A
5-l. three-necked round-bottomed flask (Note
1) equipped with a
mercury-sealed stirrer, a
reflux condenser, and a
dropping funnel is set up on a
steam bath. In the flask are placed
50 g. (0.24 mole) of 2-acetylfluorene (p. 23) (Note
2) and
650 ml. of glacial acetic acid. After the ketone has been brought into solution by heating and stirring,
450 g. (1.5 moles) of sodium dichromate dihydrate, previously ground to a coarse powder, is added carefully in small portions (about 10 g. each) (Note
3). Heating and stirring are continued throughout the addition, which requires about 45 minutes. The reaction flask is then removed from the
steam bath, and the solution is brought to gentle reflux over a flame. During a period of 1.5 hours,
200 ml. of acetic anhydride is added through the
dropping funnel. The mixture is refluxed and stirred during this addition and for 8 hours longer (Note
4).
The hot mixture is stirred into 9 l. of hot water in a
5-gal. crock. The suspension is agitated for 15 minutes and is then filtered on a
24-cm. Büchner funnel. The filter cake is washed with four
400-ml. portions of 2% sulfuric acid. The wet filter cake is transferred to a
2-l. beaker containing
700 ml. of a 5% solution of potassium hydroxide (Note
5). The mixture is stirred and heated to about 80°, and the hot solution is filtered. The alkali-insoluble material (Note
6) is washed with
50 ml. of hot 5% potassium hydroxide solution, and the combined alkaline filtrates are placed in a
beaker, stirred with
5 g. of decolorizing carbon for 20 minutes, and again filtered. The solution of the potassium salt is heated with vigorous mechanical stirring to 70°, and
200 ml. of 18% hydrochloric acid is added dropwise, the heating being continued so that the temperature rises to about 85°. The
fluorenone-2-carboxylic acid separates as a thick yellow mass. It is allowed to digest for 10 minutes with stirring, and the hot mixture is filtered on a
24-cm. Büchner funnel. The acid is washed free of
potassium chloride by five or six 200-ml. portions of hot water. The product is pressed as dry as possible and then dried for 3 hours in an
oven at 150°. It is a bright canary-yellow, weighs
36–40 g. (
67–74%), and melts on an
aluminum block at
339–341° (uncor.) with partial sublimation (Note
7).