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62-63°/15 mm. (84-85°/30 mm.) and which amounts to 610-625 g. (62-64 per cent of the theoretical amount) (Note 5).
1. The bromine is previously washed with 100 cc. of concentrated sulfuric acid.
2. The vinyl acetate (Eastman Kodak Company) is distilled from the added preservative; the first turbid portion containing water is discarded; and the fraction boiling at 69-71°/740 mm. is used.
3. If an emulsion forms at this point, 320 g. of hydrated sodium sulfate is added.
4. Bromoacetal is a fairly strong lachrymator and is best handled under a hood.
5. A yield of 78 per cent of bromoacetal has been obtained by a slight modification of the procedure described above. One-half of the amounts of materials specified above were used, and, after the bromination was complete, the reaction mixture was allowed to stand for sixty-four hours before it was processed. The yield of bromoacetal was 380 g.1
3. Methods of Preparation
The procedure given above is essentially a large-scale adaptation of that of Filachione.2 Bromoacetal has been prepared by the bromination of acetal directly,3 or in the presence of calcium carbonate;4 by action of sodium ethoxide on a,/3-dibromodiethyl ether;6 by bromination of paraldehyde followed by action of ethyl alcohol;6 and by the action of ethyl alcohol on bromoacetal-dehyde.7
1 Private communication, C. F. H. Allen.
2 Filachione, J. Am. Chem. Soc. 61, 1705 (1939).
* Pinner, Ber. 5, 149 (1872).
4 Fischer and Landsteiner, Ber. 25, 2551 (1892).
* Wislicenus, Ann. 192, 112 (1878).
* Freundler and Ledru, Bull. soc. chim. (4) 1, 75 (1907).
7 Rotbart, Ann. chim. (11) 1, 451 (1934).
3-BROMO-4-HYDROXYTOLUENE (/•-Cresol, 2-bromo-)
Submitted by Í. Å. Ungnade and Å. F. Orwoll Checked by Ñ. F. H. Allen and Alan Bell.
In a 2-1. beaker is placed 75 g. (0.4 mole) of 3-bromo-4-amino-toluene (Note 1), and to it is added the hot diluted acid obtained by adding 72 cc. of concentrated sulfuric acid to 200 cc. 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 cc. 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 fifteen minutes. The solution is stirred for five 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 1-1. 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 cc.) of concentrated sulfuric acid, and 100 cc. of water. The flask is heated over a wire gauze, and while the internal temperature is maintained at 130-135°, the diazo-nium solution, in 25-cc. portions, is added at the same rate as the distillate is collected (Note 2). When this operation has
been completed, 200 cc. of water, in 25-cc. portions, is introduced and the distillation is continued until an additional 200 cc. of distillate has been collected. The complete distillation requires three to three and one-half hours.
The distillate is extracted with two 150-cc. portions of ether, and the combined extracts are washed successively with 100 cc. of water arid 150 cc. of 10 per cent sodium bicarbonate solution. The phenol is then extracted from the ether layer by use of one 200-cc. and two 50-cc. portions of 10 per cent sodium hydroxide solution. The combined alkaline solutions are acidified, with cooling, by addition of 100 cc. of concentrated hydrochloric acid. The phenol is extracted with one 200-cc. and two 100-cc. portions of ether, and the combined extracts are washed with 100 cc. 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 (Org. Syn. 22, ll); b-p- 102-104°/20 mm. The yield is 60-69 g. (80-92 per cent of the theoretical amount) (Note 4).
1. The 3-bromo-4-ammotoluene may be purchased, or prepared according to Org. Syn. Coll. Vol. 1, 1941, 111. The material used melted at 12—13°.
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°.