Benedict's Test for Reducing Sugars
The Benedict's test allows us to detect the presence
of reducing sugars (sugars with a free aldehyde or ketone group).
All monosaccharides are reducing sugars; they all have a free reactive
carbonyl group. Some disaccharides have exposed carbonyl groups and
are also reducing sugars. Other disaccharides such as sucrose are
non-reducing sugars and will not react with Benedict's solution.
Starches are also non-reducing sugars. The copper sulfate (CuSO4)
present in Benedict's solution reacts with electrons from the aldehyde
or ketone group of the reducing sugar to form cuprous oxide (Cu2O),
a red-brown precipitate.
2 Cu++ + Reducing SugarCu+
The final color of the solution depends on how much
of this precipitate was formed, and therefore the color gives an indication
of how much reducing sugar was present.
Increasing amounts of reducing sugar
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