Write short note on Stephens reduction.

Explanation

When an ethereal solution of an alkyl or aryl cyanide is reduced with HCI (aq) and `SnCl_(2)` at room temperature, Acetald imine hydrochloride is precipitated. This upon hydrolysis with boiling water gives aldehyde. For example,
`SnCl_(2)+2HClrarrSnCl_(4)+2[H]`
`underset("Methylcyanide")(CH_(3)-C-=N)+2[H]+HClunderset(290-295^(@)K)overset("Ether")rarrunderset("Acetaldimine hydrochloride")(CH_(3)CH=NH.HCl)`
`underset("Boil")overset(H_(2)O)rarrunderset("Acetaldehyde")(CH_(3)CHO)+NH_(4)Cl`