During coupling reaction of benzene diazonium chloride and aniline, the pH of reaction medium should be approximately

Options

A. `1-2`
B. `9-10`
C. `4-5`
D. `7-8`

Answer

To determine the appropriate pH for the coupling reaction of benzene diazonium chloride and aniline, we can follow these steps:

### Step 1: Understand the Reactants
- **Benzene diazonium chloride** is a reactive compound that can undergo electrophilic substitution reactions.
- **Aniline** is an amine with a lone pair of electrons on the nitrogen atom, making it a good nucleophile.

### Step 2: Identify the Reaction Conditions
- The reaction between benzene diazonium chloride and aniline involves the nucleophilic attack of the lone pair on the nitrogen of aniline on the diazonium ion.
- For this reaction to occur effectively, the aniline must be in a state where its lone pair is available for attack.

### Step 3: Consider the pH of the Medium
- If the pH is too low (highly acidic), aniline will be protonated to form anilinium ion (C6H5NH3+), which means the lone pair on nitrogen will not be available for nucleophilic attack.
- Therefore, we need to avoid highly acidic conditions.

### Step 4: Determine the Suitable pH Range
- Mildly acidic conditions are required to keep aniline in its neutral form while still allowing some acidity to stabilize the diazonium ion.
- A pH range of approximately 4 to 5 is considered mildly acidic, which allows aniline to remain unprotonated and reactive.

### Conclusion
- The pH of the reaction medium should be approximately **4 to 5** for the coupling reaction of benzene diazonium chloride and aniline to proceed effectively.

### Final Answer
- The pH of the reaction medium should be approximately **4 to 5**.

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