Identifying Reducing Sugars Flashcards
If the saccharide is a reducing sugar, it will reduce copper (II) ions to copper (I) oxide
Benedict’s test
Fehling’s test
Reducing monosaccharides are oxidized by the copper ion in solution to form a carboxylic acid and a reddish precipitate of copper (I) oxide within three minutes.
Barfoed’s test
Reducing disaccharides undergo the same reaction, but do so at a slower rate.
Barfoed’s test
Reduction of Ag+ to Ag. Tollen’s reagent is added to an aldehyde, it precipitates silver metal
Tollen’s test
Glucose and fructose reduces bismuth oxynitrate to bismuth under alkaline conditions
Nylander’s test
CuSO4 in an alkaline solution is reduce to Copper (I) oxide by glucose
Trommer’s test
In the presence of a strong alkali and heat, reducing sugards are converted to caramel
Moore Heller’s test
A solution of reducing sugar when heated with phenyl hydrazine, characteristic yellow crystalline compounds called Osazone are formed.
Osazone Test
Lead acetate is added then filtered and a precipitate will be formed upon the addition of conc. NH4OH
Rubner’s test
Pentoses produces a colored complex when heated with benzidine in glacial acetic acid
Tauber’s Benzidine test
Results: Green to Brick red precipitate
Benedict’s test
Result:
Positive (Glucose, lactose, Fructose): Red-Brown precipitate
Fehling’s test
Result:
Reducing monosaccharides : Red precipitate within 3 minutes
Reducing disaccharides: Red precipitate after 10 minutes
Barfoed’s test
Result: Silver mirror
Tollen’s test
Result:
Positive: Black color (+/-): Brown color
Nylander’s test
Result:
Positive: Yellow red precipitate
Trommer’s test
Result:
1% or less sugar: canary yellow
2% sugar: wine yellow 3% sugar: cherry yellow 4% sugar rum color Above 4% sugar: dark brown or dark color
Moore Heller’s test
Result:
Glucosazone: Needle shaped crystals Galactosazone crystals: rhombic plates Maltosazone crystals: sunflower shaped lactosazone: powder puff/ hedge hog shaped/ fluffy ball shaped
Osazone Test
Result: Lactose: Brick red color with red precipitate Negative: No brick red color
Rubner’s test
Pentoses produces a colored complex when heated with benzidine in glacial acetic acid
Tauber’s Benzidine test
Test for pentose
Tauber’s Benzidine test
Reagent: Lead acetate and conc. Ammonium hydroxide. Test for Lactose
Rubner’s test
Seen under the microscope
Osazone Test
Reagent: 10% KOH
Moore Heller’s test
