Anthraquinone

9,10-Anthraquinone
IUPAC name Anthraquinone
Other names 9,10-anthracenedione, anthradione, 9,10-anthrachinon, anthracene-9,10-quinone, 9,10-dihydro-9,10-dioxoanthracene, Hoelite, Morkit, Corbit
Identifiers
CAS number	84-65-1 Y
ChemSpider	6522
SMILES O=C1c2ccccc2C(=O)c3ccccc13
Properties
Molecular formula	C14H8O2
Molar mass	208.21 g mol−1
Appearance	yellow solid
Melting point	286 °C
Boiling point	379.8 °C
Solubility in water	Insoluble
Hazards
R-phrases	R36/37/38
Flash point	185°C
Related compounds
Related compounds	quinone, anthracene
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Anthraquinone, also called anthracenedione or dioxoanthracene is an aromatic organic compound with formula C₁₄H₈O₂, that can be viewed as a diketone derivative of anthracene (with loss of two double bonds in the latter).

The term usually refers to one specific isomer, 9,10-anthraquinone or 9,10-dioxoanthracene, whose ketone groups are on the central ring. This compound is an important member of the quinone family. It is a building block of many dyes and is industrially used in bleaching pulp for papermaking. It is a yellow highly crystalline solid, poorly soluble in water but soluble in hot organic solvents. For instance, it is almost completely insoluble in ethanol near room temperature but 2.25 g will dissolve in 100 g of boiling ethanol.

Several other anthraquinone isomers are possible, such as 1,2-, 1,4-, and 2,6-anthraquinone, but they are of comparatively minor importance. The term is also used in the more general sense of any compound that can be viewed as an anthraquinone with some hydrogen atoms replaced by other atoms or functional groups. These derivatives include many substances that are technically useful or play important roles in living beings.

Synthesis

9,10-Anthraquinone is obtained industrially by the oxidation of anthracene, a reaction that is localized at the central ring. Chromium(VI) is the typical oxidant. It is also prepared by the Friedel-Crafts reaction of benzene and phthalic anhydride in presence of AlCl₃. The resulting o-benzoylbenzoic acid then undergoes cyclization, forming anthraquinone. This reaction is useful for producing substituted anthraquinones. The Diels-Alder reaction of naphthoquinone and butadiene followed by oxidative dehydrogenation. Lastly, BASF has developed a process that proceeds via the acid-catalyzed dimerization of styrene to give a 1,3-diphenylbutene, which then can be transformed to the anthaquinone.^[1]

It also arises via the Rickert-Alder reaction, a retro-Diels-Alder reaction. In a classic (1905)organic reaction called the Bally-Scholl synthesis, anthraquinone condenses with glycerol forming benzanthrone^[2]. In this reaction, the quinone is first reduced with copper metal in sulfuric acid (converting one ketone group into a methylene group) after which the glycerol is added.

Applications and natural occurrence

Dyestuff precursor

Synthetic dyes are often derived from 9,10-anthraquinone, such as alizarin. Important derivatives are 1-nitroanthraquinone, anthraquinone-1-sulfonic acid, and the dinitroanthraquinone.^[1] Natural pigments that are derivatives of anthraquinone are found, inter alia, in aloe latex, senna, rhubarb, and Cascara buckthorn), fungi, lichens, and some insects.

Selection of anthraquinone dyes. From the left: C.I.Acid Blue 43 an "acid dye" for wool (also called "Acilan Saphirol SE"), C.I. Vat Violet 1, which is applied by transfer printing using sublimation, a blue colorant commonly used in gasoline, and C.I. Disperse Red 60, a so-called vat dye.

Digester additive in papermaking

9,10-Anthraquinone is used as a digester additive in production of paper pulp by alkaline processes, like the Kraft, the alkaline sulfite process or the Soda-AQ processes. The anthraquinone is going through a redox cycle and is giving a catalytic effect. The antraquinone is oxidizing cellulose and thereby protecting it from alkaline degradation (peeling). The anthraquinone is reduced to hydroantraquinone which then can react with lignin. The lignin is degraded and becomes more watersoluble and thereby more easy to wash away from the pulp, while the antraquinone is regenerated. This process gives an increase in yield of pulp, typically 1-3 % and a reduction in kappa number.

Sodium 2-anthraquinonesulfonate (AMS) is a watersoluble anthraquinone derivative that was the first anthraquinone derivative discovered to have a catalytic effect in the alkaline pulping processes^[3].

In the production of hydrogen peroxide

A large industrial application of anthraquinones is for the production of hydrogen peroxide. 2-Ethyl-9,10-anthraquinone or a related alkyl derivatives is used, rather anthraquinone itself.^[4]

Catalytic hydrogen peroxide production with the anthraquinone process

Medicine

Derivatives of 9,10-anthraquinone include many important drugs (collectively called anthracenediones). They include

• laxatives like dantron, emodin, and aloe emodin, and some of the senna glycosides
• antimalarials like rufigallol
• antineoplastics used in the treatment of cancer, like mitoxantrone, pixantrone, and the anthracyclines.

Aloe emodin	Mitoxantrone	Pixantrone

Niche uses

9,10-Anthraquinone is uses as a bird repellant on seeds and as a gas generator in satellite balloons[1].

Natural anthraquinone derivatives tend to have laxative effects. Prolonged use and abuse leads to melanosis coli.^[5][6]

See also

• Benzoquinone
• Naphthoquinone
• Hydroxyanthraquinone

References

External links

• National Pollutant Inventory - Polycyclic Aromatic Hydrocarbon Fact Sheet
• Molecules Spontaneously Form Honeycomb Network