**Preparation of Phenol from Benzene Diazonium Chloride**

Phenol can be prepared from benzene diazonium chloride through a process known as the Sandmeyer reaction. This reaction involves the replacement of the diazonium group (-N2Cl) with a hydroxyl group (-OH) to form phenol.

1. **Formation of Benzene Diazonium Chloride:** Benzene diazonium chloride is commonly prepared by the diazotization reaction. In this reaction, aniline (C6H5NH2) is treated with sodium nitrite (NaNO2) and hydrochloric acid (HCl) at low temperatures.

2. **Conversion of Benzene Diazonium Chloride to Phenol:** The Sandmeyer reaction involves the treatment of benzene diazonium chloride with cuprous chloride (CuCl) in the presence of water. The reaction proceeds as follows:

- The cuprous chloride reacts with the diazonium chloride to form an intermediate, which is a copper complex of the diazonium chloride.
- This intermediate undergoes hydrolysis in the presence of water, resulting in the replacement of the diazonium group with a hydroxyl group to form phenol.

3. **Isolation of Phenol:** After the reaction is complete, the mixture is usually extracted with an organic solvent like ether or dichloromethane. The organic layer containing the phenol is separated, and any remaining impurities are removed through purification techniques such as distillation or recrystallization.

**Preparation of Benzene from Benzene Diazonium Chloride**

Benzene can be obtained from benzene diazonium chloride through a process called the Balz-Schiemann reaction. This reaction involves the replacement of the diazonium group with a fluorine atom, which is subsequently converted to a benzene ring.

1. **Formation of Benzene Diazonium Chloride:** The benzene diazonium chloride is prepared as described earlier.

2. **Balz-Schiemann Reaction:** The benzene diazonium chloride is treated with a fluorine-containing compound such as silver fluoride (AgF) or potassium fluoride (KF) in the presence of a strong acid like hydrofluoric acid (HF). The reaction proceeds as follows:

- The diazonium chloride reacts with the fluoride source to form an intermediate, which is a diazonium fluoride.
- This intermediate undergoes a rearrangement reaction, known as the Balz-Schiemann rearrangement, resulting in the replacement of the diazonium group with a fluorine atom.
- The fluorine atom is further converted to a benzene ring through elimination of hydrogen fluoride (HF) and rearrangement of the intermediate species.

3. **Isolation of Benzene:** After the reaction is complete, the mixture is usually extracted with an organic solvent. The organic layer containing benzene is separated and purified through techniques such as distillation.

**Preparation of Iodobenzene from Benzene Diazonium Chloride**

Iodobenzene can be obtained from benzene diazonium chloride through a process known as the Gattermann reaction. This reaction involves the replacement of the diazonium group with an iodine atom.

1. **Formation of Benzene Diazonium Chloride:** The benzene diazonium chloride is prepared as described earlier.

2. **Gattermann Reaction:** The benzene diazonium