Question

A positive Seliwanoff's test is obtained with?

• A. Glucose
• B. Fructose
• C. Galactose
• D. Mannose

Answer 1

The correct option is B

Fructose

The correct option is B.

Explanation of correct option:

1. Seliwanoff’s test is a compound test performed to separate aldose and ketose sugars. When heated, ketones quickly dry out than the aldoses.
2. Materials required: Seliwanoff’s Reagent, sample given to test the presence of keto sugar.
3. Principle: Keto sugars get dried out in the nearness of concentrated acids to yield furfurals or their subsidiaries which react with resorcinol in Seliwanoff reagent to yield a cherry-red hue complex as the positive result.
4. Procedure:
   1. Take a test tube, and add 5 ml of Seliwanoff’s reagent to it.
   2. The amount of reagent shouldn’t exceed 5 ml and measure it carefully.
   3. Add the 1ml sample.
   4. Heat the solution using boiling water.
   5. Boil the solution in boiling water for about 5 minutes
5. Observation: If the color turns Red, it shows a positive result and the presence of keto sugar.

Final answer: A positive Seliwanoff's test is obtained with fructose.