CHEMICAL PROPERTIES 



373 



Alloxan ate 



ylalloxan decomposes even more rapidly than alloxan; since enolization 

 cannot occur in this compound it was concluded that enolization with 

 subsequent ionization is not important, and the reaction was written 

 as base-catalyzed. It was always assumed that C-4 joined to C-6 in the 



HN 



V. 



H 



OH 



HN 



,o 



OH 

 O' 



A ^°" 



N^^COO 

 H 



rearrangement, the carboxylate group arising from C-5, but recent work 

 has cast doubt on this (Kwart and Sarasohn, 1961; Kwart et al., 1961). 

 When alloxan-5-C^^ is converted to alloxanate, the labeling is found not 

 in the carboxylate group but the ring, so there is not only a C — C shift 

 but also a C — N shift involved, C-5 joining to N-1. It was also shown that 

 the dianion undergoes a similar rearrangement, so that the dependence on 



Fig. 4-1. Destruction of alloxan at pH 5.5-6.2 and 

 16°: (1) whole blood; (2) plasma; (3) serum; (4) phos- 

 phate buffer. (From Veksler, 1956.) 



