Which of the following compounds will give methyl orange by the reaction with diazonium salt of sodium p - amino benzene sulphonate?

Options

A. Aniline
B. N, N - Dimethyl aniline
C. m - nitro aniline
D. m - bromophenol

Answer

To solve the problem of which compound will react with the diazonium salt of sodium p-amino benzene sulphonate to form methyl orange, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Diazonium Salt**:
The diazonium salt in question is derived from sodium p-amino benzene sulphonate. The structure of this compound includes a benzene ring with a sulfonate group (SO3Na) and an amino group (NH2) in the para position. When treated with NaNO2 in the presence of HCl, it forms the diazonium salt.

2. **Structure of Methyl Orange**:
Methyl orange is an azo dye, which consists of two aromatic rings connected by a nitrogen-nitrogen (N=N) bond. The structure includes a sulfonate group (SO3Na) and two methyl groups (–CH3) attached to one of the aromatic rings.

3. **Determine the Required Compound**:
To form methyl orange, we need a compound that can provide the second aromatic ring with the necessary substituents. The required compound must be capable of undergoing a coupling reaction with the diazonium salt.

4. **Identify the Correct Compound**:
The compound that fits this requirement is N,N-dimethylaniline. This compound has two methyl groups attached to the nitrogen atom and can effectively couple with the diazonium salt to form the azo compound that constitutes methyl orange.

5. **Reaction Mechanism**:
When N,N-dimethylaniline reacts with the diazonium salt, it undergoes an electrophilic aromatic substitution, where the diazonium group (N2+) reacts with the aromatic ring of N,N-dimethylaniline, leading to the formation of methyl orange.

6. **Conclusion**:
The correct answer to the question is that N,N-dimethylaniline will react with the diazonium salt of sodium p-amino benzene sulphonate to produce methyl orange.

### Final Answer:
The compound that will give methyl orange by the reaction with diazonium salt of sodium p-amino benzene sulphonate is **N,N-dimethylaniline**.