Molisch’s Test

                                                                             Primary Concept                                                             
                                               Molisch’s Test is a sensitive chemical test for all carbohydrates, and some compounds containing carbohydrates in a combined form, based on the dehydration of the carbohydrate by sulfuric acid to produce an aldehyde (either furfural or a derivative), which then condenses with the phenolic structure resulting in a red or purple colored compound.


Procedure:

- Apply this test two different carbohydrate solutions of your own choice, preferably to one monosaccharide and one polysaccharide.

- Place 2 mL of a known carbohydrate solution in a test tube, add 1 drop of Molisch’s reagent (10% α-naphthol in ethanol).

- Pour 1-2 mL of conc. H2SO4 down the side of the test tube, so that it forms a layer at the bottom of the tube.

- Observe the color at the interface between two layers and compare your result with a control test.

 A brown color due to charring must be ignored and the test should be repeated with a more dilute sugar solution.

Questions:
 Write the reaction step(s) involved in this test?
 Give an example of a protein structure that would give positive test with Molisch’s Reagent.