Лако-красочные материалы — производство

In a round-bottomed flask equipped with a stirrer, 100 grams of

2- methylanthraquinone is dissolved in 900 grams of 66° Вё sulfuric acid. The solution is cooled in an ice-salt bath to 0°C. and 50 grams of finely powdered potassium nitrate is added slowly with vigorous stirring. The temperature should be held as near 0° as possible, and must not rise above 5° in any case or appreciable amounts of higher nitration products and oxidation products will be formed. The nitro compound precipitates gradually in the form of microscopic needles. After stirring for 15 hours at 0°, the reaction mixture is poured onto 5 kilograms of ice, and the

7eLocher and Fierz-David, Helv. Chim. Acta, 10, 642 (1927).

precipitated, light yellow product is filtered off and washed with water until all of the acid has been removed.

Purification of the crude product is carried out by boiling it for 6 hours, without previous drying, under reflux with a solution of 100 grams of sodium sulfite in 1 liter water. This treatment does not affect the l-nitro-2-methylanthraquinone, but iso­meric compounds go into solution because, with them, the nitro group is replaced by a sulfo group. The mixture is filtered hot, and the residue is washed with hot water until the wash water, which is dark brown at first, is colorless. After being dried, the product weighs about 98 grams (82 per cent of the theoretical amount), and is in the form of fine, fight gray crystals melting at 265-267 °С. The material is free from isomeric compounds and is sufficiently pure for most purposes. It con­tains traces of unchanged methylanthraquinone which is easily removed by extrac­tion with alcohol. The product, after this treatment, is chemically pure and melts at 269-270°.

(c) l-Amino-2-methylanthraquinone

The moist filter cake of nitromethylanthraquinone, obtained after the purifica­tion with sulfite, is placed in a solution of 200 grams of crystalline sodium sulfide in 2 liters water, and the mixture is boiled under reflux for 2 hours. The mixture is then filtered hot, and the precipitate is washed with hot water until the washings are colorless. The product is pressed out as dry as possible and dried at a moderate temperature (about 80°C.) in order to avoid loss by sublimation. The yield is about 85 grams (97 per cent) of material melting at 198-200°. A chemically pure product, melting at 201-202°, can be obtained by one recrystallization from toluene.