Question

Write the reactions involved when D-glucose is treated with the following reagents: (a) HCN (b) Br\(_2\) water 

Hint:

Cyanohydrin formation is a typical nucleophilic addition reaction, and oxidation with bromine water converts aldehydes to carboxylic acids.

Answer 1

Reactions of D-Glucose

(a) Reaction of D-glucose with HCN

Treatment of D-glucose with hydrogen cyanide (HCN) results in cyanohydrin formation at the aldehyde group, yielding D-glucose cyanohydrin.

\[ \text{D-glucose} + HCN \rightarrow \text{D-glucose cyanohydrin} \]

(b) Reaction of D-glucose with Br\(_2\) water

Bromine water, a mild oxidizing agent, oxidizes the C-1 aldehyde group of D-glucose to a carboxylic acid, forming gluconic acid.

\[ \text{D-glucose} + Br_2\text{(water)} \rightarrow \text{Gluconic acid} \]

These reactions confirm the aldehydic character of glucose and its susceptibility to addition and oxidation.