Which of the following amine(s) show(s) positive carbamylamine test?
Which of the following amine(s) show(s) positive carbamylamine test?
Show Hint
- A and E Only
- C Only
- A and C Only
- B, C and D Only
The Correct Option is C
Approach Solution - 1
The carbamylamine test is used to detect primary amines. It results in the formation of an isocyanide (carbamylamine).
Option A \( \text{NH}_2 \) (Phenylamine) is a primary amine and will give a positive result.
Option B \( \text{(CH}_3)_2\text{NH} \) (Dimethylamine) is a secondary amine and does not give a positive result.
Option C \( \text{CH}_3\text{NH}_2 \) (Methylamine) is a primary amine and will give a positive result.
Option D \( \text{(CH}_3)_3\text{N} \) (Trimethylamine) is a tertiary amine and does not give a positive result.
Option E \( \text{H}\text{NCH}_3 \) (Methylamine attached to a benzene ring) is a primary amine and will give a positive result.
Thus, the correct options are A and C.
Approach Solution -2
The carbamylamine test is used to detect the presence of primary amines (1° amines).
Reaction Mechanism:
- When a primary amine (either aliphatic or aromatic) is treated with chloroform (CHCl₃) in the presence of an alkali (such as potassium hydroxide, KOH), it undergoes a reaction to form an isocyanate.
- This is a characteristic test for primary amines, as secondary and tertiary amines do not undergo this reaction.
The reaction can be represented as follows:
\[ \text{RNH}_2 \xrightarrow{\text{CHCl}_3 + \text{KOH}} \text{RNC} \] Where:
- RNH₂ represents the primary amine group.
- CHCl₃ is chloroform, which reacts with the amine in the presence of an alkaline medium.
- KOH is potassium hydroxide, which is used to generate the basic condition needed for the reaction.
- RNC represents the isocyanate product formed.
Note:
- The reaction is specific to primary amines (1° amines), both aliphatic and aromatic. Secondary (2°) and tertiary (3°) amines do not respond to this test. Thus, if an isocyanate (RNC) is formed, it indicates the presence of a primary amine.
This test is useful in organic chemistry to distinguish primary amines from other types of amines.
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