Question

Fructose and glucose can be distinguished by

• A. Fehling’s test
• B. Barfoed’s test
• C. Benedict’s test
• D. Seliwanoff’s test

Answer 1

The correct option is D Seliwanoff’s test

Both fructose and glucose give following test positive
(i) Fehling’s test (red ppt. of $C{u}_{2}O$ is obtained).
(ii) Barfoed’s test (red ppt. of $C{u}_{2}O$ is obtained)
(iii) Benedict’s test (red ppt. of $C{u}_{2}O$ is obtained)
Seliwanoff’s test is used to differentiate between ketose and aldose. The reagent is a solution of resorcinol in concentrated HCl. The reagent when heated along with a sugar will produce furfural or hydroxy-methylfurfural, which further reacts to give red color. Ketose (fructose) reacts more quickly than aldose (glucose).