Q.Which product is obtained when methyl cyanide is reduced by sodium and ethyl alcohol?

Mendius Reduction: From Nitrile to Primary Amine

Imagine you have a nitrile — a molecule with a carbon triple-bonded to a nitrogen ($-C \equiv N$). That triple bond is very tight and stable. Your goal is to turn it into a primary amine ($-CH_2NH_2$), which is a much more reactive, useful functional group. How do you break that triple bond and add hydrogen atoms in a controlled way?

That's exactly what Mendius reduction does. It's a brute-force hydrogenation: you smash four hydrogen atoms onto the nitrile group, breaking the triple bond and building a $CH_2$—$NH_2$ unit.

The Intuition

Think of the triple bond as a very strong rope. To turn it into a single bond, you need to cut two of the three connections and then attach hydrogen atoms to the loose ends. The carbon end gets two hydrogens (becoming $CH_2$), and the nitrogen end gets two hydrogens (becoming $NH_2$). The net change is:

The "4[H]" is shorthand for four hydrogen atoms being added. In practice, these come from either:

• Sodium metal in alcohol (like ethanol): sodium reacts with alcohol to generate hydrogen in situ, which then attacks the nitrile.
• Catalytic hydrogenation (H₂ gas with a catalyst like Ni, Pt, or Pd): the hydrogen gas is adsorbed onto the catalyst surface and delivered to the nitrile.

The Precise Statement

Mendius reduction is the conversion of a nitrile to a primary amine by the addition of four hydrogen atoms, using either sodium in alcohol or catalytic hydrogenation.

Key Details for Exams

• Reagents: Na + C₂H₅OH (or any alcohol) OR H₂ + Ni/Pt/Pd.
• Product: Always a primary amine — the $NH_2$ group is attached to a carbon that originally was the nitrile carbon.
• Mechanism (simplified): The reaction proceeds through an imine intermediate ($R-CH=NH$), which is then further reduced to the amine. You don't need to draw the mechanism in most exams, but knowing the intermediate exists helps understand why you get the primary amine and not something else.

Example

Convert butyronitrile to butylamine: …