Fluorobenzene is prepared conveniently

Options

A. by heating benzene diazonium tetrafluoroborate
B. by treating benzene with fluorine
C. by the action of phenol with `SF_4`
D. by treating benzene with `CH_3F` in presence of anhydrous `AlCl_3`

Answer

To prepare fluorobenzene conveniently, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Fluorobenzene**:
Fluorobenzene is an aromatic compound with the formula C6H5F, where a fluorine atom is substituted for one hydrogen atom on the benzene ring.

2. **Preparation of Benzene Diazonium Salt**:
The first step is to prepare benzene diazonium salt. This can be done by treating aniline (C6H5NH2) with nitrous acid (HNO2) at low temperatures. The reaction produces benzene diazonium chloride (C6H5N2Cl).

**Hint**: Remember that diazonium salts are typically formed from primary aromatic amines.

3. **Formation of Benzene Diazonium Tetrafluoroborate**:
The benzene diazonium chloride can then be converted to benzene diazonium tetrafluoroborate by reacting it with tetrafluoroboric acid (HBF4). This forms the salt C6H5N2BF4.

**Hint**: The tetrafluoroborate ion (BF4-) is key in this step.

4. **Heating to Form Fluorobenzene**:
The benzene diazonium tetrafluoroborate is then heated. Upon heating, it decomposes to produce fluorobenzene, nitrogen gas (N2), and boron trifluoride (BF3).

**Hint**: Heating is crucial for the decomposition of diazonium salts to yield the desired aromatic compound.

5. **Final Product**:
The final product of this reaction is fluorobenzene (C6H5F), which is obtained along with nitrogen gas and boron trifluoride as by-products.

**Hint**: Always check the by-products formed during the reaction for a complete understanding of the process.

### Conclusion:
The convenient preparation of fluorobenzene is achieved by heating benzene diazonium tetrafluoroborate.

### Correct Answer:
The correct option for the preparation of fluorobenzene is **Option A: by heating benzene diazonium tetrafluoroborate**.