Question

Ketoses are distinguished by which of the following test?

• A. Molisch test
• B. Bial's test
• C. Seliwanoff's test
• D. Benedict test

Hint:

Seliwanoff's test distinguishes ketoses from aldoses; ketoses give a rapid cherry-red colour.

Answer 1

The Correct Option is C

Concept:
Carbohydrates are identified by different chemical tests. Different tests help distinguish general carbohydrates, reducing sugars, pentoses, aldoses, and ketoses.

Step 1: Understanding ketoses.
Ketoses are sugars containing a ketone group. Fructose is a common example of a ketose.

Step 2: Principle of Seliwanoff's test.
Seliwanoff's test is used to distinguish ketoses from aldoses. Ketoses react faster than aldoses in this test.

Step 3: Reagent used.
Seliwanoff's reagent contains resorcinol and concentrated hydrochloric acid.

Step 4: Positive test.
Ketoses give a cherry-red colour quickly due to formation of hydroxymethylfurfural and its condensation with resorcinol.

Step 5: Checking other options.
Molisch test is a general test for carbohydrates.
Bial's test is mainly used for pentoses.
Benedict test is used for reducing sugars.
Seliwanoff's test is specifically used to distinguish ketoses.

Step 6: Final answer.
Therefore, ketoses are distinguished by Seliwanoff's test. \[ \boxed{\text{Seliwanoff's test}} \]