Liebermann–Burchard test

The Liebermann - Burchard reaction is a name reaction for the detection of sterols. Classically, a fat extract with acetic acid, acetic anhydride and concentrated sulfuric acid is added under ice-cooling. The resulting Pentaenylkation is colored depending on the variant of the tests and the structure of the sterol green or red. It can be used as a qualitative detection reaction or be measured photometrically at 620 nm. In place of the sulfur trioxide and iron (III) cations may be used as the oxidant.

The reaction had a broad application in the 20th century and is still today a reference method. It was first time in 1885 by chemist Carl Liebermann ( 1842-1914 ) and later described by the physician Hans Burchard Richard Ferdinand ( 1864-1900 ) developed for the quantitative determination of cholesterol. Modern study of the structure elucidation shed light on the reaction mechanism does not Cholestadiene, i- steroids or cholesterol - containing dimers as first thought. Instead, cholesterol and its acetate and sulfate derivatives is sulfonated at different places where often skeletal rearrangements occur. The elimination of sulfonic acid groups as sulfurous acid provides new double bonds. A repetition leads to polyenes and ultimately to aromatic steroids.