Which of the following compound gives dye test ?

Options

A. Aniline
B. Methylamine
C. Diphenyl amine
D. Ethylamine

Explanation

To determine which of the following compounds gives a dye test, we need to understand the concept of the azo dye test and the types of amines involved.

### Step-by-Step Solution:

1. **Understanding the Dye Test**: The dye test, specifically the azo dye test, is a reaction that occurs with primary aromatic amines. These amines react with nitrous acid (HNO2) to form diazonium salts.

2. **Formation of Diazonium Salts**: When a primary aromatic amine reacts with nitrous acid, it forms a diazonium salt. For example, if we take aniline (C6H5NH2), it reacts with nitrous acid to form benzenediazonium chloride (C6H5N2Cl).

3. **Coupling Reaction**: The diazonium salts can undergo a coupling reaction with phenols or other aromatic compounds. This reaction leads to the formation of colored azo dyes, which are the basis of the dye test.

4. **Identifying the Compounds**:
- **Aniline (C6H5NH2)**: This is a primary aromatic amine and will give a positive dye test.
- **Methylamine (CH3NH2)**: This is an aliphatic amine and does not give a dye test.
- **Diphenylamine (C12H11N)**: This is not a primary amine; it has two phenyl groups attached to the nitrogen and does not give a dye test.
- **Ethylamine (C2H5NH2)**: This is a primary amine but is aliphatic, hence it does not give a dye test.

5. **Conclusion**: Based on the above analysis, the only compound that gives a dye test is **aniline**.

### Final Answer:
The compound that gives the dye test is **aniline**.

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