Question

Why are all monosaccharides reducing sugars but not all disaccharides?

Answer 1

All monosaccharides are reducing sugars because all monosaccharides have an aldehyde group (if they are aldoses) or can tautomerize in solution to form an aldehyde group (if they are ketoses). This includes common monosaccharides like galactose, glucose, glyceraldehyde, fructose, ribose, and xylose. But this does not happen in the case of disaccharides