Question

How is glucose prepared from cane sugar (sucrose)?

Answer 1

Cane sugar (sucrose) is boiled with dilute hydrochloric acid or sulphuric acid. Cane sugar is hydrolysed into an equimolar mixture of glucose and fructose.

\[\ce{\underset{\text{cane sugar}}{C12H22O11} + H2O ->[dil. HCl or H2SO4][\Delta] \underset{\text{glucose}}{C6H12O6} + \underset{\text{fructose}}{C6H12O6}}\]

The mixture is cooled, and alcohol is added during cooling. Glucose crystallises out, and fructose remains in solution. Glucose crystals are separated by filtration.

Answer 2

\[\ce{\underset{\text{Sucrose}}{C12H22O11} + H2O ->[H+][\Delta] \underset{\text{glucose}}{C6H12O6} + \underset{\text{fructose}}{C6H12O6}}\]

Warming with diluted sulphuric or hydrochloric acid for approximately two hours hydrolyses sucrose. Through this hydrolysis, sucrose is converted into a combination of glucose and fructose.

Ethanol is added during cooling to separate glucose from fructose. Since glucose is nearly insoluble in alcohol, it crystallises first. To obtain glucose crystals, the solution is filtered.