Question

Select the reagents that reduce nitriles to primary amines: \[ \text{A. } LiAlH_4 \] \[ \text{B. } Sn+HCl \] \[ \text{C. } H_2-Ni \] \[ \text{D. } Na(Hg)/C_2H_5OH \] \[ \text{E. } Br_2/aq.\ NaOH \]

• A. A, C and D only
• B. A, B and C only
• C. B, D and E only
• D. A, D and E only

Hint:

Nitriles are reduced to primary amines by \(LiAlH_4\) or catalytic hydrogenation using \(H_2/Ni\).

Answer 1

The Correct Option is A

Step 1: Understand reduction of nitriles.
Nitriles have the functional group: \[ \ce{-C#N}. \] On reduction, nitriles give primary amines: \[ \ce{RCN -> RCH2NH2}. \]

Step 2: Check reagent A.
\[ LiAlH_4 \] is a strong reducing agent. It reduces nitriles to primary amines. So A is correct.

Step 3: Check reagent C.
Catalytic hydrogenation with: \[ H_2/Ni \] also reduces nitriles to primary amines. So C is correct.

Step 4: Check reagent D.
Reduction using sodium amalgam in ethanol can also supply hydrogen for reduction of nitriles. So D is accepted as a reducing condition for nitriles. Thus D is correct.

Step 5: Check reagent B and E.
\[ Sn+HCl \] is commonly used for reduction of nitro compounds to amines. It is not the standard reagent here for nitrile reduction. \[ Br_2/aq.\ NaOH \] is used in Hofmann bromamide reaction, not nitrile reduction. So B and E are not selected. Therefore, the correct reagents are: \[ A,\ C,\ D. \]