Org. Synth. 1943, 23, 6
Submitted by Dorothy Nightingale
Checked by R. L. Shriner and C. H. Tilford.
In a 500-ml. three-necked flask, provided with a stirrer, are placed 15 g. (0.09 mole) of finely powdered uric acid, 30 g. (25.2 ml.) of concentrated hydrochloric acid, and 40 ml. of water. The mixture is warmed to 30°, the stirrer is started, and 4 g. (0.014 mole) of finely powdered potassium chlorate is added in small portions during a period of not less than 45 minutes (Note 1). Most of the uric acid dissolves; any undissolved material is removed by filtration through a fritted-glass filter. The clear filtrate is diluted with 30 ml. of water, and a rapid stream of hydrogen sulfide is led into it until it is saturated (about 10–15 minutes). Sulfur and alloxantin separate, and the mixture is cooled for 2–3 hours in an ice bath until the separation is complete.
The solid is collected on a Büchner funnel and washed with three 30-ml. portions of cold water. The alloxantin is dissolved by boiling the wet solid for 15 minutes with 250 ml. of water, and the hot solution is filtered to remove the sulfur (Note 2). Alloxantin dihydrate crystallizes from the filtrate in glistening plates which should be pressed as dry as possible on a Büchner filter, washed with about 30 ml. of ether, and dried in a vacuum desiccator (Note 3). The yield is 8–10 g. (55–69%) (Note 4). The product melts with decomposition at 234–238° (Note 5), and is pure enough for most purposes.
It is important that the temperature of the reaction mixture be kept near 30°. The potassium chlorate
must be added slowly.
is difficulty soluble, it is desirable to make a second extraction of the sulfur
to be certain that all the alloxantin
has been removed.
The compound gradually turns pink on standing in the air. It should be stored in a tightly stoppered bottle
or kept in a vacuum desiccator over calcium chloride
If larger amounts of material are desired it is best to oxidize several 15-g. portions of uric acid
and to combine the sulfur-alloxantin mixtures for the extraction.
The water of crystallization may be removed by heating the dihydrate at 120–150° under reduced pressure for 2 hours. The melting points reported in the literature vary considerably. The anhydrous material turns yellow at about 225–230° and decomposes at temperatures ranging from 238–242° to 253–255°, depending on the rate of heating. The instantaneous decomposition temperatures determined on the Maquenne block were 270–275°.
This procedure is essentially that described in the laboratory manual by Fischer and Helferich.1
has been obtained by the oxidation of uric acid
with nitric acid
, followed by reduction with hydrogen sulfide
by oxidation of uric acid
with potassium chlorate
, followed by reduction with stannous chloride
by condensation of alloxan
with dialuric acid
in aqueous solution;4
and by oxidation of dialuric acid
A preparation from alloxan
has been published.6
This preparation is referenced from:
Chemical Abstracts Nomenclature (Collective Index Number);
calcium chloride (10043-52-4)
hydrochloric acid (7647-01-0)
nitric acid (7697-37-2)
hydrogen sulfide (7783-06-4)
potassium chlorate (3811-04-9)
Alloxantin dihydrate (6011-27-4)
dialuric acid (444-15-5)
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