Question

What is the structural feature of glucose that makes it a reducing sugar?

Hint:

Reducing sugars contain either an aldehyde or a free ketone group in their open-chain form, which allows them to act as reducing agents.

Answer 1

Glucose is a reducing sugar because it contains an aldehyde group in its open-chain form. The presence of the aldehyde group allows glucose to donate electrons and reduce other compounds, which is the defining characteristic of reducing sugars. In its cyclic form, glucose forms a hemiacetal, but when in an open-chain form, it exposes the aldehyde group. Reducing sugars can reduce compounds such as Benedict’s solution or Fehling's solution, which is a common test for the presence of reducing sugars.