Checked by Roger Adams and H. A. Stearns.
1. Procedure
In a
3-l. three-necked flask, provided with a
short reflux condenser, a
mechanical stirrer, and a
separatory funnel, is placed a solution of
636 g. (5.3 moles) of mesitylene (Note
1) in
375–440 cc. of carbon tetrachloride. The flask is placed in an
ice-salt bath, and when the temperature of the reaction mixture is below 10° a solution of
900 g. (288 cc., 5.6 moles) of bromine in
565 cc. of carbon tetrachloride is added to the well-stirred solution. The bromination proceeds very readily, and the
hydrogen bromide which is evolved is led off through the condenser and absorbed in water. The addition of the
bromine solution requires about three hours, during which time the temperature is maintained at 10–15°.
After the addition of the
bromine is complete, the reaction mixture is allowed to stand at room temperature for about one hour. It then has a light yellow color. The solution is washed with water and then with two
500-cc. portions of 20 per cent sodium hydroxide solution to remove any dissolved
hydrobromic acid. The solution is dried over
calcium chloride and filtered. The
carbon tetrachloride is distilled through a good
column until the temperature at the top of the column reaches about 120°. When the
carbon tetrachloride has distilled, the oil is likely to turn dark and give off fumes.
The residue is added to a solution of
50 g. of sodium in about a
liter of 95 per cent alcohol. The solution is boiled under a reflux condenser for about one hour (Note
2) and then allowed to stand overnight. The reaction mixture is diluted with about 6 l. of water and the two layers are separated. The aqueous layer is extracted with three or four
500-cc. portions of carbon tetrachloride (Note
3), and the extracts are added to the
bromomesitylene. This solution is then washed thoroughly with water. The
carbon tetrachloride solution is separated, dried over
calcium chloride, and distilled. After the
carbon tetrachloride is removed the
bromomesitylene is fractionated carefully under reduced pressure from a
modified Claisen flask. The fraction boiling at
105–107°/16–17 mm. (Note
4) is
bromomesitylene. The yield is
840–870 g. (
79–82 per cent of the theoretical amount). There is a small low-boiling portion (about 25 g.) and also a small high-boiling residue. The
bromomesitylene obtained in this way gives no precipitate on standing twenty-four hours with alcoholic
silver nitrate solution. It has a melting point of
−1° to +1°.
2. Notes
3. Discussion
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