Question

How will you convert benzene into 

1. p-nitrobromobenzene
2. m-nitrochlorobenzene 
3. p -nitrotoluene
4. acetophenone

Answer 1

Conversions starting from benzene:

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(i) Benzene → p-Nitrobromobenzene

Step 1: Bromination of benzene
C₆H₆ + Br₂ / FeBr₃ → Bromobenzene

Step 2: Nitration of bromobenzene
Bromobenzene + conc. HNO₃ / conc. H₂SO₄ → p-Nitrobromobenzene (major) + o-isomer

(Bromine is o,p-directing; para product predominates due to less steric hindrance.)

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(ii) Benzene → m-Nitrochlorobenzene

Step 1: Nitration of benzene
C₆H₆ + conc. HNO₃ / conc. H₂SO₄ → Nitrobenzene

Step 2: Chlorination of nitrobenzene
Nitrobenzene + Cl₂ / FeCl₃ → m-Nitrochlorobenzene

(Nitro group is meta-directing.)

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(iii) Benzene → p-Nitrotoluene

Step 1: Friedel–Crafts alkylation
C₆H₆ + CH₃Cl / AlCl₃ → Toluene

Step 2: Nitration of toluene
Toluene + conc. HNO₃ / conc. H₂SO₄ → p-Nitrotoluene (major) + o-isomer

(Methyl group is o,p-directing; para product predominates.)

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(iv) Benzene → Acetophenone

Step: Friedel–Crafts acylation

C₆H₆ + CH₃COCl / AlCl₃ → Acetophenone

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Final Summary:

• Benzene → Bromobenzene → p-Nitrobromobenzene
• Benzene → Nitrobenzene → m-Nitrochlorobenzene
• Benzene → Toluene → p-Nitrotoluene
• Benzene → Acetophenone (Friedel–Crafts acylation)