Molisch Test Lab Report

Molisch test is a general, sensitive chemical test for the presence of carbohydrates. This test is based on the dehydration of the carbohydrate by concentrated sulfuric acid or hydrochloric acid to produce an aldehyde, which condenses with two molecules of phenol, resulting in a colored compound.

The test reagent dehydrates pentoses to form furfural and dehydrates hexoses to form 5-hydroxymethyl furfural. The furfurals further react with Molisch reagent (α-naphthol) to yield a colored product, generally a purple ring at the interface of the two layers. The purple-coloured compound appears as a ring layer at the interface between the sulphuric acid and test solution. The sulphuric acid is denser than the test solution and therefore the reaction will occur at the junction where both substances meet.

All carbohydrates – monosaccharides, disaccharides, and polysaccharides should give a positive reaction. Monosaccharides give a rapid positive test while disaccharides and polysaccharides react slower. Because all of the sample in this experiment

The reaction involves the formation of Copper (II) oxide which is reduced to Copper (I) oxide in the presence of aldehydes. Wheareas Benedict 's solution is a single solution of Copper (II) sulfate dissolved in a Sodium carbonate/Sodium citrate buffer. This reacts with the electrons from the ketone or aldehyde group of the free reactive carbonyl group on the carbohydrate to form cuprous oxide (a red-brown precipitate). This precipitate is formed due to the reduction of the Cu2+ ions to Cu+ ions that form Copper (I) oxide which is a brick-red precipitate. In the process, the carbohydrate is oxidized. The samples in the experiment, fructose and maltose show positive test that brick red precipitate formed from the blue solution.Whereas sucrose has no change in the