Question

Acetonitrile may be prepared by heating the following reactants :

• A. Ethyl chloride with alcoholic KCN
• B. Ethyl chloride with alcoholic AgCN
• C. Methyl chloride with alcoholic KCN
• D. Methyl chloride with alcoholic AgCN

Hint:

KCN is ionic and provides $CN^-$ ions leading to Cyanides (C-linkage). AgCN is covalent and attacks via Nitrogen leading to Isocyanides (N-linkage). Always count the total carbons in the final nitrile name.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Acetonitrile is methyl cyanide ($CH_3CN$).
It contains two carbon atoms. The synthesis involves increasing the carbon chain length starting from an alkyl halide.
Step 2: Key Formula or Approach:
Reaction of alkyl halides with potassium cyanide ($KCN$) yields alkyl cyanides (nitriles), whereas reaction with silver cyanide ($AgCN$) yields alkyl isocyanides.
Step 3: Detailed Explanation:
To obtain $CH_3CN$ (2 carbons), we must start with an alkyl halide containing 1 carbon atom, which is methyl chloride ($CH_3Cl$).
The reaction is:
\[ CH_3Cl + KCN(\text{alc.}) \xrightarrow{\Delta} CH_3CN + KCl \]
If we used ethyl chloride ($C_2H_5Cl$), the product would be propionitrile ($C_2H_5CN$).
If we used $AgCN$, the product would be methyl isocyanide ($CH_3NC$).
Step 4: Final Answer:
Acetonitrile is prepared by heating methyl chloride with alcoholic KCN.