Biomolecules - Result Question 19
####19. Glucose molecule reacts with ’ $X$ ’ number of molecules of phenylhydrazine to yield osazone. The value of ’ $X$ ’ is
(a) four
(b) one
(c) two
(d) three
[1998]
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Solution:
- (d) Glucose reacts with one molecule of phenyl hydrazine to give phenyl hydrazone. When warmed with excess of phenylhydrazine, the secondary alcoholic group adjacent to the aldehyde group is oxidised by another molecule of phenylhydrazine to a ketonic group. With this ketonic group, the third molecule of phenylhydrazine condenses to glucosazone. Therefore, the value of $X$ is 3
Glucose Glucose Phenylhydrozone
$(CHOH)_3$
$CH_2 OH$
Glucosazone
keto compound of glucose phenyl hydrazone
