The carbohydrates in which the following properties are found are called reducing sugars. The reduction of Tollen’s reagent, Fehling’s solution, Benedict’s solution. All monosaccharides are reducing sugars. Contrary to this the carbohydrates in which the above properties are not found are called non-reducing sugars. For example, sucrose, starch, cellulose, etc. The disaccharides, in which carbonyl group of any one monosaccharide from both the monosaccharides, is present as hemiacetal or ketal and does not involve in glycosidic linkage formation, are reducing. For example, maltose and lactose. Two diastereomeric monosaccharides are called epimers when their configuration differs only at stereogenic centre. Monosaccharides form glycoside with alcohol in the presence of an acid. All monosaccharides show mutarotation.

Which of the following is a non-reducing sugar?

Sucrose

The correct answer is option 2. Sucrose.

Sucrose is a non-reducing sugar. This is because the glycosidic bond between the glucose and fructose molecules in sucrose is formed between the anomeric carbons of the two molecules. The anomeric carbons are the carbon atoms that are involved in the formation of the aldehyde or ketone group in a sugar molecule. When the glycosidic bond is formed between the anomeric carbons, the free aldehyde or ketone group is no longer present, so sucrose is a non-reducing sugar.

Reducing sugars, on the other hand, have a free aldehyde or ketone group. This free aldehyde or ketone group can be oxidized by other molecules, such as Benedict's reagent or Tollen's reagent. When a reducing sugar is oxidized, it changes color. Sucrose does not change color when it is oxidized, so it is a non-reducing sugar.