An apparatus is assembled as shown in
f.htmig. 5. The
3-l. three-necked round-bottomed flask A is equipped with a mechanical stirrer sealed with a well-lubricated rubber sleeve. In one neck of the flask are fitted a
thermometer and a
glass tube leading through a safety trap B to a water pump. In the other neck a
7-mm. glass tube, extending to the bottom of the flask, is attached to a
500-ml. bottle C in which is placed
255 ml. (5 moles) of bromine (Note
1). This bottle is connected to a
500-ml. wash bottle D containing
250 ml. of sulfuric acid. The
inlet tube of D is connected to a
calcium chloride tube.
A solution of
430 g. (5 moles) of vinyl acetate (Note
2) in
1.5 l. (26 moles) of absolute ethanol is placed in flask
A. The solution is cooled to about −10° by an ice-salt mixture, and stirring is started. Gentle suction is applied at the outlet tube of
B, and the
bromine is introduced into
A by a rapid current of air. The rate of introduction of the
bromine, controlled by adjustment of the clamp
E, should be regulated so that 8–10 hours is required to volatilize all the
bromine. Stirring is stopped, and the reaction mixture is allowed to stand overnight and to come to the temperature of the room. The mixture is poured into 1.7 l. of ice water (Note
3); the lower layer of
bromoacetal and
ethyl acetate is separated (Note
4), washed twice with 300-ml. portions of cold water and once with
300 ml. of cold 10% sodium carbonate solution, and dried over two successive
25-g. portions of anhydrous calcium chloride for 30 minutes. The crude product weighs
990–1010 g.; it is purified by distillation under diminished pressure (water pump) through a
6-in. Widmer column or a
20-cm. Vigreux column. The first fraction consists of
ethyl acetate; this is followed by the pure
bromoacetal which boils at
62–63°/15 mm. (
84–85°/30 mm.) and which amounts to
610–625 g. (
62–64%) (Note
5).