PRACTICAL ORGANIC AND BIO-CHEMISTRV 



Hydantoin. 



Hydantoin is obtained by heating allantoine and alloxanic acid, two oxida- 

 tion products of uric acid, with hydriodic acid. It is prepared synthetically 

 by heating bromacetyl urea with alcoholic ammonia : 

 JSIH.OC.CH 2 Br ,NH OC 



CO -CO 



\ + HBr 



\NH 2 N NH CH 2 



It is a white crystalline solid which melts at 216. 



Allantoine. 



Allantoine is a combination of 2 molecules of urea with glyoxylic 

 acid, and is derived from the hypothetical dihydroxy-acetic acid : 

 HO CH OH NH CH HN 



COOH CO CO 



NH 2 CO HN 

 Allantoine. 



Allantoine was first found in the allantoic fluid of calves ; it has 

 since been found in the urine of various animals, ox, dog, monkey, 

 rabbit, sheep, and also in various organs of animals. It has been 

 found in plants. Allantoine is an oxidation product of uric acid, and 

 arises in those animals in which allantoine is present in the urine by 

 the oxidation of uric acid. 



Preparation. 



(1) By the Oxidation of Uric Acid. 



100 gm. of uric acid are suspended in 1500-2000 c.c. of water 

 and dissolved by the careful addition of caustic soda in small quantities 

 at a time. The alkaline liquid is treated with a concentrated solution of 62 

 gm. of potassium permanganate and well stirred. Manganese dioxide is 

 formed and the permanganate decolorised. This takes place rapidly and is 

 complete in about an hour ; it must be tested for by filtering a sample if 

 necessary. As soon as the solution is decolorised, it is filtered from manganese 

 dioxide, acidified with acetic acid and evaporated (best in vacud) until it 

 crystallises. The crystals are recrystallised from hot water. 



(2) From the Urine of Dogs, etc. 



The urine is treated with a concentrated solution of phosphotungstic acid 

 to remove pigments, etc. The excess of phosphotungstic acid is removed 

 with lead carbonate and excess of lead with hydrogen sulphide and then the 

 hydrogen sulphide is removed. Chlorides are removed with silver acetate, 

 excess of silver with hydrogen sulphide and the ^hydrogen sulphide by a 

 current of air. The allantoine is precipitated by adding a '5 per cent, 

 solution of mercuric acetate in sodium acetate. The precipitate is filtered 

 off, washed and decomposed with hydrogen sulphide. Allantoine crystallises 

 out on evaporation of the solution. 



