question_answer 18)

Enumerate the reactions of D-glucose which cannot beexplained by its open chain structure. Give reactions which are characteristic of aldehydic group but not shown glycose as in it free —CHO group is not present  

Answer:

Following reactions cannot be explained by the open chainstructure of D-glucose. (i) Although aldehyde group is present in glucose, it does not give2,4-DNP test, Schiff's test and it does not react with . (ii) The pentaacetate of glucose does not react with hydroxyl amine. (iii) Formation of  and  methyl glucosides cannot be explained byits open chain structure. These are only formed when we assumeits ring structure.