Question

What is Seliwanoff’s Test?

Answer 1

Hint :Seliwanoff’s Test is used to distinguish between aldose and ketose. Ketose are those sugars which have a ketone functional group. While aldose are sugars having an aldehyde functional group.

Complete Step By Step Answer:
Seliwanoff’s test is a biochemical test which is used to identify the presence of ketose and aldose. This test is based on the principle that, on heating or on treatment with a concentrated acid, ketoses dehydrate more rapidly than aldoses.
The reagent used in Seliwanoff’s test consists of resorcinol and concentrated hydrochloric acid. Generally, \[6M{\text{ }}HCL\] is used in this test.
Here, ketoses undergo dehydration to yield \[5 - \] hydroxymethyl furfural. Further, the dehydrated ketose also reacts with resorcinol in a series of condensation reactions to give complex having a deep cherry red colour. The complex produced here is called xanthanoid. This formation of cherry red complex in a sample indicates a positive result that confirms the presence of ketoses.
Aldoses may react slightly to produce a faint pink to cherry colour if it is heated for longer duration (more than ten minutes).
The key takeaways of Saliwanoff’s test are product and reaction time of the oxidation reaction helps to distinguish between ketoses and aldoses.
Seliwanoff’s colour reaction is mainly used in the method for the colorimetric determination of fructose in fermentation media.

Note :
Students should note the high concentration of glucose or other sugar can give a false-positive result of Seliwanoff’s test by producing similar coloured compounds. Also, prolonged boiling of glucose can also produce an incorrect result as glucose undergoes a catalytic action of acid and becomes fructose.