Molisch sample
Molisch sample using D- glucose as an example . The 5-hydroxymethylfurfural formed by dehydration reacts with two equivalents of 1-naphthol in an acidic medium to form a mesomerism-stabilized violet dye.
The Molisch test (or Molisch reaction) is a general detection of carbohydrates . It goes back to the Austrian botanist Hans Molisch (1856–1937).
Execution and response
Molisch reagent (solution of α-naphthol in ethanol ) is added to a dilute solution of ribose (or another monosaccharide ) and the reaction mixture is then covered with concentrated sulfuric acid . A purple ring forms at the interface.
Under the action of a strong acid, such as. B. concentrated sulfuric acid , is formed from pentoses and hexoses by intramolecular dehydration furfural or 5-hydroxymethylfurfural , which condenses with α-naphthol to a violet dye. This dye is formed by all compounds that contain carbohydrates, including nucleic acids and glycoproteins , for example .
literature
- MUTSUKO OHTA, MASATAKE IWASAKI, KEIKI KOUNO, YO UEDA: Mechanism of the Molisch reaction .. In: CHEMICAL & PHARMACEUTICAL BULLETIN. 33, 1985, p. 2862, doi : 10.1248 / cpb.33.2862 .
Individual evidence
- ↑ Hans Molisch, in: Monatsh. Chem. (1886), Vol. 7, p. 198.
- ^ Ulrich Flörke and Robert Wolff: Chemistry course topics , Volume 2, Organic Chemistry and Biochemistry, Bonn 1982, ISBN 3-427-43121-5 , pp. 6/10.