Anthraquinone, also called anthracenedione or dioxoanthracene, is an aromatic organic compound with formula C Isomers include various quinone derivatives. The term anthraquinone, however refers to the isomer, 9,10-anthraquinone (IUPAC: 9,10-dioxoanthracene) wherein the keto groups are located on the central ring. It is a building block of many dyes and is used in bleaching pulp for papermaking. It is a yellow, highly crystalline solid, poorly soluble in water but soluble in hot organic solvents. It is almost completely insoluble in ethanol near room temperature but 2.25 g will dissolve in 100 g of boiling ethanol.
Anthraquinone dyes are a shared structural element as an anthraquinone unit comprising an abundant group of dyes. Anthraquinone itself is colorless, but red to blue dyes are obtained by introducing electron donor groups such as hydroxy or amino groups into position 1, 4, 5 or 8. Anthraquinone dyes are structurally related and classified as indigo dyes in the group of carbonyl dyes.
Synthetic dyes as well as natural dyes can be found in this group of members. The anthraquinone dyes are by biting and in vats, but also in reactive and dispersed dyes. They are characterized by very good resistance to light The plant origin of one of the most important anthraquinone dyes is alizarin, which is extracted from the madder of dyer (Rubia tinctorum). Alizarin is a number of structurally related dyes that use alizarin dyes (sometimes synonymous with anthraquinone dyes). It is the first natural dye for which industrial synthesis was developed in 1869. Anthraquinone dyes include insect dyes derived from winged insects such as carminic acid, kermesic acid and laccainic acids. The main component of carmine dye is carminic acid, used for example, as an approved food coloring E 12