Question

Describe laboratory method for preparation of glucose.

Explain preparation of glucose from sugar cane.

Answer 1

 

Preparation of glucose

Glucose can be prepared in the laboratory by boiling sucrose (cane sugar) with dilute hydrochloric acid or sulphuric acid for about two hours. This hydrolyzes sucrose to glucose and fructose. In order to separate glucose from fructose, alcohol is added during cooling. Glucose is almost insoluble in alcohol. It crystallizes out first, while fructose is more soluble. It remains in the solution. The solution is filtered to obtain the crystals of glucose.

By boiling sucrose with dilute HCl or H₂SO₄ in alcoholic solution

`C_12H_22O_11+H_2O  H^+/""> C_6H_12O_6+C_6H_12O_6`

Sucrose                              Glucose        Fructose

By boiling starch with dilute H₂SO₄, at 393 K, under pressure

`(C_6H_10O_5)_n+nH_2OH^+/"393k,2-3 atoms">nC_6H_12O_6`

 starch or cellulose                                    Glucose