Organic Syntheses, Coll. Vol. 3, p.320 (1955); Vol. 20, p.40 (1940).
In a 2-l. round-bottomed flask
fitted with a three-holed stopper
bearing a mechanical stirrer
, a separatory funnel
, and a gas outlet tube leading to a hood (Note 1)
are placed 1 l. of anhydrous ether (Note 2)
and 156 g. (4 moles) of finely ground sodium amide (p. 778) (Note 3)
. The flask is surrounded by a well-packed ice-salt bath
. To the vigorously stirred mixture 232 g. (4 moles) of dry acetone (Note 4)
is added, dropwise, during a period of 3 hours. With the flask cooled to −10° (Note 5)
, a slow current of acetylene (Note 6)
is passed through the reaction mixture for 2 hours to sweep out the ammonia
. The three-holed stopper is then replaced by a two-holed stopper having a stopcock and an inlet tube reaching to the bottom of the flask and connected with a cylinder of acetylene
. The stopper is wired in. The mixture is placed in an ice-salt mixture (Note 5)
, the whole being mounted on a shaking machine and agitated vigorously for 10 hours; the mixture is kept under a pressure of 10 lb. of acetylene
. Every 30 minutes the pressure is released by means of the stopcock, to sweep out ammonia
formed from small amounts of previously unreacted sodium amide
The reaction mixture is poured cautiously into 800 g. of crushed ice and acidified in the cold by the addition of 400 ml. of 10 N sulfuric acid (Note 7)
. The ether
layer is separated and the aqueous layer extracted twice with 100-ml. portions of ether
. The combined ethereal solutions are dried over 100 g. of anhydrous potassium carbonate
, and the filtered solution is fractionated (Note 8)
. The portion boiling at 103–107°
is collected; any low-boiling fraction is dried and redistilled. The total yield is 135–155 g
) of a colorless product that boils at 103–107° (Note 9)
, (Note 10)
, and (Note 11)
In cold weather, it is convenient to carry out the reaction out-of-doors. This minimizes the attention needed to replace the ice. The outlet tube then opens to the air.
A commercial grade of anhydrous ether
was dried over sodium
The sodium amide
, moistened by the heptane
, was rapidly ground and the solvent allowed to evaporate.
It was found convenient to add Dry Ice to the freezing mixture, thus decreasing the frequency of packing. The temperature never rose above −10° and was usually considerably less.
This is prepared by adding 110 ml. of concentrated sulfuric acid
to 290 ml. of water.
The checkers used a modified Widmer column
There is a considerable quantity of high-boiling material; the quantity and boiling-point range are greater when the shaking is insufficient.
The reaction may be interrupted at several points. After the ammonia
has been swept out by acetylene
, it is usually convenient to place the mixture in a refrigerator
overnight and start the shaking the next day. The shaking period need not be continuous; in this event the chilled mixture is placed in the icebox
The general procedure of Campbell, Campbell, and Eby16
gives excellent yields of ethynylcarbinols.
This preparation is referenced from:
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