Checked by James Cason and B. H. Walker.
1. Procedure
A.
1-(m-Nitrophenyl)-3,3-dimethyltriazene. To a
3-l. three-necked flask containing
276 g. (2 moles) of technical grade m-nitroaniline (Note
1) are added
250 ml. of concentrated hydrochloric acid and 500 ml. of hot water. The contents of the flask are heated to about 85° to dissolve the
m-nitroaniline; then
550 ml. of concentrated hydrochloric acid is added, and the solution is cooled rapidly. A stirrer, a
thermometer, and a
long-stemmed dropping funnel are attached to the flask, and its contents are then cooled to −3 to −5° by means of a
salt-ice bath. A solution of
144 g. (2.09 moles) of sodium nitrite in 350 ml. of water is added dropwise under the surface of the acid solution while it is being stirred. The rate of addition is regulated (Note
2) so that the temperature does not rise above 0°. The stirring is continued for 15–20 minutes after the
sodium nitrite solution has been added; then a solution of
8–10 g. of urea in 25 ml. of water is added during about 15 minutes (foaming), and the stirring is discontinued. The diazonium salt solution must be kept cold while the next step is proceeding.
Two and one-half liters of water in a
3-gal. crock is stirred vigorously with a mechanical stirrer, and
870 g. (7 moles) of pulverized sodium carbonate monohydrate (Note
3) is added portionwise (Note
4). Crushed ice is added to the
sodium carbonate suspension until the temperature is lowered to 10°; then
423 g. (2.35 moles) of 25% dimethylamine solution (Note
5) is added. The ice-cold
m-nitrobenzenediazonium chloride solution is added over a period of 25–35 minutes under the surface of the vigorously stirred
dimethylamine solution by means of a dropping funnel (Note
6) while the temperature is maintained at about 10° by the addition of ice. The solution is stirred for 15–20 minutes after the addition is complete. The crude yellow triazene is removed by filtration on a
large Büchner funnel. The cake is washed twice by removal and thorough mixing with 2–2.5 l. of water. After the second washing the cake is pressed as dry as possible, then removed and dissolved in
1.8–2.0 l. of boiling 95% ethanol contained in a
4-l. flask under a
reflux condenser. The triazene is allowed to crystallize as the
ethanol is cooled in water, then removed by filtration, and washed with two
200-ml. portions of 95% ethanol. After drying in air at room temperature, the yield of
1-(m-nitrophenyl)-3,3-dimethyltriazene is
348–365 g. (
89–94%), m.p.
100.8–101.5°.
B.
m-Nitrobiphenyl. To a
5-l. three-necked flask equipped with a
sealed mechanical stirrer, a dropping funnel, and a reflux condenser are added
116.4 g. (0.6 mole) of 1-(m-nitrophenyl)-3,3-dimethyltriazene and
2.5 l. of benzene. The
benzene solution is heated to maintain refluxing and stirred vigorously while a solution of
148 g. (0.8 mole) of 94% toluenesulfonic acid (Note 7) in 750 ml. of benzene is added dropwise (Note
8) over a period of 4–4.5 hours. The refluxing is continued for 1–1.5 hours (Note
9) after the
toluenesulfonic acid has been added. The solution is allowed to cool somewhat, 800 ml. of water is added cautiously with stirring through the
separatory funnel, and then the water layer is removed. The
benzene layer is extracted twice with 500-ml. portions of water, then three times with
500-ml. portions of 5% sodium hydroxide solution, and finally with a 500-ml. portion of water. The
benzene solution is shaken with
30–40 g. of anhydrous calcium chloride to remove most of the water. The
benzene is removed by distillation by dripping it into a
500-ml. Claisen flask which is heated sufficiently to maintain a rapid rate of distillation. After most of the
benzene is removed, the residue is transferred to a
125-ml. Claisen flask. The low-boiling material is removed at a pressure of 20–30 mm. up to a bath temperature of 135–140°. The residue is then distilled at 0.1 mm. pressure. After a fore-run of
nitrobenzene (2–5 ml.), the
m-nitrobiphenyl is distilled (Note
10) at
115–118° at 0.1 mm. while the bath temperature is maintained at 155–160°. The yield of the crude yellow oil is
50–60 g. (
42–50%) (Note
11). For purification, the substance is dissolved in
50 ml. of hot methanol. Upon cooling, two layers separate. Crystallization is induced by scratching the inner surface with a
glass rod. When the crystalline mass is cold, the yellow solid is removed by filtration and washed with two
30-ml. portions of cold methanol. After drying in air, the yield of
m-nitrobiphenyl is
40–50 g. (
34–42%), m.p.
58.5–59.5°.
2. Notes
1. E. I. du Pont de Nemours and Company technical product, m.p.
111–112°, was used.
2. The time required for the addition varies from 1.5 to 2 hours.
3. There must be an excess of
sodium carbonate to prevent the troublesome frothing caused by the liberation of
carbon dioxide near the end of the coupling reaction.
5. Obtained from Eastman Organic Chemicals Department, Distillation Products Industries, Rochester, New York.
6. Small portions are added to the separatory funnel while the main portion is kept in the
ice bath.
7.
Monsanto Chemical Company anhydrous toluenesulfonic acid, which is about 80% of the para isomer, was used.
9. The evolution of
nitrogen gas may be followed by attaching a
bubble counter containing kerosene to the top of the reflux condenser. Generally, the evolution of
nitrogen is complete within an hour.
10. The
m-nitrobiphenyl has a tendency to crystallize in the side arm of the Claisen flask. Arrangements must be made to keep the side arm sufficiently warm to prevent crystallization.
11. After the oil has congealed to a solid, the substance melts at
53–57°.
3. Discussion
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