Aldehydes Ketones And Carboxylic Acids

The Etard reaction is a well-known organic reaction used for the selective oxidation of methyl groups attached to aromatic rings into aldehyde groups. Here's how the process works in detail:
Step 1: Reactants Involved
The starting compound is toluene ( ).
The reagent used is chromyl chloride ( ) in a non-aqueous solvent like carbon tetrachloride ( ).
Step 2: Formation of the Etard Complex
Chromyl chloride reacts with the methyl group of toluene to form a complex known as the "Etard complex." This is a coordination complex where the chromium atoms temporarily bind with the benzylic hydrogen atoms.
Step 3: Hydrolysis of the Complex
Upon subsequent hydrolysis with water (usually dilute acid), the complex decomposes and the methyl group is oxidized into a formyl group ( ).
Step 4: Final Product
The final product of this reaction is benzaldehyde ( ).
Summary:
This reaction is named after the French chemist Alexandre Etard and is specifically useful for converting alkylbenzenes to aromatic aldehydes without further oxidation to acids. That is why it is the correct answer here.