Question

Which of the following tests does glucose give?

(a) Tollen’s test

(b) 2,4-DNP test

(c) Schiff’s test

(d) Addition product with NaHSO3

The question was asked by my college professor while I was bunking the class.

This intriguing question originated from Biomolecules Carbohydrates topic in section Biomolecules of Chemistry – Class 12

Answer 1

Right answer is (a) Tollen’s test

Explanation: Despite having a CHO group, glucose does not react with NaHSO3 to form an addition product and give either Schiff’s test or 2,4-DNP test like other aldehydes. However, it forms a silver mirror on treatment with Tollen’s reagent. These observations indicate the existence of glucose in other forms and gave way to the cyclic structure of glucose.