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

Explanation

Open chain structure of glucose explains most ofits reactions yet it fails to explain following facts.
i) Glucose reacts with `NH_2OH` to form oxime but glucose penta acetate does not. This implies that the aldehyde group is absent in glucose penta acetate.
ii) D(+) - glucose does not undergo certain characteristics reactions of aldehydes. e.g. glucose does not form `NaHSO_3` addition product, aldehyde- aminonia product & does not respond to schiff.s reagent test.
iii) D(+) - Glucose forms two isomeric methyl glucosides : Aldehyde normally react with two moles of methanol per mole of the aldehyde to form an acetal but D( + }-glucose reacts with only one mole of methanol to form a mixture of two methyl D-glucosides. These glucosides.do not reduce Tollen.s reagent and Fehling solution indieating the absence of - CHO group.