Question

A non reducing disaccharide 'A' hydrolysis with dilute acid gives an equimolar mixture of D – (+) – glucose and D – (–) – Fructose.
$$\begin{gathered} \mathrm{A}+{\mathrm{H}}_2\mathrm{O}\stackrel{\mathrm{HCl}}{\to }{\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6+{\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6 \\ {\left[\mathrm{\alpha }\right]}_{\mathrm{D}}=+66.5°+52.5°-92.4° \end{gathered}$$

Identify A. What is the mixture of D – (+) glucose and D – (–) – Fructose known as?
Name the linkage that holds the two units in the disaccharide.

Answer 1

Dear Student,
Q20 (a) A is sucrose or cane sugar because sucrose is made up of glucose and fructose monosaccharide components.
Equimolar mixture of D-(+)- glucose and D-(-) fructose is known as invert sugar because sucrose is dextro rotatory having [$\alpha$]_d=+66.5 But the products formed are dextrorotatory (D-(+)glucose ) as well as leavorotatory (D-(-) fructose) since fructose has a higher specific rotation the solution becomes leavoratatory ,This inversion in optical nature leads to the name of invert sugar.
The linkage holding the monosaccharides together is the Glycosidic linkage
Regards!