Strong oxidizing agents oxidize toluene and its derivatives to benzoic acids. However, it is possible to stop the oxidation at the aldehyde stage with suitable reagents that convert the methyl group to an intermediate that is difficult to oxidize further. The following methods are used for this purpose.

What is the role of H₂SO₄ on oxidation reaction of toluene? 

Dehydrating agent 

H₂SO₄ is a dehydrating agent this is due to the fact that it readily absorbs water from the crystals/ molecules/ compounds.