Question
Describe laboratory method for preparation of glucose. Write the reaction that indicates the presence of $CHO$ group in glucose.
✓
Answer
The oxidation of glucose with bromine water $($which is a mild oxidizing agent$)$ forms gluconic acid. This indicates presence of aldehyde group.
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 $H_2SO_4$ in alcoholic solution
By boiling starch with dilute $H_2SO_4,$ at $393 K,$ under pressure
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 $H_2SO_4$ in alcoholic solution
By boiling starch with dilute $H_2SO_4,$ at $393 K,$ under pressure
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