List of top Chemistry Questions on Carbohydrates asked in CBSE CLASS XII

Assertion (A): Glucose gets oxidized to six carbon gluconic acid on reaction with bromine water. Reason (R): The carbonyl group is absent in the open chain structure of glucose. Choose the correct option:

\(\alpha\)-D-glucose and \(\beta\)-D-glucose differ from each other with respect to the:

What happens when D-glucose is treated with the following reagents? 
(a) Br$_2$ water 
(b) HCN

The suitable Grignard reagent used for the synthesis of

with methanal is:

Carbohydrates are essential for life in both plants and animals. Carbohydrates are used as storage molecules as starch in plants and glycogen in animals. Chemically, they are polyhydroxy aldehydes or ketones. On the basis of their behavior on hydrolysis, carbohydrates are classified as monosaccharides, oligosaccharides, and polysaccharides.
All monosaccharides are reducing sugars, i.e., they are oxidized by Tollens' reagent and Fehling’s solution. A monosaccharide like glucose is an aldose, and its molecular formula was found to be C₆H₁₂O₆. After reacting with different reagents like HI, H₂N–OH, Bromine water, (CH₃)₂O, etc., its structure was found to contain one aldehyde group, one primary alcoholic group (–CH₂OH), and four secondary alcoholic groups (>CHOH).
Despite having the aldehyde group, glucose does not give some of the reactions of aldehyde groups like Schiff’s test or NaHSO₃ addition. This explains the existence of glucose in two cyclic hemiacetal forms, which differ only in the configuration of the hydroxyl group at C–1.