A 1000 ml three-necked flask is fitted with a mechanical stirrer, a dropping funnel with stem reaching to almost the bottom of the flask, and another
separatory funnel but with a short stem. The flask is immersed in water maintained at 50°. To the flask, 30 ml of acetone and 150 ml of 20% sodium
carbonate solution are placed. 75 ml of bromine in the long-stemmed funnel and 800 ml of 10% sodium hydroxide solution in the other funnel are placed.
The bromine is slowly added dropwise while stirring into the alkaline mixture. Bromoform starts to separate out and as soon as the bromine is no
longer decolorized, the sodium hydroxide solution is slowly added from the second separatory funnel at such a rate that the mixture in the flask does
not become strongly alkaline. The correct rate of addition of the sodium hydroxide solution is attained when, on stopping the addition, the liquid
immediately assumes the red color of bromine. During the addition, the temperature should be maintained at 45-50° C throughout the experiment. When
all the bromine has been introduced, the addition of the sodium hydroxide is stopped. The heavy layer of bromoform is separated, washed with water,
and dried with anhydrous calcium chloride. The crude bromoform is purified by distillation, preferably in a current of inert gas, and the fraction
boiling at 148-149.5° C is collected yielding 68 grams of pure bromoform (m.p. 7-8° C). Pure bromoform is stabilized with of 4% of its weight of
ethyl alcohol or of a small quantity of diphenylamine.
A text book of practical organic chemistry, by A. I. Vogel, 299, 1974 |