Question

Explain:
(i) Muturotation
(ii) Why sucrose is known as invent sugar? How do you account for the fact that sucrose does not reduce Fehling solution? Write Haworth projection formula for sucrose.​

Answer 1

Answer:

You may use sugar on a daily basis by adding it to your recipes and hot beverages to make them sweeter, but there's much more to this white substance than its sweet flavor. Plus, not all sugars have the same chemical properties. While all sugars are soluble, not all sugars are reducing. To understand why sucrose (that's the stuff you add to your favorite hot beverage) is a non-reducing sugar, you have to know the difference between reducing sugar and non-reducing sugar.

Answer 2

(i) Muturotation: In 1846, long before Fischer's Discovery of α- and β- methyl glycosides, it was discovered by Dubrunfat that the rotation of a freshly prepared aqueous solution of D-glucose decreased rather rapidly. After sometime, the value became constant. This phenomenon, called Muturotation, is shown by all aldoses and ketoses. A freshly prepared aqueous solution of D-glucose has a specific rotation of +113°, which gradually falls on standing to a value of +52°. it was later observed (Tarnet 1858) that the rotation of α-D-glucose falling and that of β-D-glucose rising to the same constant value of +52°. it means the value of +52° corresponds to the state of equilibrium between the two forms.

α-D-glucose ⇌ β-D-Glucose

‎ ‎ ‎ ‎+113° ‎ ‎ ‎‎ ‎ ‎ ‎ ‎ ‎ ‎+52° ‎ ‎ ‎ ‎ ‎ ‎+19°

(ii) (i) Sucrose on hydrolysis with dilute acids or with the enzyme invertase produces a mixture of D–(+)–glucose and D–(–)– fructose in equal amounts. since the laevo rotation by fructose (92.4°) is more than dextororotation by glucose (52.5°) so, the hydrolysis mixture is overall laevo rotatory with a specific rotation of -19.85°.

C₁₂H₂₂O₁₁ + H₂O $\large\sf{ \overset{H^{+}}{\longrightarrow}}$ C₆H₁₂O₆ + C₆H₁₂O₆

since this process is accompanied by a change of rotation from dextro to laevo, it is called inversion and the hydrolysis mixture of sucrose is known as invert sugar.

(ii) Sucrose does not reduce Fehling solution since it contains no free aldehyde or ketonic group.

FOR HAWORTH PROJECTION FORMULA OF SUCROSE REFER TO ATTACHMENT.