Organic conversion

Toluene to benzaldehyde

1 step: Etard reaction

Class 12, Chapter 8 Aldehydes, Ketones and Carboxylic Acids

Alternative routes (4)

Toluene → Benzoic acid → Benzyl alcohol → Benzaldehyde
1. Toluene to benzoic acid: KMnO₄, KOH, heat; then H₃O⁺.
2. Benzoic acid to benzyl alcohol: (i) LiAlH₄ (ii) H₃O⁺.
3. Benzyl alcohol to benzaldehyde: PCC.
Toluene → Benzoic acid → Benzoyl chloride → Benzaldehyde
1. Toluene to benzoic acid: KMnO₄, KOH, heat; then H₃O⁺.
2. Benzoic acid to benzoyl chloride: SOCl₂.
3. Benzoyl chloride to benzaldehyde: H₂, Pd/BaSO₄.
Toluene → Benzyl chloride → Benzyl alcohol → Benzaldehyde
1. Toluene to benzyl chloride: Cl₂, UV light (or heat).
2. Benzyl chloride to benzyl alcohol: aq. NaOH.
3. Benzyl alcohol to benzaldehyde: PCC.
Toluene → Benzoic acid → Sodium benzoate → Benzene → Benzaldehyde
1. Toluene to benzoic acid: KMnO₄, KOH, heat; then H₃O⁺.
2. Benzoic acid to sodium benzoate: NaOH.
3. Sodium benzoate to benzene: NaOH + CaO (soda lime), heat.
4. Benzene to benzaldehyde: CO + HCl, anhydrous AlCl₃ / CuCl.

Why these reagents

Reagent and reason, step by step

Step 1: Toluene to benzaldehyde: (i) CrO₂Cl₂, CS₂ (ii) H₃O⁺ Etard reaction stops at the aldehyde through a chromium complex that hydrolyses.

Questions

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

1 step: Toluene, then benzaldehyde.

Which named reaction is used to convert toluene to benzaldehyde?

Etard reaction. Toluene is oxidised to benzaldehyde by chromyl chloride in CS2, followed by hydrolysis of the chromium complex.

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

Toluene to benzaldehyde: (i) CrO₂Cl₂, CS₂ (ii) H₃O⁺. Etard reaction stops at the aldehyde through a chromium complex that hydrolyses.