Question

$D-(+)-$ Glucose $\xrightarrow{5(CH_3CO)_2O}D-(+)-$ Glucose pentaacetate
Which statement(s) is/are true about glucose pentaacetate?

• A. It will react with phenylhydrazine but not with Tollens’ reagent
• B. It will react with Tollens’ reagent but not with phenylhydrazine
• C. It will react with both of the above mentioned reagents
• D. It will react neither with phenylhydrazine nor with Tollens’ reagent

Answer 1

Answer: (D)

During acetylation of (+)-glucose, it is the $C_1 - OH$ of the hemiacetal that is acetylated and not the $C_5-OH$ that forms the ring (cyclic structure). Since equilibrium with the open-chain aldehyde is prevented, the pentaacetate does not respond to the aldehydic reactions.