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Barfoed's test

Lianyungang Klinechem Co.,Ltd | Updated: Nov 29, 2018

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 (Cu2O), which forms a brick-red precipitate.[1][2]

RCHO + 2Cu2+ + 2H2O → RCOOH + Cu2O↓ + 4H+

(Disaccharides may also react, but the reaction is much slower.) The aldehyde group of the monosaccharide which normally forms a cyclic hemiacetal is oxidized to the carboxylate. A number of other substances, including sodium chloride,[3] may interfere.

It was invented by Danish chemist Christen Thomsen Barfoed[1] and is primarily used in botany.[citation needed]

The test is similar to the reaction of Fehling's solution to aldehydes.

Composition

Barfoed's reagent consists of a 0.33 molar solution of neutral copper acetate[clarification needed] in 1% acetic acid solution. The reagent does not keep well and it is therefore advisable to make it up when it is actually required.[4] May store indefinitely according to several MSDS's.[5][6]

Experiment:- 2-3 dropes of barfoed reagent is added to 1ml of given sample in a testtube and boiled for 30 ses and then allow to cool.

Observation:- Red presipitad is present.

Conclution:- Monosaccharaide is present.

Result:- hence profe the given sample is positive for the presence of monosaccharide.

 

References

1.     Jump up to:a b C. Barfoed (1873). "Über die Nachweisung des Traubenzuckers neben Dextrin und verwandten Körpern". Fresenius' Zeitschrift für Analytische Chemie. 12 (1): 27. doi:10.1007/BF01462957.

2.     Jump up^ Biochemistry Department. "Colorimetric Identification of Unknown Sugars". Biochemistry Laboratory 353. Smith College. Archived from the original on 2006-07-16.

3.     Jump up^ William H. Welker (1915). "A Disturbing Factor in Barfoed's Test". J. Am. Chem. Soc. 37 (9): 2227–2230. doi:10.1021/ja02174a036.

4.     Jump up^ Bowen, Graham and Williams, A Students' Handbook of Organic Qualitative Analysis, University of London Press, 1957, page 73

5.     Jump up^ http://emc-msds.com/chemdocs/34/34634.pdf

6.     Jump up^ http://sargentwelch.com/pdf/msds/Barfoed_Reagent_77.00.pdf[permanent dead link]


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