Organic Syntheses, Coll. Vol. 4, p.329 (1963); Vol. 32, p.55 (1952).
To 400 g. (510 ml., 12.5 moles) of methanol (commercial grade)
in a 2-l. round-bottomed flask
is added in small portions with cooling 200 g. (111 ml., 2.04 moles) of concentrated sulfuric acid
. To this cooled solution is added 100 g. (0.66 mole) of the potassium acid salt of acetylenedicarboxylic acid (Note 1)
. The flask is fitted with a stopper holding a calcium chloride drying tube
and allowed to stand with occasional swirling for 4 days at room temperature.
The liquid in the flask is then decanted from the inorganic salt, which is washed with 500 ml. of cold water. The solutions are combined and extracted with five 500-ml. portions of ether
. The ether
extracts are combined and washed successively with 200 ml. of cold water, 150 ml. of saturated sodium bicarbonate
solution (Note 2)
, and 200 ml. of cold water and then dried over anhydrous calcium chloride
. After removal of the ether
by distillation from a steam bath
, the ester is distilled under reduced pressure from a modified Claisen flask
. The yield of ester boiling at 95–98°/19 mm.
is 67–82 g.
) (Note 3)
and (Note 4)
The potassium acid salt of acetylenedicarboxylic acid is commercially obtainable from the National Aniline Division, Allied Chemical and Dye Corporation, New York, New York
. Directions for the preparation of the free acid are given in earlier volumes.2,3
If the ether
extract is not washed with sodium bicarbonate
solution, considerable loss occurs during the distillation of the ester because of decomposition in the flask.
is a powerful lachrymator and vesicant; it should be handled with extreme care. Even traces of ester on the skin should be washed off at once with 95% ethanol
followed by washing with soap and water.
The same general method has been used by the submitters to prepare diethyl acetylenedicarboxylate
. In this case absolute ethanol
was used, and the ether
extract was dried over anhydrous magnesium sulfate
. The yield of diethyl ester from 100 g. of the acid potassium salt of acetylenedicarboxylic acid
was 57–59 g.
); b.p. 96–98°/8 mm.
This preparation is referenced from:
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