Question

Sample of Dissacharide does not give red precipitate with fehling solution until it is warmed in dilute HCL, why

Answer 1

Answer:

For a saccharide to react with Fehling’s solution, it must be a reducing sugar. Sucrose is the adduct of fructose and glucose combined in such a way that it is not a reducing sugar. However, HCl will hydrolyze the linkage between glucose and fructose producing a mixture of glucose and fructose, both of which are reducing sugars. Since reducing sugars will react with Fehling’s solution, you see the reaction once hydrolysis has occurred.