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Seliwanoff’s test

Qualitative Test of Carbohydrates Seliwanoff’s test Seliwanoff's test is a chemical test which distinguishes between aldose and ketose sugars. If the sugar contains a ketone group, it is a ketose. If a sugar contains an aldehyde group, it is an aldose. This test relies on the principle that, when heated, ketoses are more rapidly dehydrated than aldoses. Ketoses undergo dehydration in the presence of concentrated acid to yield 5-hydroxymethyl furfural. The dehydrated ketose reacts with two equivalents of resorcinol in a series of condensation reactions to produce a complex (not a precipitate), termed xanthenoid, with deep cherry red color. Aldoses may react slightly to produce a faint pink to cherry red color if the test is prolonged. The product and reaction time of the oxidation reaction helps to distinguish between carbohydrates.