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Chapter 7: Problem 127

Which of the following statements are not correct? (a) Hydrolysis of lactose gives D-glucose and D-galactose. (b) In sucrose, glucose is present in the furanose form while fructose is present in the pyranose form. (c) Gun cotton is cellulose triacetate. (d) On heating with dilute \(\mathrm{H}_{2} \mathrm{SO}_{4}\) under pressure, cellulose undergoes hydrolysis to give D-glucose.

Short Answer

Expert verified
a) Hydrolysis of lactose gives D-glucose and D-galactose. b) In sucrose, glucose is present in the furanose form while fructose is present in the pyranose form. c) Gun cotton is cellulose triacetate. d) On heating with dilute H2SO4 under pressure, cellulose undergoes hydrolysis to give D-glucose. Answer: Statements (b) and (c) are not correct. In sucrose, both glucose and fructose are present in the pyranose form, not the furanose form. Furthermore, gun cotton is a form of nitrocellulose, not cellulose triacetate.

Step by step solution

01

Statement (a)

Hydrolysis of lactose gives D-glucose and D-galactose. This statement is correct. When lactose undergoes hydrolysis, it is broken down into its constituent monosaccharides, D-glucose and D-galactose.
02

Statement (b)

In sucrose, glucose is present in the furanose form while fructose is present in the pyranose form. This statement is not correct. Both glucose and fructose are present in the pyranose form in sucrose. In sucrose, the two monosaccharides are linked by an α(1→2) glycosidic bond, with the glucose in its pyranose form and fructose also in its pyranose form.
03

Statement (c)

Gun cotton is cellulose triacetate. This statement is not correct. Gun cotton is a form of nitrocellulose, not cellulose triacetate. It is produced by treating cellulose with a mixture of nitric acid and sulfuric acid, resulting in the formation of cellulose nitrate. Cellulose triacetate is a different compound used in making photographic films, and it is synthesized using cellulose and acetic anhydride.
04

Statement (d)

On heating with dilute H2SO4 under pressure, cellulose undergoes hydrolysis to give D-glucose. This statement is correct. During the hydrolysis of cellulose, dilute sulfuric acid (H2SO4) acts as a catalyst to break down the β(1→4) glycosidic bonds between the glucose units, converting the cellulose into its monomer, D-glucose. This process can be carried out under pressure and heat to speed up the reaction.

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