Etard reaction
Toluene is oxidised to benzaldehyde by chromyl chloride in CS2, followed by hydrolysis of the chromium complex.
TolueneC₆H₅CH₃Arene - Step 1
(i) CrO₂Cl₂, CS₂ (ii) H₃O⁺
BenzaldehydeC₆H₅CHOAldehyde
How it works
- Chromyl chloride forms a brown chromium complex with the methyl group.
- The complex does not oxidise further.
- Hydrolysis with H₃O⁺ releases benzaldehyde.
What it makes
Benzaldehyde from toluene.
Where it fails
Use chromyl chloride, not KMnO4, otherwise the acid forms.
Class 12, Chapter 8 Aldehydes, Ketones and Carboxylic Acids
Etard reaction: quick answers
Why does Etard oxidation stop at the aldehyde?
The chromium complex protects the aldehyde until it is hydrolysed.
What does KMnO4 give from toluene?
Benzoic acid.
What is the solvent?
Carbon disulphide.