Enumerate the reactions of `D`-Glucose which cannot be explained by its open-chain structure.

Explanation

Open structure of D-glucose could not explain the following reactions:
(i) Despite having the aldehyde group, glucose does not give Schiffs 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.
(iv) When glucose is heated with methanol in the presence of dry HCl gas, it forms two isomeric monomethyl derivatives known as `alpha`-D-glucoside `(m.p. = 165^(@)C)` and `beta`-D-glucoside `(m.p = 107^(@)C)`. Since only one molecule of methanol is used for the formation of methyl glucoside, these must be hemiacetals. These results show that glucose does not have open chain form structure.