Organic Syntheses, Coll. Vol. 3, p.260 (1955); Vol. 20, p.37 (1940).
A solution of 134 g. (0.81 mole) of chloral hydrate (Note 1) in 400 ml. of ether (Note 2)
is placed in a 2-l. round-bottomed three-necked flask
equipped with a dropping funnel
, a reflux condenser
, and an efficient mercury-sealed stirrer (Note 3)
. A solution of 12 g. of potassium cyanide (Note 4) in 220 ml. of concentrated ammonium hydroxide
(sp. gr. 0.9) is added through the dropping funnel over the course of 15 minutes at a rate sufficient to cause the ether
to reflux vigorously. Stirring is continued for an additional 20 minutes (Note 5)
. The layers are separated, and the ether
layer is washed once with 75 ml. of water and once with 75 ml. of 10% aqueous sulfuric acid
solution (Note 6)
. (These washings are retained and used again later.) The aqueous layer from the reaction mixture is extracted with three 75-ml. portions of ether
, and each ether
extract is washed successively with the same water and sulfuric acid
solutions used previously. The combined ether
extracts are dried with 40 g. of sodium sulfate
, the ether
is removed by distillation, and the residue is recrystallized from 200 ml. of benzene
. The solid is removed by filtration with suction and washed with two 25-ml. portions of cold benzene
. The yield is 66–76 g.
melting at 97.5–99.5°
(cor.). Concentration of the filtrate gives 1–5 g.
of material with a slightly lower (96–97°
cor.) melting point, making the total yield 67–81 g.
decreases the amount of charring, presumably by controlling the temperature of the reaction mixture.
It is very difficult to prevent the escape of ammonia
. The reaction should be carried out in a hood
A decided increase in reaction time will cause charring and give a product that is difficult to purify. The reaction should not be interrupted until the ethereal extracts have been washed as described.
The ethereal extracts of the reaction mixture contain impurities that cause charring when the solvent is removed. The water and acid treatments remove these impurities. Equally good yields may be obtained by omitting these washings, but then it is necessary to decolorize with Norit in the recrystallization from benzene
, and a second recrystallization may be necessary to obtain a white product.
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