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State the limitations of open chain structure of glucose. |
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Answer» Solution :The open chain structure of glucose could not explain the following observations: (i) Despite having the aldehydic group, glucose does not give Schiff.s test and it does not FORM the hydrogensulphite addition product with `NaHSO_(3)`. (ii) The pentaacetate of glucose does not react with hydroxylamine indicating the ABSENCE of free -CHO group. (iii) Glucose is found to exist in two different CRYSTALLINE forms which are named as `alpha`- and `beta` - glucose. The glucose shows the property of Mutarotation i.e., the change in the specific ROTATION. However, the aldehyde does not show the property of the Mutarotation. (iv) On reaction with 1 mole of methanol, it yields two monomethyl derivatives which are known as `alpha`-D-glucoside and `beta`-D-glucoside. |
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