- Seliwanoff's test
Seliwanoff’s test is utilized to differentiate between
aldoseand ketose sugars. The reagents consist of resorcinoland conc. HCl, acid hydrolysis of polysaccharides and oligosaccharides thus yielding simpler sugars. A ketose is present if the mixture turns red. Ketoses are distinguished from aldoses via their ketone/ aldehydefunctionality. If the sugar contains a ketone group, it is a ketose and if it contains an aldehyde group, it is an aldose. When heated, ketoses are more rapidly dehydrated than aldoses. The dehydrated ketose then reacts with the resorcinolto produce a deep cherry red color. Aldoses may react slightly to produce a faint pink color.Fructose and sucrose are two common sugars which give a positive test.Sucrose, a disaccharide consisting of fructose and glucose, also gives a positive test. This is due to the presence of concentrated HCl, which hydrolyses sucrose into its monosaccharide subunits. Thus fructose, being a keto sugar, give positive Seliwanoff's test.
[http://188.8.131.52/search?q=cache:cUQwYymZKwAJ:acad.erskine.edu/facultyweb/baker/BG320/handouts/Lab%2520materials/carbohydrates%2520lab.doc+Seliwanoff%E2%80%99s+Test&hl=tl&gl=ph&ct=clnk&cd=6 Qualitative Analysis of Carbohydrates]
#Theodor Seliwanoff, "Berichte der deutschen chemischen Gesellschaft", 1887, 20(1), 181-182
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