Mutarotation:
The change in the specific rotation when the two anomeric forms are dissolved in water is known as mutarotation. Both the α and β forms of D(+) glucose are interconvertible through open chain structure. When α – form with specific rotation +112° is dissolved in water it slowly changes to β – form through the open chain structure. Similarly, when β – form with a specific rotation of +19° is dissolved in water it slowly changes to α – form in a similar manner. As a result of its specific rotation increase. Thus we conclude that both the forms in aqueous solution undergo a change in specific rotation and the change continues till the equilibrium, mixture acquires a specific rotation of about +52.7°. It has been established that the equilibrium contains about 36% of a-form and 63.5% of β – form with about 0.5% of open chain structure.
