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Org. Synth. 1933, 13, 1
DOI: 10.15227/orgsyn.013.0001
ALLANTOIN
Submitted by W. W. Hartman, E. W. Moffett, and J. B. Dickey.
Checked by W. H. Carothers and W. L. McEwen.
1. Procedure
One hundred grams of uric acid (0.595 mole) and 4.5 l. of hot (70–85°) water are placed in a 12-l. round-bottomed flask equipped with a mechanical stirrer. The stirrer is started, and a solution of 80 g. (2 moles) (Note 1) of commercial sodium hydroxide in 120 cc. of water is added. Stirring is continued until the uric acid is in solution (Note 2), after which the solution is cooled by means of a stream of water directed against the flask. When the temperature has fallen to 25–30°, 50 g. (0.32 mole) (Note 3) of potassium permanganate is added all at once (Note 4) to the vigorously stirred solution. Stirring is continued for fifteen to twenty minutes (Note 5), and the mixture is filtered (Note 6) at once through a 19-cm. Büchner funnel. The first fraction of the filtrate contains a small amount of manganese dioxide. This fraction must be collected separately and returned to the funnel. As soon as the filtrate becomes clear it is collected in a 12-l. round-bottomed flask which contains 130 cc. (137 g., 2.2 moles) of glacial acetic acid. The filtrate is tested with litmus to be sure that it is acid, and evaporated to a volume of 1.5–2 l. on a steam bath under reduced pressure (20–30 mm.). The solution thus obtained is allowed to stand in a cool place overnight, and the allantoin which crystallizes is filtered on a 9-cm. Büchner funnel (Note 7). The allantoin is dissolved in 800–900 cc. of boiling water, treated with 5 g. of Norite, and filtered rapidly through a fluted filter paper in a steam funnel. The filtrate is allowed to stand in a cool place overnight (Note 8), and the white crystals of allantoin are separated by filtration with suction. The yield of product melting at 230–231° (Note 9) is 60–71 g. (64–75 per cent of the theoretical amount). If the filtrate from the purification liquors is concentrated to 100 cc., there is obtained an additional 3–5 g. of allantoin.
2. Notes
1. The use of more than 80 g. of sodium hydroxide does not increase the yield, but, if not neutralized immediately upon completion of the reaction, it causes decomposition of some allantoin.
2. It is essential that the uric acid be completely in solution; otherwise not all of it will be oxidized. When the solution is cooled a small amount of white precipitate sometimes separates, but this does not affect the yield.
3. The amount of potassium permanganate can be varied between 50 and 62 g. (0.32–0.39 mole) without changing the yield.
4. The potassium permanganate must be added rapidly (one to five minutes).
5. If the period of stirring is reduced to ten minutes, some unchanged uric acid is recovered. The period can be extended slightly beyond twenty minutes without decreasing the yield of allantoin, but if it is extended beyond one hour the yield is appreciably decreased.
6. Filtration must be as rapid as possible; this necessitates the use of a large Büchner funnel.
7. The filtrate is discarded since the amount of allantoin is not sufficient to repay attempts to separate it from the various other compounds present.
8. Crystallization can be hastened by stirring in an ice bath.
9. The melting point appears to depend somewhat on the rate of heating. The melting point 228–230° is observed in a capillary tube in a bath heated slowly from room temperature. If the capillary is placed in a bath already heated to 228°, the specimen melts at 233–234°. On a copper block still higher melting points are obtained.
3. Discussion
Allantoin has been prepared by the oxidation of uric acid with potassium permanganate,1 lead dioxide,2 potassium ferricyanide,3 oxygen,4 manganese dioxide,5 ozone,6 or hydrogen peroxide,7 and by the electrolytic oxidation of lithium urate.8 It is also formed by heating urea with glyoxylic acid9 or with any one of a number of disubstituted acetic acids such as, for instance, dichloroacetic acid.10

References and Notes
  1. Claus, Ber. 7, 226 (1874); Sundwik, Z. physiol. Chem. 41, 343 (1904); Behrend, Ann. 333, 141 (1904); Biltz, Ber. 43, 1999 (1910); Biltz and Giesler, ibid. 46, 3410 (1913); Biltz and Max, ibid. 54, 2451 (1921); Neubauer, Ann. 99, 206 (1856).
  2. Wöhler and Liebig, ibid. 26, 241 (1838); Mulder, ibid. 159, 349 (1871).
  3. Schlieper, ibid. 67, 214 (1848).
  4. Biltz and Max, Ber. 54, 2451 (1921).
  5. Wheeler, Zeit. für Chem. 1866, 746.
  6. Gorup-Besanez, Ann. 110, 94 (1859).
  7. Venable, J. Am. Chem. Soc. 40, 1099 (1918).
  8. Fichter and Kern, Helv. Chim. Acta 9, 429 (1926).
  9. Grimaux, Ann. chim. phys. (5) 11, 389 (1877).
  10. Merck and Company, Inc., U. S. pat. 2,158,098 [C. A. 33, 6350 (1939)].

Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)

lithium urate

acetic acid (64-19-7)

sodium hydroxide (1310-73-2)

potassium permanganate (7722-64-7)

oxygen (7782-44-7)

Norite (7782-42-5)

urea (57-13-6)

hydrogen peroxide (7722-84-1)

manganese dioxide (1313-13-9)

Allantoin (97-59-6)

uric acid

potassium ferricyanide (13746-66-2)

ozone (10028-15-6)

glyoxylic acid (298-12-4)

dichloroacetic acid (79-43-6)

lead dioxide