Organic conversion

Benzene to benzaldehyde

1 step: Gattermann-Koch reaction

Class 12, Chapter 8 Aldehydes, Ketones and Carboxylic Acids

Alternative routes (4)

Benzene → Toluene → Benzaldehyde
1. Benzene to toluene: CH₃Cl, anhydrous AlCl₃.
2. Toluene to benzaldehyde: (i) CrO₂Cl₂, CS₂ (ii) H₃O⁺.
Benzene → Chlorobenzene → Toluene → Benzaldehyde
1. Benzene to chlorobenzene: Cl₂, anhydrous FeCl₃.
2. Chlorobenzene to toluene: CH₃Cl, Na, dry ether.
3. Toluene to benzaldehyde: (i) CrO₂Cl₂, CS₂ (ii) H₃O⁺.
Benzene → Bromobenzene → Toluene → Benzaldehyde
1. Benzene to bromobenzene: Br₂, anhydrous FeBr₃.
2. Bromobenzene to toluene: CH₃Br, Na, dry ether.
3. Toluene to benzaldehyde: (i) CrO₂Cl₂, CS₂ (ii) H₃O⁺.
Benzene → Toluene → Benzoic acid → Benzyl alcohol → Benzaldehyde
1. Benzene to toluene: CH₃Cl, anhydrous AlCl₃.
2. Toluene to benzoic acid: KMnO₄, KOH, heat; then H₃O⁺.
3. Benzoic acid to benzyl alcohol: (i) LiAlH₄ (ii) H₃O⁺.
4. Benzyl alcohol to benzaldehyde: PCC.

Why these reagents

Reagent and reason, step by step

Step 1: Benzene to benzaldehyde: CO + HCl, anhydrous AlCl₃ / CuCl Gattermann-Koch reaction generates the formyl cation from CO and HCl.

Questions

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

1 step: Benzene, then benzaldehyde.

Which named reaction is used to convert benzene to benzaldehyde?

Gattermann-Koch reaction. Benzene reacts with carbon monoxide and HCl in the presence of anhydrous AlCl3 and CuCl to give benzaldehyde.

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

Benzene to benzaldehyde: CO + HCl, anhydrous AlCl₃ / CuCl. Gattermann-Koch reaction generates the formyl cation from CO and HCl.