Submitted by Graham Edgar and W. S. Hinegardner.
Checked by H. T. Clarke and Ross Phillips.
1. Procedure
(
A)
Creatinine.—A mixture of
900 g. (6 moles) of commercial creatine hydrate (Note
1) with
550 cc. of concentrated hydrochloric acid (sp. gr. 1.19) and 150 cc. of water is warmed in a
3-l. flask on the
steam bath for twenty-four hours (Note
2). The hot solution is filtered and chilled to 0–5° in an
ice bath, and to it is added
1 l. of 28 per cent aqueous ammonia (sp. gr. 0.90). The flask is immersed in an
ice-salt bath, and the mixture is stirred vigorously until the temperature falls to 0°, when the crystalline
creatinine is filtered off, washed with ice-cold
28 per cent aqueous ammonia (Note
3) until the filtrate is free of
chlorides, and finally with ice-cold
methyl alcohol; the product (Note
4) is then dried to constant weight at 40–50°. The yield (Note
5) is
545–555 g. (
80–81 per cent of the theoretical amount).
(
B)
Creatinine Zinc Chloride.—An intimate mixture of
400 g. (2.7 moles) of commercial creatine hydrate and
400 g. (2.9 moles) of fused zinc chloride is heated in a
porcelain dish over a small flame. The mixture melts to a viscous liquid which soon solidifies. The flame is removed when the mixture can no longer be stirred. The mass, when cold, is broken up, and stirred with 500 cc. of cold water until the lumps are softened; the crude
creatinine zinc chloride is filtered off with suction on a hardened
filter paper and washed with ice water to remove excess
zinc chloride. The crude material is now dissolved in
6 l. of boiling 25 per cent aqueous acetic acid, filtered with the use of a little
decolorizing carbon, and the solution allowed to stand for forty-eight hours. The crystals that have separated are filtered off, washed with ice water, and dried. The weight is
220–230 g. The filtrate and washings are evaporated to 4.5 l. under reduced pressure in a
12-l. flask;
6.5 l. of methyl alcohol is added and the mixture allowed to stand in a cool place for twenty-four hours. The crystals that separate are filtered off, washed with cold water and dried, and an additional
150–160 g. is thus obtained. The total yield is
370–380 g. (
76–78 per
cent of the theoretical amount).
(
C)
Creatinine Picrate.—A mixture of
300 g. (2 moles) of commercial creatine hydrate with
190 cc. of concentrated hydrochloric acid (sp. gr. 1.19) and 50 cc. of water is warmed in a
glass or
porcelain dish on a steam bath for twenty-four hours. The resulting mass of
creatinine hydrochloride crystals is dissolved in 1 l. of water, boiled with a little
decolorizing carbon, and filtered. The solution is then diluted to 4 l. with distilled water, and heated to boiling in a 12-l. flask under a
reflux condenser. To the hot solution is added, with good stirring, a solution of
500 g. (2 moles) of technical picric acid (containing 10 per cent of water) in
1250 cc. of warm methyl alcohol. Stirring is continued for one hour on the steam bath and the solution allowed to cool. The crystalline precipitate of
creatinine picrate is filtered off, washed well with cold water, and dried. It forms long needles which melt at
220°; the melting point (Note
6) is unchanged on recrystallization from hot water. The yield is
620–630 g. (
89–90 per cent of the theoretical amount).
2. Notes
1. As a rule, the commercial product, which contains one mole of water of crystallization, is entirely satisfactory; but if it is dark in color, it may be recrystallized from water with the use of
decolorizing carbon.
2. It is suggested that the
hydrochloric acid solution of
creatine should be thoroughly decolorized with
Norite before precipitation inasmuch as any color tends to come down with the
creatinine. Some of the commercial
creatine contains traces of
iron, in which case the addition of
3–4 g. of tartaric acid before treating with
ammonia will retain the
iron in solution, keeping it from precipitating with and staining the
creatinine (W. W. Hartman, private communication).
4. The
creatinine so prepared is practically 100 per cent pure; its recrystallization, while not recommended, may be carried out by dissolving, as rapidly as possible, 1 part by weight in 5 parts of water previously warmed to 65°, and then immediately adding to the warm solution double its volume of
acetone, chilling in ice, and filtering after a few hours. The product is finally washed with
acetone and dried. About one-third is lost in the filtrate.
5. The yield could be slightly increased by so modifying the conditions that the total volume of filtrate would be small
er, but this would involve an undue amount of trouble.
6. Special attention was given to the melting-point determination, since two values,
205° and
212–213°, have been recorded in the literature.
3. Discussion
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