11.13.5 Osazone Formation

Aldose and ketose react with one equiv of phenylhydrazine to produce phenylhydrazones. In contrast, both C-1 and C-2 react with three equivalent of phenylhydrazine to form a bis-hydrazone known as an osazone (Scheme 7).

Scheme 7

The configuration at C-1 or C-2 is lost in the formation of osazone, C-2 epimers form identical osazones. For example, D-gluose and D-idose are C-2 epimers; both form the same osazone (Scheme 8).

Scheme 8

Ketose reacts with phenylhydrazine at C-1 and C-2 position to form osazone. D-Glucose and D-fructose form the same osazone (Scheme 9).