How will you convert benzene into
(i) p-nitrobromobenzene
(ii) m-nitrochlorobenzene
(iii) p -nitrotoluene
(iv) acetophenone

Explanation

To convert benzene into the specified compounds, we will follow a series of reactions. Below is a step-by-step text solution for each conversion:

### (i) Conversion of Benzene to p-Nitrobromobenzene

1. **Bromination of Benzene**:
- React benzene with bromine (Br2) in the presence of a catalyst, iron(III) bromide (FeBr3).
- This will introduce a bromine atom to the benzene ring, yielding bromobenzene.

**Reaction**:
\[ \text{C}_6\text{H}_6 + \text{Br}_2 \xrightarrow{\text{FeBr}_3} \text{C}_6\text{H}_5\text{Br} \]

2. **Nitration of Bromobenzene**:
- Next, treat bromobenzene with a mixture of concentrated nitric acid (HNO3) and concentrated sulfuric acid (H2SO4).
- This will introduce a nitro group (NO2) at both the ortho and para positions.

**Reaction**:
\[ \text{C}_6\text{H}_5\text{Br} + \text{HNO}_3 + \text{H}_2\text{SO}_4 \rightarrow \text{C}_6\text{H}_4(\text{NO}_2)(\text{Br}) + \text{H}_2\text{O} \]

3. **Separation**:
- Use fractional distillation to separate the ortho and para products.
- The desired product, p-nitrobromobenzene, can be isolated.

### (ii) Conversion of Benzene to m-Nitrochlorobenzene

1. **Nitration of Benzene**:
- React benzene with a mixture of concentrated nitric acid (HNO3) and concentrated sulfuric acid (H2SO4) to introduce a nitro group.

**Reaction**:
\[ \text{C}_6\text{H}_6 + \text{HNO}_3 + \text{H}_2\text{SO}_4 \rightarrow \text{C}_6\text{H}_5(\text{NO}_2) + \text{H}_2\text{O} \]

2. **Chlorination of Nitrobenzene**:
- Treat the resulting nitrobenzene with chlorine (Cl2) in the presence of aluminum chloride (AlCl3).
- The nitro group is a deactivating group and directs the chlorine to the meta position.

**Reaction**:
\[ \text{C}_6\text{H}_5(\text{NO}_2) + \text{Cl}_2 \xrightarrow{\text{AlCl}_3} \text{C}_6\text{H}_4(\text{NO}_2)(\text{Cl}) + \text{HCl} \]

### (iii) Conversion of Benzene to p-Nitrotoluene

1. **Friedel-Crafts Alkylation**:
- React benzene with methyl chloride (CH3Cl) in the presence of aluminum chloride (AlCl3) to form toluene.

**Reaction**:
\[ \text{C}_6\text{H}_6 + \text{CH}_3\text{Cl} \xrightarrow{\text{AlCl}_3} \text{C}_6\text{H}_5\text{CH}_3 \]

2. **Nitration of Toluene**:
- Treat toluene with a mixture of concentrated nitric acid (HNO3) and concentrated sulfuric acid (H2SO4) to introduce a nitro group.
- The methyl group directs the nitro group to the para position.

**Reaction**:
\[ \text{C}_6\text{H}_5\text{CH}_3 + \text{HNO}_3 + \text{H}_2\text{SO}_4 \rightarrow \text{C}_6\text{H}_4(\text{NO}_2)(\text{CH}_3) + \text{H}_2\text{O} \]

### (iv) Conversion of Benzene to Acetophenone

1. **Friedel-Crafts Acylation**:
- React benzene with acetyl chloride (CH3COCl) in the presence of aluminum chloride (AlCl3) to form acetophenone.

**Reaction**:
\[ \text{C}_6\text{H}_6 + \text{CH}_3\text{COCl} \xrightarrow{\text{AlCl}_3} \text{C}_6\text{H}_5\text{COCH}_3 + \text{HCl} \]

2. **Final Product**:
- The product formed is acetophenone (C6H5COCH3).