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
