Molisch Test

Molisch Test:


Shows positive test for:

All carbohydrates, Monosaccharides,disaccarides,and polysacarides,shouhd give a positive reaction.nucleic acids and glycoproteines also give a positive reaction.

Molishs reagent:

2g 1-naphthol dissolved in 20 ml etoh 95%

Reactions:

all these compounds are eventually hydrolysed to monosacharides by strongmineral acids.
The test reagent dehydrates pentoses to form furfural and dehydrates hexoses to form 5-hydroxymethyl furfural .The furfurals further react with -naphthol present in the test reagent to produce a purple product.


Procedure:

Two ml of a sample solution is placed in a test tube. Two drops of the Molisch reagent (a solution of -napthol in 95% ethanol) is added. The solution is then poured slowly into a tube containing two ml of concentrated sulfuric acid so that two layers form.

A positive test is indicated by:

The formation of a purple product at the interface of the two layers.