Organic Syntheses, CV 4, 396
Submitted by Richard G. Gillis and A. B. Lacey
1.
Checked by B. C. McKusick and R. J. Harder.
1. Procedure
In a
3-l. round-bottomed flask fitted with a
mechanical stirrer and a
reflux condenser is placed
2.0 l. of anhydrous ethanol. To this is added
11.5 g. (0.5 g. atom) of sodium cut into small pieces. When the
sodium is completely dissolved,
23.6 g. (21.0 ml., 0.25 mole) of 1,2-ethanedithiol (p. 401) is added, followed by
47.0 g. (21.7 ml., 0.25 mole) of ethylene dibromide. The mixture is stirred and heated under reflux for 4 hours, cooled, and filtered to remove some
sodium bromide mixed with
polyethylene sulfide. The solid is washed with
100 ml. of ethanol, and the combined filtrates are distilled with stirring. When bumping becomes troublesome, as it generally does when 1.3–1.5 l. of distillate has been collected, the hot reaction mixture is filtered to remove
sodium bromide, and the
sodium bromide is washed with
100 ml. of hot ethanol.
The combined filtrates are returned to the reaction vessel, and distillation with stirring is continued until virtually all the
ethanol has been removed. The distillation is stopped when crystals of
p-dithiane appear in the condenser or when dilution of the distillate with water causes a milky appearance or the formation of a small quantity of crystals. One liter of water is added to the residue, and the stirred mixture is distilled, using the apparatus of
f.htmig. 8 (Note
1), until no more
p-dithiane solidifies in the condenser.
Fig. 8. Apparatus for steam distillation of a solid.
2. Notes
1. The apparatus illustrated is convenient for the steam distillation of compounds which solidify in the condenser. By having the water condenser vertical, it can easily be cleared with a
glass rod. No solidification occurs in the side arm, which behaves as a short air condenser. The
adapter shown need not be specially constructed but may be assembled from commercially available components; the dimensions and joint sizes are not critical.
3. Discussion
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