Which of the following reactions and facts of D -glucose cannot be explained by its open chain structure? (i) Despite having the aldehyde group, glucose does not give Schiff test and 2,4-DNP test. (ii) Glucose does not react with sodium hydrogen sulphite to form addition product. (iii) The pentaacetate of glucose does not react with hydroxyl amine showing the absence of free- CHO group.

Question

Which of the following reactions and facts of D -glucose cannot be explained by its open chain structure? (i) Despite having the aldehyde group, glucose does not give Schiff test and 2,4-DNP test. (ii) Glucose does not react with sodium hydrogen sulphite to form addition product. (iii) The pentaacetate of glucose does not react with hydroxyl amine showing the absence of free- CHO group., (i), (ii), (iii), All of above

MARKS App · Accepted Answer

The above behaviour could not be explained by the open chain structure. Because one of the –OH groups of glucose add to the –CHO group and form a cyclic hemiacetal structure. It was found that glucose forms a six membered ring in which –OH at C-5 is involved in ring formation. This explains the absence of –CHO group.

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