Trimethyl- (CAS NO.: ), with other names as 2,5-Cyclohexadiene-1,4-dione, 2,3,5-trimethyl-, could be produced through the following synthetic routes.

A. Disodium nitrosodisulfonate. A 1-l., resin kettle equipped with a mechanical stirrer, a thermometer, a gas-inlet tube suspended about 0.5 cm. above the bottom of the vessel, and an ice-cooling bath is charged with 15.0 g. (0.217 mole) of sodium nitrite, 16.8 g. (0.200 mole) of sodium hydrogen carbonate, and 400 g. of ice. dioxide (25.6 g., 0.400 mole) is passed into the cold, initially heterogeneous mixture with stirring over a period of 40 minutes. Near the end of the addition, the light brown color of the reaction mixture fades almost completely. The resulting colorless to pale-yellow solution of disodium hydroxylaminedisulfonate, which has an approximate pH of 4, is stirred for 10 minutes before 59.5 g. (0.480 mole) of sodium carbonate monohydrate is added, giving a solution of pH 11. The gas-inlet tube is removed from the reaction vessel and replaced with a rectangular anode constructed from a 3.5 cm. by 4.7 cm. piece of stainless-steel mesh (about 16 mesh/cm.) with a stainless-steel wire as an electrical lead. The cathode is a cylindrical coil formed from a 1.5-mm. by 40-cm. piece of stainless-steel wire suspended in a 5-cm. by 10-cm. porous porcelain thimble filled with aqueous 10% sodium carbonate. The porcelain thimble containing the cathode is suspended in the reaction vessel so that the liquid levels in the anode and cathode compartments are the same. The cathode-anode resistance of the electrolysis cell should be in the range of 5–10 ohms. While the reaction solution is continuously stirred and maintained at a temperature of 12° with an ice bath, the electrolysis is started by applying a sufficient potential (approximately 10 volts) to the anode and cathode leads, giving a cell current of 2.0 amp. As the electrolysis proceeds, the potential applied to the cell is adjusted to maintain a cell current of 2.0 amp. The formation of the nitrosodisulfonate radical is evidenced by the appearance of a deep purple color. The electrolysis is continued with stirring and cooling until quantitative measurement of the optical density of the reaction solution, indicates the concentration of disodium nitrosodisulfonate to be 0.42–0.47 M (84–94% yield). The typical reaction time is 4 hours; the amount of electricity passed through the cell totals approximately 28,800 coulombs or 8 amp-hours (theoretically, 19,300 coulombs or 5.4 amp-hours). This solution of the nitrosodisulfonate radical is removed from the anode compartment of the electrolysis cell and used directly in the next step.

B. Trimethyl-p-benzoquinone (CAS NO.: ). The aqueous solution containing approximately 0.17 mole of disodium nitrosodisulfonate is placed in a 1-l., round-bottomed flask fitted with a mechanical stirrer, a thermometer, and an ice bath. A solution of 10.0 g. (0.0734 mole) of 2,3,6-trimethylphenol in 100 ml. of heptane is added to the reaction flask, and the resulting mixture is stirred vigorously for 4 hours with continuous cooling, maintaining the reaction temperature below 12°. The yellow heptane layer is separated, and the brown aqueous phase is extracted with two 100-ml. portions of heptane. The combined heptane solutions are quickly washed with three 50-ml. portions of cold (0–5°), 4 M aqueous sodium hydroxide, followed by two 100-ml. portions of saturated aqueous sodium chloride. The organic solution is dried over anhydrous magnesium sulfate and concentrated at 40° with a rotary evaporator, yielding 10.0–10.9 g. (91–99%) of crude trimethyl-p-benzoquinone as a yellow liquid, which crystallizes when cooled below room temperature. Further purification may be accomplished by distillation under reduced pressure, yielding 8.5–8.7 g. (77–79%) of the quinone, b.p. 53° (0.4 mm.), which crystallizes on standing as yellow needles, m.p. 28–29.5°.