Alkane nitrile}}{R - C ≡ N +}2[H] ->[SnCl2, HCl]\underset{\text{Imine hydrochloride}}{R - HC = NH.HCl}->[H3O+]\underset{\text{Aldehyde}}{R - CHO + NH4Cl}}\]

e.g. \[\ce{\underset{\text{Ethanenitrile}}{H3C - C ≡ N}+2[H] ->[SnCl2, HCl][(reduction)]\underset{\text{Ethanimine hydrochloride}}{CH3 - HC = NH.HCl}->[H2O]+\underset{\text{Ethanal}}{CH3 - CHO} + NH4Cl}\]