Submitted by K. P. Griffin and W. D. Peterson.
Checked by Nathan L. Drake, Ralph Mozingo, and Jonathan Williams.
1. Procedure
A
5-l. three-necked flask is fitted with a
mechanical stirrer, a
reflux condenser, a
thermometer, and an inlet tube extending to the bottom of the flask (Note
1). In the flask is placed a mixture of
238 g. (1.3 moles) of 2,4-dinitroaniline,
2.4 l. of 95% ethanol, and
1.2 l. of concentrated ammonium hydroxide (sp. gr. 0.90).
The mixture is heated to 45°, and with good stirring
hydrogen sulfide is passed into the reaction mixture while its temperature is maintained between 45° and 55° (Note
2) and (Note
3). The yellow suspended particles of
2,4-dinitroaniline dissolve slowly to form an intensely red-colored solution. The reaction is complete when all the
yellow particles have disappeared; reduction should be complete in 30–60 minutes (Note
4).
The reaction mixture is allowed to stand in an
icebox for 16–18 hours to complete the separation of the product, which forms small, well-defined, deeply red-colored crystals. The
1,2-diamino-4-nitrobenzene is filtered by suction, washed with 150–250 ml. of cold water, and sucked dry on the funnel (Note
5).
The crude product is purified by dissolving it in a boiling mixture of 900 ml. of water and
110 ml. of concentrated hydrochloric acid (sp. gr. 1.19), and filtering the hot solution through a Norit bed using suction. The filter bed is washed with a boiling mixture of 90 ml. of water and
10 ml. of concentrated hydrochloric acid, and the washings are added to the main body of the solution. The filtered solution, while still hot, is treated with
100 ml. of concentrated ammonia (sp. gr. 0.90). The precipitated
1,2-diamino-4-nitrobenzene is filtered hot on a
Büchner funnel, washed on the funnel with 150 ml. of water, and dried in an
oven at 40–50°.
The purified material melts at 197–198° and weighs 105–115 g. (52–58%).
2. Notes
1. The inlet tube should have a diameter of about 15 mm.
2. Enough heat is generated so that it is necessary to play a stream of cold water on the flask from time to time to maintain this temperature.
3. The rate of the gas stream should be as rapid as is consistent with complete absorption.
4. The product may begin to separate during the last few minutes.
3. Discussion
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