Question

What is mutarotation?

Answer 1

Hint:It was discovered by a French chemist Dubrunfaut in 1844. Cyclic sugars like glucose show mutarotation. It is a consequence of deviation in specific rotation of the two anomeric forms of sugar.

Complete step by step solution:
Let’s look at the answer to the given question:
Mutarotation is defined as the change in the specific rotation of a cyclic sugar because of the change in the equilibrium between isomer and anomer of the sugar in an aqueous solution.
An anomer is a kind of geometric isomerism found in some carbohydrates like glucose. In anomer of the sugar, the C-1 carbon containing the OH group is opposite to the C-5 carbon. While in anomer of the sugar, the OH containing C-1 carbon is on the same side as C-5 carbon.
The specific rotation or optical rotation of an aqueous solution is dependent on the optical rotation of both anomer and anomer of the sugar in an aqueous solution.
Now, let’s try to understand specific rotation.
The specific rotation of an optical compound is defined as the degrees of rotation to which the plane of polarized light is rotated by the optical compound at a particular temperature and concentration. It is the property of an optically active compound.
The rate of mutarotation depends on many factors like temperature, pH of the solution and polarity of the solvent.


Note: All cyclic sugars do not show mutarotation. Sucrose, which is not a reducing sugar, does not show mutarotation. This happens as the glycosidic bond is between the anomeric carbon of fructose and the anomeric carbon of glucose.