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 \(CH_3CN\) (ethanenitrile).
Alkyl halides react with cyanide salts to form nitriles via nucleophilic substitution (\(S_N2\)).
Step 3: Detailed Explanation:
When Methyl chloride (\(CH_3Cl\)) reacts with alcoholic Potassium Cyanide (\(KCN\)), the \(CN^-\) ion (an ambident nucleophile) attacks the methyl group.
Since \(KCN\) is ionic, the nucleophilic attack occurs through the Carbon atom, leading to the formation of a nitrile.
Reaction:
\[ CH_3Cl + KCN(alc.) \xrightarrow{\Delta} CH_3CN + KCl \]
If \(AgCN\) were used, the attack would occur through Nitrogen, forming an isocyanide (\(CH_3NC\)).
Step 4: Final Answer:
Acetonitrile is prepared by heating Methyl chloride with alcoholic \(KCN\).