Barfoed's test
Positive result in Barfoed's test | |
Classification | Colorimetric method |
---|---|
Analytes | Monosaccharides |
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.
Its autor is the 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 copper (II) acetate in 1% acetic acid solution.[4] The reagent does not keep well and it is therefore advisable to make it up when it is actually required.[5]
Procedure
1 drops of Barfoed's reagent is added to 2 mL of given sample in a test tube and boiled for 3 minutes and then allowed to cool. If a red precipitate occurs, a monosaccharide is present.
References
- ^ 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. S2CID 95749674.
- ^ Biochemistry Department. "Colorimetric Identification of Unknown Sugars". Biochemistry Laboratory 353. Smith College. Archived from the original on 2006-07-16.
- ^ William H. Welker (1915). "A Disturbing Factor in Barfoed's Test". J. Am. Chem. Soc. 37 (9): 2227–2230. doi:10.1021/ja02174a036.
- ^ "Barfoed Reagent Safety Data Sheet" (PDF). Broward Central Science. Carolina Biological Supply Company. Archived from the original (PDF) on 14 February 2020. Retrieved 10 September 2020.
- ^ Bowen, Graham and Williams (1957). A Students' Handbook of Organic Qualitative Analysis. University of London Press. p. 73.
- v
- t
- e
- Addition reaction
- Elimination reaction
- Polymerization
- Reagents
- Rearrangement reaction
- Redox reaction
- Regioselectivity
- Stereoselectivity
- Stereospecificity
- Substitution reaction
- A value
- Alpha effect
- Annulene
- Anomeric effect
- Antiaromaticity
- Aromatic ring current
- Aromaticity
- Baird's rule
- Baker–Nathan effect
- Baldwin's rules
- Bema Hapothle
- Beta-silicon effect
- Bicycloaromaticity
- Bredt's rule
- Bürgi–Dunitz angle
- Catalytic resonance theory
- Charge remote fragmentation
- Charge-transfer complex
- Clar's rule
- Conformational isomerism
- Conjugated system
- Conrotatory and disrotatory
- Curtin–Hammett principle
- Dynamic binding (chemistry)
- Edwards equation
- Effective molarity
- Electromeric effect
- Electron-rich
- Electron-withdrawing group
- Electronic effect
- Electrophile
- Evelyn effect
- Flippin–Lodge angle
- Free-energy relationship
- Grunwald–Winstein equation
- Hammett acidity function
- Hammett equation
- George S. Hammond
- Hammond's postulate
- Homoaromaticity
- Hückel's rule
- Hyperconjugation
- Inductive effect
- Kinetic isotope effect
- LFER solvent coefficients (data page)
- Marcus theory
- Markovnikov's rule
- Möbius aromaticity
- Möbius–Hückel concept
- More O'Ferrall–Jencks plot
- Negative hyperconjugation
- Neighbouring group participation
- 2-Norbornyl cation
- Nucleophile
- Kennedy J. P. Orton
- Passive binding
- Phosphaethynolate
- Polar effect
- Polyfluorene
- Ring strain
- Σ-aromaticity
- Spherical aromaticity
- Spiroaromaticity
- Steric effects
- Superaromaticity
- Swain–Lupton equation
- Taft equation
- Thorpe–Ingold effect
- Vinylogy
- Walsh diagram
- Woodward–Hoffmann rules
- Woodward's rules
- Y-aromaticity
- Yukawa–Tsuno equation
- Zaitsev's rule
- Σ-bishomoaromaticity