Question

Hydrolysis of d-sucrose result in change of optical rotation because

• A. number of moles of d-Glucose are less than number of moles of l-Fructose produced during hydrolysis.
• B. Angle of rotation of l-Fructose is greater than AOR of d-Glucose
• C. Both glucose and fructose are levorotatory.
• D. Glucose is l and fructose is d and number of moles of glucose formed during reaction are greater than number of moles of fructose.

Answer 1

The correct option is B Angle of rotation of l-Fructose is greater than AOR of d-Glucose

As hydrolysis of sucrose brings about a change in the sign of rotation, from dextro (+) to laevo (-) which results in change of optical rotation. Sucrose is dextrorotatory, its specific rotation being +66.5%, D-glucose is also dextrorotatory, $[\alpha {]}_D=+53$, but D-fructose has a large negative rotation, $[\alpha {]}_D=92$. Since D-fructose has a greater specific rotation than D-Glucose, the resulting mixture is laevorotatory. Because of this the hydrolysis of sucrose is known as the inversion of sucrose.