PURPOSE: To obtain 2,3-di(lower alkoxy)-5-methyl-1,4-benzoquinone in high yield, by adding an aqueous persulfuric acid salt to a suspension of 3,4,5-tri(lower alkoxy) toluene in a solvent, e.g. water, at a specific temp.

CONSTITUTION: An aqueous persulfuric acid salt (peroxodisulfuric acid salt M2S2O8) is added to a suspension of 3,4,5-tri(lower alkoxy)toluene in a solvent to give 2,3-di(lower alkoxy)-5-methyl-1,4-benzoquinone. The solvent is water, a water-miscible neutral organic solvent, e.g. lower aliphatic alcohol, or their mixture. Since sulfuric acid and its salt are formed from persulfuric acid salt, the reaction proceeds substantially under an acidic condition by acidic sulfuric ion. After the addition of persulfuric acid solution, the mixture is preferably subjected to aging for 1 to several hours in order to terminate the reaction within a few hours. The temperature of the addition and aging is 20W100°C.