MOLISCH’S REACTION general reaction for the detection of carbohydrates.
PRINCIPLE:
Sugars on reaction with dehydrating agents like strongly concentrated acids (Concentrated H2SO4) yield furfural and furfural derivatives such as hydroxymethyl furfural, which condense With α-naphthol and give a reddish Violet ring.
REAGENTS:
1.Molisch’s Reagent:
i- α-naphthol,
ii- Ethyl alcohol
2. Concentrated H2SO4
3. Original solution (O.S)- containing a carbohydrate.
PROCEDURE:
- To 2ml of sugar solution (original solution) add 2 to 3 drops of Molisch’s reagent.
- Mix thoroughly.
- Carefully pour 5 ml concentrated H2SO4 along the side of the test tube.
- Acid being heavier will form a layer beneath the sugar solution.
INDICATION:
The formation of a reddish violet ring at the junction of the two liquids indicates the presence of carbohydrates.
RESULT:
Carbohydrates are present.
NOTE:
This test is very sensitive and is given by all the carbohydrates
Precautions:
- Wash the apparatus before and after the experiment.
- Carefully pour the acids along the side of the test tube.
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