Question

If sucrose is boiled with dilute HCl in alcoholic solution, the ratio in which glucose and fructose are formed is

• A. \(1:1\)
• B. \(1:2\)
• C. \(2:1\)
• D. \(4:1\)

Hint:

Sucrose is a disaccharide made of one glucose unit and one fructose unit. On hydrolysis: \[ \text{Sucrose} \rightarrow \text{Glucose} + \text{Fructose} \] Hence, glucose and fructose are always obtained in an equimolar ratio of \(1:1\).

Answer 1

The Correct Option is A

Sucrose is a disaccharide, one molecule of glucose joined to one molecule of fructose through a glycosidic linkage, so its formula can be thought of as glucose plus fructose minus a water molecule.

Dilute HCl hydrolyses that glycosidic bond by putting a water molecule back in, splitting sucrose exactly at the joint, \(C_{12}H_{22}O_{11} + H_2O \rightarrow C_6H_{12}O_6\ (glucose) + C_6H_{12}O_6\ (fructose)\).

Because the linkage breaks at a single point connecting exactly one glucose unit to exactly one fructose unit, hydrolysing one mole of sucrose can only ever release one mole of each, never more of one than the other.

So glucose and fructose are formed in a 1:1 ratio, and the correct choice is option (1).