(
A)
2-Nitrofluorene.—
Sixty grams (0.36 mole) of fluorene (Note
1) is dissolved in
500 cc. of warm glacial acetic acid in a
1-l. three-necked flask fitted with a
thermometer, a
mechanical stirrer, and a
dropping funnel, and supported in a
water bath. The temperature is brought to 50°, and
80 cc. (1.3 moles) of concentrated nitric acid (sp. gr. 1.42) is added with stirring in the course of fifteen minutes. During the addition, the solution becomes slightly yellow, and a small amount of material precipitates. The water bath is slowly brought to 60–65°, when the precipitate dissolves and the color of the solution deepens. Stirring is continued, and heat is applied continuously until the temperature of the mixture reaches 80° (Note
2). After five minutes, the water bath is removed, and the mixture, which now consists of a semi-solid paste of fine, yellow needles, is allowed to cool to room temperature during two hours. The product is collected on a
Büchner funnel, sucked as dry as possible, and washed with two
25-cc. portions of cold glacial acetic acid containing 0.5 g. of potassium acetate. It is then washed several times with water and dried. The
2-nitrofluorene so obtained melts at
155–156° and is sufficiently pure for most purposes. The yield is
60 g. (
79 per cent of the theoretical amount).
If a purer product is desired, the above material may be crystallized from
200 cc. of glacial acetic acid. The purified product melts at
157° and weighs
56 g.
(
B)
2-Aminofluorene.—In a
2-l. round-bottomed flask,
30 g. (0.14 mole) of dried and powdered 2-nitrofluorene is made into a thin paste with
1 l. of 78 per cent alcohol (820 cc. of 95 per cent alcohol and 180 cc. of water). A solution of
10 g. of calcium chloride in 15 cc. of water, together with
300 g. of zinc dust, is added to the suspension, and the whole is thoroughly mixed. The flask is fitted with an
effective reflux condenser, and the mixture is refluxed for two hours.
The sludge of
zinc dust and
zinc oxide is filtered from the boiling solution and extracted (Note
3) with
50 cc. of boiling 78 per cent alcohol. The combined filtrates are then poured into 2 l. of water, whereupon a white, flocculent precipitate is obtained. This is filtered with suction and recrystallized from
400 cc. of hot 50 per cent alcohol. The purified
2-aminofluorene crystallizes in needles melting at
127.5°. The yield is
20–21 g. (
78–82 per cent of the theoretical amount).