Glucose does not give2,4- DNPtest , Schiff's test or does not give sodium bisulphite adduct. Give reacsons. Or Despire having an aldehyde group, glucose not give 2,4-DNP test ? What does this indicate ?

Glucose does not give2,4- DNPtest , Schiff's test or does not give sod

1.	Glucose does not give2,4- DNPtest , Schiff's test or does not give sodium bisulphite adduct. Give reacsons. Or Despire having an aldehyde group, glucose not give 2,4-DNP test ? What does this indicate ?
Answer» Solution :Although the open chain structure of glucose does contains an aldehyde group , yetit does not give certain characteristic reactions of the `-CHO` group. Fro example, it neither with2,4-dinitrophenylhydrazine to form a 2,4-DNP derivative nor it gives Schiff's test not it REACTS with a concentrated solution of sodium bisulphite to give sodium bisulphate adduct. (The reason being that glucose actually exists in the CYCLIC hemiacetal form with only a small amount `(LT 0.05 %)` of the open chain form. Since the concentration of therefore , formation of 2,4-DNP derivative or `NaHSO_3` adduct or observation of Schiff's test cannot disturb the equilibrium to regenerate more of the open chain form from the cyclic hemiacetal form and hence does not give these TESTS.