The Baeyer–Drewson indigo synthesis (1882) is an
organic reaction
Organic reactions are chemical reactions involving organic compounds. The basic organic chemistry reaction types are addition reactions, elimination reactions, substitution reactions, pericyclic reactions, rearrangement reactions, Mechanistic Organ ...
in which
indigo
Indigo is a deep color close to the color wheel blue (a primary color in the RGB color space), as well as to some variants of ultramarine, based on the ancient dye of the same name. The word "indigo" comes from the Latin word ''indicum'', m ...
is prepared from
2-nitrobenzaldehyde and
acetone
Acetone (2-propanone or dimethyl ketone), is an organic compound with the formula . It is the simplest and smallest ketone (). It is a colorless, highly volatile and flammable liquid with a characteristic pungent odour.
Acetone is miscib ...
The reaction was developed by von Baeyer in 1880 to produce the first synthetic indigo at laboratory scale. This procedure is not used at industrial scale.
The reaction is classified as an
aldol condensation
An aldol condensation is a condensation reaction in organic chemistry in which two carbonyl moieties (of aldehydes or ketones) react to form a β-hydroxyaldehyde or β-hydroxyketone (an aldol reaction), and this is then followed by dehydration to ...
. As a practical route to indigo, this method was displaced by routes from
aniline
Aniline is an organic compound with the formula C6 H5 NH2. Consisting of a phenyl group attached to an amino group, aniline is the simplest aromatic amine
In organic chemistry, an aromatic amine is an organic compound consisting of an aroma ...
.
[Elmar Steingruber "Indigo and Indigo Colorants" Ullmann's Encyclopedia of Industrial Chemistry 2004, Wiley-VCH, Weinheim. ]
Mechanism
Note
In the English literature this reaction is usually called Baeyer–Drews
on reaction, although the author of the original paper was called Drews
en.
References
External links
Lab ManualLab-synthesis of indigo
{{DEFAULTSORT:Baeyer-Drewson indigo synthesis
Nitrogen heterocycle forming reactions
Organic reactions
Name reactions