A positive Seliwanoff's test is obtained with? A] Glucose B] Fructose C] Galactose D] Mannose

1 Answer
Apr 4, 2017

Answer:

Fructose

Explanation:

Seliwanoff’s test is a chemical test which distinguishes between aldose and ketose sugars.

A mixture of concentrated HCl and resorcinol of 3ml is added to the sugar.
Then the solution is boiled for little time.
If it is a ketose sugar like fructose and sucrose is the solution turns cherry red .
If it is a aldose sugar then a faint pink color may appear. This experiment is usually experimented with fructose and sucrose but their are many sugars which give a positive test. A positive result can be derived with kiwis or kiwi juice but many kiwis would be required.

The hydrochloric acid reacts with ketose to form
5-hydroxy methyl furfural,C6H6O3 which on condensation forms dehydrated ketose and reaction with resorcinol forms a red colored complex. Fructose is a ketose sugar among all the sugars in the options so it will give a positive test.

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