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Assertion: A solution of sucrose in water is dextrorotatory. But on hydrolysis in the presence of a little hydrochloric acid, it becomes laevorotatory. 

Reason: Sucrose on hydrolysis gives unequal amounts of glucose and fructose. As a result of this, change in sign of rotation is observed.

(a) Both A and R are true and R is the correct explanation of A

(b) Both A and R are true but R is not correct explanation of A

(c) A is true but R is false

(d) A and R are false

1 Answer

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Best answer

The correct option is: (c)

Explanation:

The hydrolysis of sucrose by boiling with a mineral acid (HCl), produces a mixture of equal molecules of D-glucose and D-fructose. Sucrose solution is dextrorotatory having specific rotation = + 66.5°. But on hydrolysis, it becomes laevorotatory. The specific rotation of D-glucose is + 52° and of D-fructose is -92°. Therefore, the net specific rotation of an equimolar mixture of both is :

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