Biomolecules

Long Answer Type

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What happens when D-glucose is treated with following reagents?
(i) Acetic anhydride                  
(ii) Hydroxylamine
(iii) Tollen’s reagents              
(iv) Fehling solution
(v) Phenyl hydrazine.

(i) Acetylation of glucose with acetic anhydride gives glucose petnaacetate which confirms the presence of five -OH groups.



(ii) Glucose reacts with hydroxylamine to give monoxime. This reaction confirms the presence of a carbonyl group.



(iii) Glucose reduce ammonical silver nitrate (Tollen’s reagent) to metallic silver.


(iv) Glucose reduces Fehling’s solution and gives brick red precipitate due to formation of cuprous oxide (Cu2O):


(v) D-glucose reacts with phenylhydrazine to give glucose phenylhydrazone which is soluble in water. If excess of phenylhydrazine is used, dihydrazone, known as glucosazone is formed.
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