Submitted by H. E. Ungnade and E. F. Orwoll.
Checked by C. F. H. Allen and Alan Bell.
1. Procedure
In a
2-l. beaker is placed
75 g. (0.4 mole) of 3-bromo-4-aminotoluene (Note
1), and to it is added the hot diluted acid obtained by adding
72 ml. of concentrated sulfuric acid to 200 ml. of water. The clear solution is stirred and cooled to about 15°, after which 180 g. of ice is added; the amine sulfate usually separates. As soon as the temperature has dropped below +5°, a solution of
32.2 g. (0.47 mole) of sodium nitrite in 88 ml. of water is added from a
dropping funnel, the stem of which extends below the surface of the liquid. The temperature of the solution is kept below +5° during the addition, which requires about 15 minutes. The solution is stirred for 5 minutes after the addition of all the
sodium nitrite, and 300 g. of cold water,
3 g. of urea, and 300 g. of cracked ice are then added successively. The solution is kept in an
ice bath until used.
A
1-l. Claisen flask fitted with a dropping funnel and a thermometer dipping into the liquid is attached to a
condenser set for downward distillation. In the flask are placed
150 g. of anhydrous sodium sulfate,
200 g. (108 ml.) of concentrated sulfuric acid, and 100 ml. of water. The flask is heated over a
wire gauze, and while the internal temperature is maintained at 130–135°, the diazonium solution, in 25-ml. portions, is added at the same rate as the distillate is collected (Note
2). When this operation has been completed, 200 ml. of water, in 25-ml. portions, is introduced and the distillation is continued until an additional 200 ml. of distillate has been collected. The complete distillation requires 3–3.5 hours.
The distillate is extracted with two
150-ml. portions of ether, and the combined extracts are washed successively with 100 ml. of water and
150 ml. of 10% sodium bicarbonate solution. The phenol is then extracted from the
ether layer by use of one
200-ml. and two 50-ml. portions of 10% sodium hydroxide solution. The combined alkaline solutions are acidified, with cooling, by the addition of
100 ml. of concentrated hydrochloric acid. The phenol is extracted with one
200-ml. and two 100-ml. portions of ether, and the combined extracts are washed with 100 ml. of water and dried over
50 g. of anhydrous sodium sulfate. The mixture is filtered, and the
ether is removed from the filtrate by distillation on a
water bath. The residue,
65–72 g. of a brown oil (Note
3), is then distilled from a
Claisen flask with modified side arm; b.p.
102–104°/20 mm. The yield is
60–69 g. (
80–92%) (Note
4).
2. Notes
2. If the diazonium solution is added too rapidly, and the temperature of the liquid falls, the addition is interrupted until the temperature again exceeds 130°.
4. The procedure has been used by the submitters for the conversion of
m-bromoaniline into
m-bromophenol, b.p.
234–237°/742 mm.;
105–107°/11 mm. The yield was
66%.
3. Discussion
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