Tamilnadu BoardEnglish MediumSTD 12ChemistryBiomolecules3 Marks
Question
Prove that sucrose is
invert sugar
non – reducing sugar.
✓
Answer
1. Sucrose is an invert sugar: Sucrose $\left(+66.6^{\circ}\right)$ and glucose $\left(+52.5^{\circ}\right)$ are dextro rotatory compounds while fructose is levo rotatory $\left(-92.4^{\circ}\right)$. During hydrolysis of sucrose, the optical rotation of the reaction mixture changes from dextro to levo. Hence sucrose is also called invert sugar.
2. In sucrose, $C_1$ of $\alpha-D$ glucose is joined to $C_2$ of $\alpha-D$ fructose. The glycosidic bond thus formed is called $\alpha-1,2-$ glycosidic bond. Since both the carbonyl carbons (reducing groups) are involved in the glycosidic bonding, sucrose is a non - reducing sugar.
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