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

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

Delhi UMET/DPMTDelhi UMET/DPMT 2002

Solution:

(i) Inversion: If the solution obtained after hydrolysis of sugar has opposite sign for optical activity, it is called inversion of sugar.
e. g., $\underset{+66.5^{\circ}}{\text { sucrose }} \rightarrow \underset{+52.7^{\circ}}{\text { glucose }}+\underset{92.4^{\circ}}{\text { fructose }}$
(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.
$\underset{+112^{\circ}}{\alpha - D - \text{glucose}} \underset{+52.7^{\circ}}{\text{Eqilibrium mixture}} \underset{+19^{\circ}}{\beta -D -\text{glucose}}$