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Barfoed's test is a chemical test used for detecting the presence of monosaccharides. It is based on the reduction of copper(II) acetate to copper(I) oxide (Cu 2 O), which forms a brick-red precipitate. [1] [2] RCHO + 2Cu 2+ + 2H 2 O → RCOOH + Cu 2 O↓ + 4H + (Disaccharides may also react, but the reaction is much slower.)
Christen Thomsen Barfoed. Christen Thomsen Barfoed (16 June 1815 – 30 April 1889) was a Danish chemist credited with the development of a method to detect monosaccharide sugars in a solution, now known as the Barfoed's test. [1] [2] Barfoed is also credited with having introduced systematic chemical analyses in Danish agricultural sciences. [3]
Benedict's reagent (often called Benedict's qualitative solution or Benedict's solution) is a chemical reagent and complex mixture of sodium carbonate, sodium citrate, and copper(II) sulfate pentahydrate. [1] It is often used in place of Fehling's solution to detect the presence of reducing sugars and other reducing substances. [2]
These specific monosaccharide names have conventional three-letter abbreviations, like "Glu" for glucose and "Thr" for threose. Generally, a monosaccharide with n asymmetrical carbons has 2 n stereoisomers. The number of open chain stereoisomers for an aldose monosaccharide is larger by one than that of a ketose monosaccharide of the same length.
An oligosaccharide has both a reducing and a non-reducing end. The reducing end of an oligosaccharide is the monosaccharide residue with hemiacetal functionality, thereby capable of reducing the Tollens’ reagent, while the non-reducing end is the monosaccharide residue in acetal form, thus incapable of reducing the Tollens’ reagent. [2]
The glycoside bond is represented by the central oxygen atom, which holds the two monosaccharide units together. Monosaccharides can be linked together by glycosidic bonds, which can be cleaved by hydrolysis. Two, three, several or many monosaccharides thus linked form disaccharides, trisaccharides, oligosaccharides, or polysaccharides ...
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Fehling's test can be used as a generic test for monosaccharides and other reducing sugars (e.g., maltose). It will give a positive result for aldose monosaccharides (due to the oxidisable aldehyde group) but also for ketose monosaccharides, as they are converted to aldoses by the base in the reagent, and then give a positive result. [9]