Which of the following is the correct sequential method to convert benzene to 3-nitrobenzoic acid

Options

A. alkaline` KMnO_4, conc H_2SO_4//HNO_3,CH_3Cl+FeCl_3`
B. `CH_3Cl+FeCl_3,` alkaline`KMnO_4, conc H_2SO_4//HNO_3`
C. alkaline` KMnO_4,CH_3Cl+FeCl_3,conc H_2SO_4//HNO_3`
D. `conc H_2SO_4//HNO_3,CH_3Cl+FeCl_3`, alkaline `KMnO_4`

Answer

To convert benzene to 3-nitrobenzoic acid, we can follow a systematic approach involving three main steps: Friedel-Crafts alkylation, oxidation, and nitration. Here is the step-by-step solution:

### Step 1: Friedel-Crafts Alkylation
1. **React benzene with methyl chloride (CH₃Cl)** in the presence of a Lewis acid catalyst such as **FeCl₃**. This will introduce a methyl group (–CH₃) onto the benzene ring, resulting in toluene (methylbenzene).

**Reaction:**
\[ \text{Benzene} + \text{CH}_3\text{Cl} \xrightarrow{\text{FeCl}_3} \text{Toluene} \]

### Step 2: Oxidation to Benzoic Acid
2. **Oxidize toluene to benzoic acid** using alkaline potassium permanganate (KMnO₄). This reaction will convert the methyl group into a carboxylic acid group (–COOH), yielding benzoic acid.

**Reaction:**
\[ \text{Toluene} \xrightarrow{\text{KMnO}_4/\text{OH}^-} \text{Benzoic Acid} \]

### Step 3: Nitration to 3-Nitrobenzoic Acid
3. **Nitrate benzoic acid** using a nitrating mixture (HNO₃ and H₂SO₄). The nitro group (–NO₂) will be introduced at the meta position relative to the carboxylic acid group due to its electron-withdrawing nature, resulting in 3-nitrobenzoic acid.

**Reaction:**
\[ \text{Benzoic Acid} \xrightarrow{\text{HNO}_3/\text{H}_2\text{SO}_4} \text{3-Nitrobenzoic Acid} \]

### Summary of Steps
1. Friedel-Crafts alkylation of benzene with methyl chloride to form toluene.
2. Oxidation of toluene to benzoic acid using alkaline KMnO₄.
3. Nitration of benzoic acid to form 3-nitrobenzoic acid using a nitrating mixture.

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