Search:   

Transformation of aldoses into ketoses

Condensation with phenylhydrazine

The reaction of hot phenylhydrazine $ \phi-NH-NH_2 $ with aldoses and ketoses yields osazones, f.i.:

We see that glucosazone and fructosazone are identical! The osazones are yellow solids which crystallize well and which serve to identify the oses

Change from aldose to ketoses

Hydrolysis of osazones provides osones, f.i.:

.. whose cold reduction provides the corresponding ketoses:

Whence the passage Aldose → Osazone → Osone → Ketose

Exercise

Which substance results from the previous reactions on D-galactose?

Answer (Review →   this page and →     this one ): D-galactose →    ..........