Organic Syntheses, Coll. Vol. 4, p.763 (1963); Vol. 30, p.72 (1950).
Avoid contact with styrene dibromide
, which is a skin irritant. This preparation should be conducted in a hood
to avoid exposure to ammonia
A 5-l. three-necked flask
is equipped with a high-speed, motor-driven stirrer
passing through a bushing in the center neck (Note 1)
. The side necks are equipped with rubber stoppers
each carrying a short length of 8-mm. glass tubing, bent at right angles. A 10–12 in. length of stout, flexible iron wire
is passed through one of these pieces of tubing. Two liters of liquid ammonia (Note 2)
and 2 g. of ferric nitrate hydrate
are placed in the flask. One hundred grams of sodium (4.35 g. atoms)
is cut into rectangular pieces about 3 by
in. in size. One of the pieces of sodium
is hooked onto the lower end of the iron wire
and lowered into the liquid ammonia
. Stirring is not necessary during this part of the reaction, but it is advisable. When the lump of sodium
has reacted, the solution turns from blue to gray, and the remaining pieces of sodium
are added in the same manner. The addition requires about 45 minutes (Note 3)
The stopper carrying the iron wire
is removed, 2 g. of anil is added, and then 528 g. (2 moles) of finely powdered, dry styrene dibromide
is added gradually with vigorous stirring. The addition requires about 1 hour (Note 4)
. Stirring is continued for 2 hours (Note 5)
after the addition has been completed, after which 600 ml. of concentrated ammonium hydroxide
is added, followed by 1 l. of distilled water, and the mixture is allowed to stand until the frost on the outside of the flask is entirely melted.
The aqueous solution is then steam-distilled from the same flask (Note 6)
until no more oil passes over. This usually requires about 6 hours, and 1.5–2 l. of distillate is collected. The phenylacetylene
in the distillate is separated and washed several times with distilled water to remove ammonia (Note 7)
. The washed material is dried over anhydrous magnesium sulfate
and distilled through an efficient column (Note 8)
under reduced pressure. Almost the entire product distils at 73–74°/80 mm.
The yield is 93–106 g.
A suitable stirrer has been described earlier.2
Additional liquid ammonia
should be added from time to time. Liquid ammonia
can be handled satisfactorily in fairly large amounts in an open flask, as the frost that quickly forms on the outside of the flask slows down evaporation.
This is an excellent method for making sodium amide
for many purposes. If the sodium amide
is to be used in another solvent, the solvent should be added to the liquid ammonia
after the sodium amide
is prepared; the ammonia
is allowed to evaporate, and the last traces of ammonia
are expelled by heating the flask on a steam bath
The styrene dibromide
must not be added too rapidly, or the heat of reaction may cause rapid boiling of the ammonia
and possible loss of part of the mixture.
In one run an increase of this stirring period to 2.8 hours resulted in an 11%
increase in yield.
Because the large amount of ammonia
that comes over may entrain considerable phenylacetylene
, a very efficient cooling system3
If acid is used to remove the ammonia
, the product is likely to be dark colored.
The checkers used an 18-in. column packed with Berl saddles
This preparation is referenced from:
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