The following reactions cannot be explained by its open chain structure:
(i) Despite having an aldehydic group, glucose does not give Schiff’s test and it does not react with sodium bisulphite and ammonia.
(ii) The penta-acetate of glucose does not react with hydroxylamine indicating absence of —CHO group.
(iii) Mutarotation: When glucose is crystallized from a concentrated solution at 30°C, it gives a form of glucose m.p. 146°C, [α]D = (+) 111°, on the other hand the β-form (m.p. 15°C), [α]D = (+) 19.2° is obtained on crystallization of glucose from a hot saturated aqueous solution at a temperature above 98°C. This behaviour cannot be explained by its open chain structure.
Consider a double helix. Are the base pairs?
part of the backbone structure
inside the helix
outside the helix
