Specific rotation of α and β -D-glucose.
A freshly prepared solution of α-D-glucose shows a specific rotation of +112∘. Over time, the rotation of this solution decreases and reaches an equilibrium value of +52.5∘. In contrast, a freshly prepared solution of β-D-glucose has a specific rotation of +19∘. The rotation of this solution increases over time to the same equilibrium value of +52.5∘.
(a) Why do the specific rotations of the freshly prepared samples change over time, and why do they reach the same equilibrium value?
(b) Calculate the percentage of each anomer at equilibrium.