In a
2-l. three-necked flask having ground-glass joints and equipped with a
mechanical stirrer, a condenser (Note
1), and a
dropping funnel are placed
119 g. (0.5 mole) of 1-methylaminoanthraquinone (p. 573) and
600 ml. of pyridine (Note
2) and (Note
3). The stirrer is started, and
90 g. (29 ml., 0.56 mole) of bromine is added over a period of 9–10 minutes. The flask and contents are now heated on the
steam bath for 6 hours with continuous stirring. At the end of this period the hot mixture is transferred from the flask to a
beaker and allowed to cool. The solid that separates (Note
4) is collected on a
Büchner funnel and is washed thoroughly with hot water to remove a considerable portion of
pyridine hydrobromide which is precipitated along with the desired product. The resulting deep red
1-methylamino-4-bromoanthraquinone, after thorough drying, weighs
111–117 g. (
70–74%). It melts at
193–195° and is pure enough for most purposes (Note
5).