Sucrose is dextrorotatory but the mixture

Question:

Sucrose is dextrorotatory but the mixture obtained after hydrolysis is laevorotatory. Explain.

Solution:

Sucrose is dextrorotatory in its aqueous solution and rotates plane-polarized light entering the solution 66.5° to the right. When sucrose is hydrolysed with dilute acids or

invertase enzyme, it gives two products in equimolar concentration, dextrorotatory D-(+)-glucose and laevorotatory D-(-)-fructose. Thus, hydrolysis of sucrose brings

about a change in the sign of rotation, from Dextro (+) to laevo (–). So the hydrolysed mixture is laevorotatory.

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