(a) Use of chromyl chloride (CrO2Cl2): Chromyl chloride oxidises
methyl group to a chromium complex, which on hydrolysis
gives corresponding benzaldehyde Rationalised 2023-24
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Aldehydes, Ketones and Carboxylic Acids
This reaction is called Etard reaction (b) Use of chromic oxide (CrO3): Toluene or substituted toluene
is converted to benzylidene diacetate on treating with chromic
oxide in acetic anhydride The benzylidene diacetate can be
hydrolysed to corresponding benzaldehyde with aqueous acid