The flask is surrounded by an ice-calcium chloride cooling mixture, and the
aluminum chloride is added in small portions from the Erlenmeyer flask at such a rate that the temperature is maintained between −5° and 0°. After the addition is complete, the mixture is stirred for an additional 30 minutes, and the temperature is then allowed to rise slowly to 10°. The red complex which forms is collected with suction on a
sintered-glass funnel and washed thoroughly with dry
benzene (Note
2). The complex is added in small portions by means of a spatula with stirring to a
600-ml. beaker nearly filled with a mixture of ice and
concentrated hydrochloric acid. The mixture is then allowed to come to room temperature, and the crude ketone is collected on a suction filter.
The product is digested under reflux for about 20 minutes with
100–150 ml. of boiling 95% ethanol. The suspension (Note
3) is cooled quickly almost to room temperature and filtered rapidly with suction to remove any
anthracene. The
9-acetylanthracene, which separates in the filtrate, is redissolved by heating and allowed to crystallize by slowly cooling the solution (finally to 0–5° in an icebox) (Note
4). A second recrystallization from
95% ethanol yields
35–37 g. (
57–60%) of light-tan granules of
9-acetylanthracene melting at
75–76° (Note
5).