Question

The change in optical rotation (with time) of freshly prepared solution of sugar is known as:

• A. inversion
• B. anomers
• C. mutarotation
• D. epimers

Answer 1

Answer: (C)

(i) Inversion: If the solution obtained after hydrolysis of sugar has opposite sign for optical activity, it is called inversion of sugar.
e. g., $\underset{+66.5^{\circ }}{\mathrm{sucrose}}\to \underset{+52.7^{\circ }}{\mathrm{glucose}}+\underset{92.4^{\circ }}{\mathrm{fructose}}$
(ii) Epimers: These are carbohydrates which differ in configuration at any carbon atom other than glycosidic carbon.
(iii) Anomers: These are carbohydrates which differ in configuration at glycosidic carbon.
(iv) Mutarotation: The change in optical rotation of an optically active compound in solution with time, to an equilibrium value is called mutarotation.
$\underset{+112^{\circ }}{\alpha -D-\text{glucose}}\underset{+52.7^{\circ }}{\text{Eqilibrium mixture}}\underset{+19^{\circ }}{\beta -D-\text{glucose}}$