Question

\[Sucrose( + )\] on hydrolysis gives a mixture of \[D - ( + )glucose\] \[{[\alpha ]_D}\] = \[{52.7^ \circ }\] and \[D - ( - )fructose = - {92.4^ \circ }\] known as invert sugar. Calculate the rotation of mixture:
A) \[ - {19.9^\circ }\]
B) \[ + {19.9^\circ }\]
C) \[ - {21.4^\circ }\]
D) \[ + {21.4^\circ }\]

Answer 1

Hint: The word hydrolysis comes from the word hydro, which is Greek for water, and lysis, which means "to unbind". Its simplest definition, hydrolysis is a chemical reaction in which water is used to break down the bonds of a particular substance.

Complete step by step answer:
Hydrolysis of sucrose is given by the following reaction.
\[Sucrose + {H_2}O \to (Glucose + Fructose)\]
We know that 1 mole of sucrose yields 1 mole of glucose and 1 mole of fructose. Hence, the specific rotation of mixture will be one half of the sum of the specific rotation of the two monosaccharides glucose and fructose.
\[{[\alpha ]_D}\;\] of invert sugar $ \to $
\[= \dfrac{1}{2}[{52.7^\circ} + ( - {92.4^ \circ})] \\
= \dfrac{1}{2}[{39.7^\circ }] \\
= - {19.9^\circ}\]

Hence, option (A) is correct.

Additional Information: In this question, a word “invert sugar” is used. Inverted or invert sugar is a mixture of glucose and fructose; it is obtained by splitting sucrose into these two components. The mixture is sold as a viscous liquid and is often referred to as trimoline or invert syrup. Compared to sucrose, inverted sugar is sweeter and its products (glucose and fructose) tend to retain moisture and are less prone to crystallization.

Note: Students may be confused in writing the molecular formula of glucose and fructose. It is interesting to note that the molecular formula for both the compounds is the same that is \[{C_6}{H_{12}}{O_6}\]. The molecular formula of sucrose is \[{C_{12}}{H_{22}}{O_{11}}\].