Question

7. Draw a Fisher structure for glucose and label the chiral carbons. 8. How does an oligosaccharide differ from a polysaccharide? 9. In the test using Fehling's solution-What element is responsible for the color change? What is the element or compound responsible for each coter listing the color of each?

Answer 1

7. glucose is a monosaccharide .it is and aldo hexose meaning it contain 6 carbon and 1 aldehydic group (CHO).there are 4 chiral centre.

.The fischer projection of glucose is

CHO Ho H N. Ho CHOH [chval aenhe are maked by Scanned with CS CamScanner

8.the difference between oligosaccharide and polysaccharides are

oligosaccharide	polysaccharides
are carbohydrate which is made up of few number of monoccharides units(nearly 10 units)	are carbohydrate which is made up of large number of monoccharides units nearly 100-200 units
they are water soluble	they are water insoluble due increase in hydrophobicity

9.

Fehling test indicates the presence of aldehydic group CHO in the compound is responsible for colour change

Fehling solution is prepared by adding alkaline solution of sodium potassium tartarate to CuSO₄ solution till the precipitate of Cu(OH)₂ formed dissolve to give clear blue solution .when any aldose is heated with this reagent the aldehyde group -CHO group of the aldose gets oxidized to COO^- while Cu²⁺ of Fehling solution is reduced to Cu⁺ (red)

RCHO +2Cu²⁺ +5OH^-$\rightarrow$ RCOO^- +Cu₂O(red) +3H₂O