Question

Write preparation of glucose from sucrose.

Hint:

This hydrolysis reaction is also called the "inversion of cane sugar" because sucrose is dextrorotatory (rotates plane-polarized light to the right), but the resulting mixture of glucose (dextrorotatory) and fructose (levorotatory) is overall levorotatory. The enzyme used for this is called invertase.

Answer 1

Glucose can be prepared in the laboratory by the hydrolysis of sucrose (cane sugar). Procedure: Sucrose is boiled with a dilute solution of a mineral acid, such as hydrochloric acid (HCl) or sulfuric acid (H\(_2\)SO\(_4\)), for about two hours. The acid acts as a catalyst for the hydrolysis reaction.
Reaction: During this process, one molecule of sucrose breaks down to give one molecule of glucose and one molecule of fructose.
\[ \underset{\text{Sucrose}}{\text{C}_{12}\text{H}_{22}\text{O}_{11}} + \text{H}_2\text{O} \xrightarrow{\text{H}^+ \text{or Invertase}} \underset{\text{Glucose}}{\text{C}_6\text{H}_{12}\text{O}_6} + \underset{\text{Fructose}}{\text{C}_6\text{H}_{12}\text{O}_6} \] The resulting solution contains an equimolar mixture of glucose and fructose. Glucose is less soluble in ethanol than fructose, so adding ethanol to the cooled solution causes glucose to crystallize out, while fructose remains dissolved.