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Organic conversion

Benzene to aniline

2 steps: substitution, then reduction

Class 11, Chapter 9 Hydrocarbons; Class 12, Chapter 9 Amines

  1. BenzeneC₆H₆Arene
  2. Step 1

    conc. HNO₃ + conc. H₂SO₄

    323 to 333 K

    i

    Nitration: the nitronium ion is the electrophile; keep below 333 K to avoid dinitration.

    O−N+O
    NitrobenzeneC₆H₅NO₂Nitro compound
  3. Step 2

    Sn + conc. HCl

    i

    Metal in acid reduces the nitro group; the amine comes out as its salt, so add NaOH at the end.

    Also written: Fe + HCl; H₂, Pd (in ethanol)

    NH2
    AnilineC₆H₅NH₂Amine

Exam answer

  1. Step 1: Benzene to nitrobenzene: conc. HNO₃ + conc. H₂SO₄, 323 to 333 K.
  2. Step 2: Nitrobenzene to aniline: Sn + conc. HCl.
Alternative routes (3)
  • Benzene → Toluene → Benzoic acid → Benzamide → Aniline
    1. Benzene to toluene: CH₃Cl, anhydrous AlCl₃.
    2. Toluene to benzoic acid: KMnO₄, KOH, heat; then H₃O⁺.
    3. Benzoic acid to benzamide: NH₃, then heat.
    4. Benzamide to aniline: Br₂ + NaOH(aq).
  • Benzene → Ethylbenzene → Benzoic acid → Benzamide → Aniline
    1. Benzene to ethylbenzene: CH₃CH₂Cl, anhydrous AlCl₃.
    2. Ethylbenzene to benzoic acid: KMnO₄, KOH, heat; then H₃O⁺.
    3. Benzoic acid to benzamide: NH₃, then heat.
    4. Benzamide to aniline: Br₂ + NaOH(aq).
  • Benzene → Benzaldehyde → Benzoic acid → Benzamide → Aniline
    1. Benzene to benzaldehyde: CO + HCl, anhydrous AlCl₃ / CuCl.
    2. Benzaldehyde to benzoic acid: KMnO₄, KOH, heat; then H₃O⁺.
    3. Benzoic acid to benzamide: NH₃, then heat.
    4. Benzamide to aniline: Br₂ + NaOH(aq).
Why these reagents

Reagent and reason, step by step

  • Step 1: Benzene to nitrobenzene: conc. HNO₃ + conc. H₂SO₄, 323 to 333 K Nitration: the nitronium ion is the electrophile; keep below 333 K to avoid dinitration.
  • Step 2: Nitrobenzene to aniline: Sn + conc. HCl Metal in acid reduces the nitro group; the amine comes out as its salt, so add NaOH at the end.
Questions

Benzene to aniline: quick answers

How many steps does it take to convert benzene to aniline?

2 steps: Benzene, then nitrobenzene, then aniline.

Which named reaction is used to convert benzene to aniline?

None of the steps has a name. They are substitution and reduction, so write the reagent and the condition for each step.

What is the reagent for step 1 of benzene to aniline?

Benzene to nitrobenzene: conc. HNO₃ + conc. H₂SO₄, 323 to 333 K. Nitration: the nitronium ion is the electrophile; keep below 333 K to avoid dinitration.

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