Question

What is formed when an alkyl cyanide reacts with sodium in ether?

• A. Primary amine
• B. Secondary amine
• C. Alkene
• D. Alcohol

Hint:

Remember the important conversion: \[ R-C \equiv N \xrightarrow[\text{Reduction}]{} R-CH_2NH_2 \] Thus:
• Nitrile \(\rightarrow\) Primary amine
• Number of carbon atoms increases by one compared to alkyl halide used in cyanide preparation.

Answer 1

The Correct Option is A

Concept: Alkyl cyanides (also called nitriles) contain the functional group: \[ -C \equiv N \] When nitriles undergo reduction, the cyanide group is converted into an amino group \((-NH_2)\). Reduction of nitriles can be carried out using reducing agents such as:
• Sodium in ether
• Lithium aluminium hydride \((LiAlH_4)\)
• Hydrogen gas in presence of catalysts like Ni or Pt The reduction converts: \[ R-C \equiv N \longrightarrow R-CH_2NH_2 \] The product formed is a primary amine.

Step 1: Understanding the structure of alkyl cyanide.
An alkyl cyanide has the general formula: \[ R-C \equiv N \] where:
• \(R\) represents an alkyl group.
• \(-C \equiv N\) is the nitrile functional group.

Step 2: Reduction of nitrile group.
During reduction, the carbon-nitrogen triple bond gains hydrogen atoms and gets converted into: \[ -CH_2NH_2 \] Thus: \[ R-C \equiv N \xrightarrow[\text{ether}]{Na} R-CH_2NH_2 \]

Step 3: Identifying the product formed.
The group \(-NH_2\) attached to one carbon atom represents a primary amine. For example: \[ CH_3CN \longrightarrow CH_3CH_2NH_2 \] Ethyl cyanide gives ethylamine after reduction.

Step 4: Evaluating the options.

• Primary amine: Correct, nitriles reduce to primary amines.
• Secondary amine: Incorrect, no second alkyl group is attached to nitrogen.
• Alkene: Incorrect, reduction does not form double bonds here.
• Alcohol: Incorrect, nitriles do not reduce into alcohols under these conditions.

Step 5: Final conclusion.
Therefore, alkyl cyanides on reduction with sodium in ether form: \[ \boxed{\text{Primary amine}} \] Hence, the correct option is: \[ \boxed{(1)\ \text{Primary amine}} \]