O=O.[CH3:3][C:4]1[CH:10]=[C:9]([OH:11])[CH:8]=[CH:7][C:5]=1[OH:6].S(=O)(=O)(O)O>C(O)(=O)C>[CH3:3][C:4]1[C:5](=[O:6])[CH:7]=[CH:8][C:9](=[O:11])[CH:10]=1Oxygen was passed into a solution of 0.68 g (2 mmol) of iron 5,14-dihydrodibenzo[b,i][5,9,14,18]tetraaza[14]annulene in 150 ml of 85% by weight aqueous acetic acid and, during this, a solution of 12.4 g (100 mmol) of methylhydroquinone and 0.5 g of concentrated sulfuric acid in 75 ml of 85% by weight acetic acid was added dropwise while stirring vigorously at 40° C. After oxygen up-take ceased, the mixture was subjected to a steam distillation. The distillate was extracted with tert-butyl methyl ether. The organic phase was shaken with aqueous sodium bicarbonate solution and then with water, separated from the aqueous phase, dried over magnesium sulfate, filtered and evaporated to dryness to yield 7.5 g (46%) of 2-methylbenzoquinone in the form of a yellow powder. Melting point 66°-68° C.
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