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Organic conversion

Benzene to toluene

1 step: Friedel-Crafts alkylation

Class 11, Chapter 9 Hydrocarbons

  1. BenzeneC₆H₆Arene
  2. Step 1

    CH₃Cl, anhydrous AlCl₃

    Friedel-Crafts alkylation
    i

    Friedel-Crafts alkylation; the product is more reactive than benzene, so polyalkylation occurs unless benzene is in excess.

    TolueneC₆H₅CH₃Arene

Exam answer

  1. Step 1: Benzene to toluene: CH₃Cl, anhydrous AlCl₃.
Alternative routes (3)
  • Benzene → Chlorobenzene → Toluene
    1. Benzene to chlorobenzene: Cl₂, anhydrous FeCl₃.
    2. Chlorobenzene to toluene: CH₃Cl, Na, dry ether.
  • Benzene → Bromobenzene → Toluene
    1. Benzene to bromobenzene: Br₂, anhydrous FeBr₃.
    2. Bromobenzene to toluene: CH₃Br, Na, dry ether.
  • Benzene → Benzaldehyde → Toluene
    1. Benzene to benzaldehyde: CO + HCl, anhydrous AlCl₃ / CuCl.
    2. Benzaldehyde to toluene: Zn-Hg, conc. HCl.
Why these reagents

Reagent and reason, step by step

  • Step 1: Benzene to toluene: CH₃Cl, anhydrous AlCl₃ Friedel-Crafts alkylation; the product is more reactive than benzene, so polyalkylation occurs unless benzene is in excess.
Questions

Benzene to toluene: quick answers

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

1 step: Benzene, then toluene.

Which named reaction is used to convert benzene to toluene?

Friedel-Crafts alkylation. Benzene reacts with an alkyl halide in the presence of anhydrous AlCl3 to give an alkylbenzene.

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

Benzene to toluene: CH₃Cl, anhydrous AlCl₃. Friedel-Crafts alkylation; the product is more reactive than benzene, so polyalkylation occurs unless benzene is in excess.

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