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How would you prove the structure of glucose?

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Elucidate the structure of glucose.

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1. Elemental analysis and molecular weight determination show that the molecular formula of glucose is C6H12O6 .

2. On reduction with Conc.HI and red P at 373K, glucose gives a mixture of n – hexane and 2 – iodohexane indicating that the six carbon atoms are bonded linearly.

3. Glucose reacts with hydroxylamine to form oxime and with HCN to form cyanohydrin. These reactions indicate the presence of carbonyl group in glucose.

4. Glucose gets oxidised to gluconic acid with bromine water with bromine water suggests that the carbonyl group is an aldchyde group and it occupies one end of the carbon chain. When glucose is oxidised by conc.HNO3, glucaric acid is formed and it suggest that the other end Id occupied by a primary alcoholi.

5. Glucose is oxidised to gluconic acid with ammoniacal silver nitrate (Toiles reagent) and alkaline copper sulphate (Fehling’s solution). These reactions further confirm the presence of an aldehyde group.

6. Glucose forms penta acetate with acetic anhydride suggesting the presence of five alcohol groups.

7. Glucose is a stable compound and does not undergo dehydration easily. It indicates that not more than one hydroxyl group is bonded to a single carbon atom. Thus the five hydroxyl groups are attached to five different carbon atoms and the sixth carbon is an aldehyde group.

8. The exact special arrangement of – OH groups was given by Emil Fischer as follows.

9. D (+) glucose has D configuration and it is dextro rotatoly.

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