Studies on the Oxidation of Hexamethylbenzene. I

Oxidation of hexamethylbenzene (1) with diluted nitric acid gave tetramethyl phthalic acid (2), trimethyl trimesic acid (3) and 1, 2, 4-trimethylbenzene-3, 5, 6-tricarboxylic acid (4), the structure of which were determined on the basis of the formation of mellophanic acid, trimesic acid and trimellitic acid, respectively, by decarboxylation followed by potassium permanganate oxidation . The carb oxylic acids (2) and (4) readily dehydrated to the corresponding acid anhydrides. The two tricarboxylic acids (3) and (4) have not been reported yet and their esters also.