Organic Syntheses, CV 4, 702
Submitted by W. T. Smith, Jr. and J. T. Sellas
1.
Checked by N. J. Leonard and R. O. Kerr.
1. Procedure
In a
2-l. three-necked flask equipped with a
mechanical stirrer,
thermometer, and
dropping funnel are placed
500 g. (570 ml., 6.4 moles) of benzene (Note
1) and
34.6 g. (18.8 ml.) of concentrated sulfuric acid (sp. gr. 1.84). The resultant mixture is brought to 20°. To this is added dropwise
201 g. (219 ml., 2.22 moles) of methallyl chloride (Note
2) over a period of 12 hours, during which time vigorous stirring is maintained and the temperature is kept at 20° with the aid of a
water bath. The mixture, which becomes an amber color, is stirred for an additional 12 hours.
The reaction mixture is then transferred to a
1-l. separatory funnel, and the
sulfuric acid layer is removed. The remaining
benzene solution is then washed with four 200-ml. portions of distilled water (Note
3). In this step the amber color disappears and the liquid becomes colorless. The
benzene solution is dried with anhydrous
sodium sulfate and transferred to a
1-l. distilling flask. The
benzene is removed by distillation under a pressure of about 45 mm. The liquid residue is poured into a
500-ml. flask and distilled through a
40-cm. Vigreux column under reduced pressure. The yield of
neophyl chloride boiling at
97–98° /10 mm. is
262–275 g. (
70–73%) (Note
4) and (Note
5);
nD20 1.5250.
2. Notes
2. The
methallyl chloride used was a redistilled commercial sample and had the following properties: b.p.
71–72° /760 mm.,
nD20 1.4274,
d420 0.918.
3. To ensure good results it is necessary to remove all of the
sulfuric acid by washing the mixture thoroughly with water. The final washing should be neutral to litmus.
4. If the residue in the distilling flask is dissolved in
ether, treated with activated
carbon, and evaporated to dryness, the solid so obtained can be recrystallized from about
25 ml. of 95% ethanol to give
10 g. (
2.7%) of
p-di(chloro-tert-butyl)benzene; m.p.
54.5–55.0°.
5. In a run in which the temperature was kept at 10–15° during the addition of
methallyl chloride, the
methallyl chloride was added over a period of 1 hour. Stirring was continued for 1 hour, and the reaction mixture was worked up as described above to give a
53% yield.
3. Discussion
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