Question

Polarized light passing through a sugar solution is rotated. A polarimeter allows us to measure the size and direction of the rotation. A freshly prepared solution of alpha-D-glucose shows a specific rotation of +112 degrees. Overtime the rotation of the solution decreases and reaches an equilibrium of specific rotation of +52.5 degrees. In contrast, a freshly prepared solution of beta-D-glucose shows a specific rotation of +19 degrees. The rotation of this solution increases overtime to the same value as that shown by the alpha anomer. a. Draw the Haworth perspective structures of alpha-D-glucose and beta-D-glucose. What feature distinguishes the two forms. b. Why does the specific rotation of a freshly prepared solution of alpha-D-glucose decreases with time? c. Calculate the percentage of the two forms of D-glucose at the equilibrium.

Answer 1

a)

Clho 叶 叶

b. Why does the specific rotation of a freshly prepared solution of alpha-D-glucose decreases with time?

Polarized light passing through a sugar solution is rotated.

A polarimeter allows us to measure the size and direction of the rotation.

A glucose solution rotates the plane to the right.

c)

from given data:

x*112 + (1-x)*19 = 52.5

then

19+ 93x = 52.5

x =0.36

so 36%