Anthraquinone, also called anthracenedione or dioxoanthracene, is an aromatic organic compound with formula . Several isomers exist but these terms usually refer to 9,10-anthraquinone (IUPAC: 9,10-dioxoanthracene) wherein the keto groups are located on the central ring. It is used as a digester additive to wood pulp for papermaking. Many anthraquinone derivatives are generated by organisms or synthesised industrially for use as dyes, pharmaceuticals, and catalysts. Anthraquinone 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. It is found in nature as the rare mineral hoelite.
There are several current industrial methods to produce 9,10-anthraquinone:
It also arises via the RickertâÂÂAlder reaction, a retro-DielsâÂÂAlder reaction.
Hydrogenation gives dihydroanthraquinone (anthrahydroquinone). Reduction with copper gives anthrone. Sulfonation with oleum gives anthroquinone-1-sulfonic acid, which reacts with sodium chlorate to give 1-chloroanthraquinone.
Anthraquinone itself has few direct applications except as a precursor to some dyes. It has been used as a bird repellant on seeds, and as a gas generator in satellite balloons. It has also been mixed with lanolin and used as a wool spray to protect sheep flocks against kea attacks in New Zealand. Anthraquinone derivatives are more useful.
Several other isomers of anthraquinone exist, including the 1,2-, 1,4-, and 2,6-anthraquinones. They are of minor importance compared to 9,10-anthraquinone.
Anthraquinone has no recorded , probably because it is so insoluble in water.
In terms of metabolism of substituted anthraquinones, the enzyme encoded by the gene UGT1A8 has glucuronidase activity with many substrates including anthraquinones.