Molisch Test Lab Report

The presence of carbohydrates in a solution can be determined by a qualitative test of Molisch test. Molisch test is a general, sensitive chemical test and positive for all kinds of carbohydrates which in free form or in combined form. The test is based on the dehydration of the carbohydrate by concentrated sulfuric acid to produce an aldehyde which condenses with two molecules of phenol, resulting in a coloured compound.
Molisch reagent is a solution of α-napthol in 95% ethanol. The aldehydes produced are pentoses and hexoses which can derive to furfural and hydroxymethyl furfural respectively. The Molisch reagent further reacts with furfural to yield a coloured product which is a deep violet ring at the interface of two layers. The reaction occur at the junction where both concentrated sulfuric acid and test solution meet since the concentrated sulfuric acid is denser than the test solution.
In this experiment, all the test solutions show a positive test with Molisch reagent and concentrated sulfuric acid to form a violet ring at the interface of two layers. This is because the samples used in this experiment are maltose, glucose and starch which are considered as carbohydrate that should give a positive reaction. Monosaccharides give a rapid positive test compare to disaccharides and polysaccharides which will react slower. Therefore, the
(Food Tests - Benedict's Test for Reducing Sugars) Reducing sugars contain an aldehyde functional group or ketone group in open chain form which can be converted into aldehyde easily. Both Fehling’s test and Benedict’s test are used to determine and identify the presences of reducing sugars in a solution. All monosaccharides are reducing sugars as well as some easily hydrolyzed disaccharides as they possess the free aldehyde or ketone group to be