The Alkaline Permanganate Oxidation of Dimethylbenzoic Acids and Pseudocumene

Potassium permanganate oxidation of alkyl benzoic acids and pseudocumene has been carried out in an aqueous alkaline solution. 2, 4-and 2, 5-Dimethylbenzoic acids gave 2-methylterephthalic acid and 4-methylisophthalic acid, respectively, as an intermediate in the preparation of trimellitic acid. In the oxidation of 3, 4- dimethylbenzoic acid and competitive oxidation of isomeric toluic acids, the relative reactivity of the methyl groups has been established, as follows : para>reta>ortho. By partial oxidation of mesitoic acid, 2, 6-dimethylterephthalic acid was obtained as main product. In the case of pseudocumene, 2, 4-and 3, 4-dimethylbenzoic, 2-metylterephthalic, and 4-methylisophthalic acids were produced as intermediate products. Their formations were explained by the difference in relative reactivities of the methyl groups.