Page 12 - Phytochemistry -1 (PG404) / Clinical Pharmacy 2nd level students ( 2019 )

Clinical pharmacy PharmD program Third level Phytochemistry-1 (PG-504)

2-Avoid sudden cooling as it may break the crystal, examine it without

cover.

3-Monosaccharide gives osazone on hot after 15 min. of heating, while

disaccharides crystallize of osazones is not so easy and take > 30 min.

4-Osazone formation needs  hydroxy aldehyde or ketone, so it is

positive with reducing sugar having free OH in alpha position.

5-Glucose and fructose gives the same osazone; this is because osazone
formation involves the reaction with C₁ and C₂ and the asymmetry in both

carbon atoms is destroyed and the remaining configurations of the last 4
groups are identical in both.

6-Sucose does not give the osazone because the aldehydic group of glucose
and ketonic group of fructose are united together and mask each other.

7-Polysacchrides don't give osazone.

Mechanism

During osazone formation, the hydroxyl group adjacent to the carbonyl

group is oxidized to keto group which is then attacked by phenyl hydrazine
to from osazone.

Special tests

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