Benedicts's Test

Benedicts's Reagent:

Benedict's solution is composed of copper sulfate, sodium carbonate, and sodium citrate (pH 10.5)

Reaction:

Alkaline solutions of copper are reduced by sugars having a free aldehyde or ketone group. the citrate will form soluble complex ions with Cu++, preventing the precipitation of CuCO3 in alkaline solutions.

Method:

Add 1 ml of the solution to be tested to 5 ml of Benedict's solution, and shake each tube. Place the tube in a boiling water bath and heat for 3 minutes. Remove the tubes from the heat and allow them to cool.

Physical propertice:

Formation of a green, red, or yellow precipitate is a positive test for reducing sugars.

Positive Test:

Precipitation of copper(I) oxide as a red, yellow, or yellowish-green solid is a positive test.

Complications:

Not general for simple aldehydes and ketones.
Hydrazine derivatives give a positive test.