text: The oxidation of a methyl group occurs widely in nature and industry. The oxidation products derived from methyl are hydroxymethyl group , formyl group , and carboxyl group . For example, permanganate often converts a methyl group to a carboxyl () group, e.g. the conversion of toluene to benzoic acid. Ultimately oxidation of methyl groups gives protons and carbon dioxide, as seen in combustion.