7.What products are formed when sucrose is hydrolysed? 8. Explain why sucrose an

Question

7.What products are formed when sucrose is hydrolysed?

8. Explain why sucrose and hydrolysed sucrose react differently to Fehling's test.

9. Maltose is a disaccharide consisting of two glucose units. Explain why sucrose andmaltose react differently to Fehling's test. Indicate any relevant feature on the maltose structure.

10. Amylose, one component of starch, is a polymeric version of maltose. What product would be formed when starch is completely hydrolysed?

11. Explain why starch and hydrolysed starch behave differently to Fehling's test.

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Explanation / Answer

7. When sucrose is hydrolysed, it forms 1:1 mixture of glucose and fructose

8. In sucrose, the anomeric carbon is not free. It is involved in glucose and fructose bond, so cant form aldehyde. After hydrolysis it becomes free, so it responds to Fehling's test

9. Maltose is also a dissacharide, it consists of two D-glucose units combined by alpha 1-4 linkage similar to sucrose. In sucrose, glucose and fructose are linked by anomeric carbon. Hence they react differently to Fehling's test.

10. Maltose is formed by hydrolysis of starch. Depending on the relative location of the bond under attack as counted from the end of the chain, the products of this digestive process are dextrin, maltotriose, maltose, and glucose, etc

11. Reason why starch and hydrolysed starch behave differently with Fehling's test is same as sucrose and maltose. In starch, all glucose units are linked by anomeric carbons. After hydrolysis they break into small units and hence respond to Fehling's test.

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