Stephen’s Reduction

An alkyl or aryl cyanide dissolved in ether is reduced with stannous chloride and HCl to give aliphatic or aromatic aldehydes. The reaction proceeds by the formation of aldimine hydrochloride (present as stannichloride), which are not stable and hydrolyse to give aldehydes.

Mechanism of stephens Reactions

Following is the mechanism of Stephens reaction. 

1. Gaseous hydrogen chloride(HCl) is added to the given nitrile, which reacts to provide its corresponding salt.
2. A single electron transfer from the tin(II) chloride reduces this salt. On further reduction with HCl, it forms tin (IV) tetrachloride and amine.
3. The salt obtained in step 2 precipitates quickly after as aldimine tin chloride.
4. The hydrolysis of aldimine tin chloride yields an amide. 
5. The required aldehyde is formed from this amide. During this ammonium chloride is also formed.

Example of Stephen’s Reduction

List of Name Reaction of Organic Chemistry consist of detail Reaction Mechanism of all name reactions of Organic Chemistry.

Key Points

1. Substitutes that can improve the electron density will improve the formation of the aldimine tin chloride.
2. Electron withdrawing substituents also promote the formation of amide chloride. 

Applications

Stephens reduction reaction is used in the preparation of aldehydes by using alkyl cyanides.

Also Check

• Grignard Reagent
• Kolbes Reaction
• Jones Reagent