What type of sugars can Benedict's reagent detect?

Benedict's reagent is specifically designed to detect reducing sugars, which are sugars that possess free aldehyde or ketone groups that can donate electrons to other molecules. This property allows reducing sugars to react with the cupric ions in the Benedict's reagent, leading to a color change that indicates the presence of these sugars.

Reducing sugars include monosaccharides like glucose and fructose, as well as certain disaccharides such as maltose and lactose. The mention of hemiacetal groups is particularly relevant because reducing sugars often exist in solution as cyclic hemiacetals, which have the reactive aldehyde group.

On the other hand, non-reducing sugars, such as sucrose, do not have free aldehyde or ketone groups, which means they do not react with Benedict's reagent and therefore not detected by it. Starch, a polysaccharide, is also not detected by Benedict's reagent in its typical form because it is primarily composed of amylose and amylopectin, which are large polymers and do not have free reactive groups necessary for the reaction.

Thus, the correct answer emphasizes the reactivity of reducing sugars, making it clear why options referring to non-reducing sugars and polysaccharides like starch do