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.
Top Questions on Amines
- Identify correct statements: (A) Primary amines do not give diazonium salts when treated with \({NaNO}_2\) in acidic condition.
(B) Aliphatic and aromatic primary amines on heating with \({CHCl}_3\) and ethanolic \({KOH}\) form carbylamines.
(C) Secondary and tertiary amines also give carbylamine test.
(D) Benzenesulfonyl chloride is known as Hinsberg’s reagent.
(E) Tertiary amines react with benzenesulfonyl chloride very easily.
Choose the correct answer from the options given below: Amines are usually formed from amides, imides, halides, nitro compounds, etc. They exhibit hydrogen bonding which influences their physical properties. In alkyl amines, a combination of electron releasing, steric and H-bonding factors influence the stability of the substituted ammonium cations in protic polar solvents and thus affect the basic nature of amines. Alkyl amines are found to be stronger bases than ammonia. Amines being basic in nature, react with acids to form salts. Aryldiazonium salts, undergo replacement of the diazonium group with a variety of nucleophiles to produce aryl halides, cyanides, phenols and arenes.
How can you convert the following:
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