A solution of
15 g. of sodium dihydrogen phosphate (Note
1) in 5 l. of distilled water is placed in a
6-l. separatory funnel. To this solution is added
90 g. (0.33 mole) of dipotassium nitrosodisulfonate (Fremy's salt) (Note
2). The mixture is shaken to dissolve the inorganic radical. A solution of
16 g. (0.13 mole) of 3,4-dimethylphenol (Note
3) in
350 ml. of diethyl ether is added quickly to the purple solution. As the mixture is shaken vigorously for 20 minutes (Note
4), the color of the solution changes to red-brown. The
o-quinone thus formed is extracted in three portions with
1.2 l. of chloroform. The combined organic layers are dried over anhydrous
sodium sulfate (Note
5), filtered, and evaporated under reduced pressure at 20–23° (Note
6). The residual, somewhat oily, red-brown crystals are slurried twice with
15 ml.-portions of ice-cold ether and collected on a filter. The dark-red crystals, after air drying, weigh
8.7–8.9 g. (
49–50%), m.p.
105–107° (Note
7).