JEE Main levelSingle correct optionDifficulty 2 of 3bm013
Glucose reduces Tollens reagent but does not give the Schiff test or form an addition product with NaHSO3. The best explanation is that
Aglucose has no aldehyde group in any form
Bglucose has a ketone group in the ring
Cthe free aldehyde form is present in only a very small amount because glucose exists mainly as cyclic hemiacetals
Dthe hydroxyl groups permanently block the carbonyl group
Answer: C
Glucose exists mainly as cyclic hemiacetals in equilibrium with a trace of open-chain aldehyde. The aldehyde concentration is too low for the Schiff and bisulphite tests, but it is regenerated as it is consumed in the Tollens reaction.