Question

The reaction of glucose with hydrogen cyanide confirms the

• A. Straight chain structure of glucose.
• B. presence of a carbonyl group in glucose.
• C. presence of $COOH$ group in glucose.
• D. presence of a keto group in glucose.

Answer 1

The correct option is B presence of a carbonyl group in glucose.

Glucose reacts with hydrogen cyanide to form glucose cyanohydrin, where the carbonyl double bond gets cleaved to form one $C-OH$ bond one $C-CN$ bond. This indicates the presence of a carbonyl group but does not confirm whether it is an aldehydic or a keto group.

Heating with $HI$ confirms the presence of straight chain and bromine water test confirms presence of an aldehyde group in glucose.
Hence, (b) is correct.