Question

Carbylamine is obtained when aniline is

• A. heated with Con. H\(_2\)SO\(_4\)
• B. treated with NaNO\(_2\) HCl
• C. heated with CHCl\(_3\) and ethanolic KOH
• D. treated with CHCl\(_3\) and HCl
• E. treated with HCl

Hint:

The carbylamine test is given only by primary aliphatic and aromatic amines. Secondary and tertiary amines do not give this test.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
The question asks about the synthesis of a carbylamine (also known as an isocyanide or isonitrile). This synthesis is a specific named reaction known as the Carbylamine reaction or Hofmann's isocyanide test.
Step 2: Detailed Explanation:
The Carbylamine reaction is a chemical test for the detection of primary amines. In this reaction, a primary amine (aliphatic or aromatic) is heated with chloroform (CHCl\(_3\)) and a strong base, typically ethanolic or alcoholic potassium hydroxide (KOH). This reaction produces an isocyanide, which is characterized by an extremely unpleasant or foul smell.
The reaction for aniline (a primary aromatic amine) is: \[ \text{C}_6\text{H}_5\text{NH}_2 + \text{CHCl}_3 + 3\text{KOH (alcoholic)} \xrightarrow{\Delta} \text{C}_6\text{H}_5\text{NC} + 3\text{KCl} + 3\text{H}_2\text{O} \] The product, C\(_6\)H\(_5\)NC, is phenyl isocyanide, which is a carbylamine. The reaction proceeds via the formation of a dichlorocarbene (:CCl\(_2\)) intermediate from the reaction of CHCl\(_3\) and KOH.
Secondary and tertiary amines do not give this reaction, making it a reliable test for the primary amino group.
Step 3: Final Answer:
Carbylamine (phenyl isocyanide) is obtained when aniline is heated with chloroform and ethanolic KOH. This corresponds to option (C).