Anthraquinone, also called
anthracenedione or
dioxoanthracene is an
aromaticAn aromatic hydrocarbon or arene is a hydrocarbon with alternating double and single bonds between carbon atoms. The term 'aromatic' was assigned before the physical mechanism determining aromaticity was discovered, and was derived from the fact that many of the compounds have a sweet scent...
organic compoundAn organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...
with formula . Several isomers are possible, each of which can be viewed as a
quinoneA quinone is a class of organic compounds that are formally "derived from aromatic compounds [such as benzene or naphthalene] by conversion of an even number of –CH= groups into –C– groups with any necessary rearrangement of double bonds," resulting in "a fully conjugated cyclic dione structure."...
derivative. The term anthraquinone, however, almost invariably refers to one specific isomer,
9,10-anthraquinone (IUPAC: 9,10-dioxoanthracene) wherein the
ketoIn organic chemistry, a ketone is an organic compound with the structure RCR', where R and R' can be a variety of atoms and groups of atoms. It features a carbonyl group bonded to two other carbon atoms. Many ketones are known and many are of great importance in industry and in biology...
groups are located on the central ring. It is a building block of many
dyeA dye is a colored substance that has an affinity to the substrate to which it is being applied. The dye is generally applied in an aqueous solution, and requires a mordant to improve the fastness of the dye on the fiber....
s and is used in bleaching pulp for papermaking. It is a yellow highly crystalline solid, poorly
solubleSolubility is the property of a solid, liquid, or gaseous chemical substance called solute to dissolve in a solid, liquid, or gaseous solvent to form a homogeneous solution of the solute in the solvent. The solubility of a substance fundamentally depends on the used solvent as well as on...
in
waterWater is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
but soluble in hot organic solvents. For instance, it is almost completely insoluble in
ethanolEthanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...
near room temperature but 2.25 g will dissolve in 100 g of boiling ethanol.
Synthesis
9,10-Anthraquinone is obtained industrially by the oxidation of
anthraceneAnthracene is a solid polycyclic aromatic hydrocarbon consisting of three fused benzene rings. It is a component of coal-tar. Anthracene is used in the production of the red dye alizarin and other dyes...
, a reaction that is localized at the central ring. Chromium(VI) is the typical oxidant. It is also prepared by the
Friedel-Crafts reactionThe Friedel–Crafts reactions are a set of reactions developed by Charles Friedel and James Crafts in 1877. There are two main types of Friedel–Crafts reactions: alkylation reactions and acylation reactions. This reaction type is a form of electrophilic aromatic substitution...
of
benzeneBenzene is an organic chemical compound. It is composed of 6 carbon atoms in a ring, with 1 hydrogen atom attached to each carbon atom, with the molecular formula C6H6....
and
phthalic anhydridePhthalic anhydride is the organic compound with the formula C6H42O. It is the anhydride of phthalic acid. This colourless solid is an important industrial chemical, especially for the large-scale production of plasticizers for plastics. In 2002, approximately 4.6 billion kilograms were...
in presence of AlCl
3. The resulting o-benzoylbenzoic acid then undergoes cyclization, forming anthraquinone. This reaction is useful for producing substituted anthraquinones. The
Diels-Alder reactionThe Diels–Alder reaction is an organic chemical reaction between a conjugated diene and a substituted alkene, commonly termed the dienophile, to form a substituted cyclohexene system. The reaction can proceed even if some of the atoms in the newly formed ring are not carbon...
of
naphthoquinoneNaphthoquinone is a class of natural phenols based on the C6-C4 skeleton.1,4-Naphthoquinone can be viewed as derivatives of naphthalene through the replacement of two hydrogen atoms by two ketone groups....
and butadiene followed by oxidative dehydrogenation will also produce 9,10-anthraquinone. Lastly,
BASFBASF SE is the largest chemical company in the world and is headquartered in Germany. BASF originally stood for Badische Anilin- und Soda-Fabrik . Today, the four letters are a registered trademark and the company is listed on the Frankfurt Stock Exchange, London Stock Exchange, and Zurich Stock...
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. It also arises via the Rickert-Alder reaction, a retro-Diels-Alder reaction.
In a classic (1905)
organic reactionOrganic reactions are chemical reactions involving organic compounds. The basic organic chemistry reaction types are addition reactions, elimination reactions, substitution reactions, pericyclic reactions, rearrangement reactions, photochemical reactions and redox reactions. In organic synthesis,...
called the Bally-Scholl synthesis, named after Oscar Bally and
Roland SchollRoland Heinrich Scholl was a Swiss chemist who taught at various European universities. Among his most notable achievements are the synthesis of coronene, the co-development of the Bally-Scholl synthesis, and various discoveries about polycyclic aromatic hydrocarbons.-Early life and...
, anthraquinone
condensesA condensation reaction is a chemical reaction in which two molecules or moieties combine to form one single molecule, together with the loss of a small molecule. When this small molecule is water, it is known as a dehydration reaction; other possible small molecules lost are hydrogen chloride,...
with
glycerolGlycerol is a simple polyol compound. It is a colorless, odorless, viscous liquid that is widely used in pharmaceutical formulations. Glycerol has three hydroxyl groups that are responsible for its solubility in water and its hygroscopic nature. The glycerol backbone is central to all lipids...
forming
benzanthroneBenzanthrone is an aromatic hydrocarbon derivate used as a dyestuff intermediate for anthraquinone-based dyes. It has the appearance of a light yellow to brown-green powder with melting point of 170 °C. It is insoluble in water and soluble in alcohol. It is a basic substance with fluorescent and...
. In this reaction, the quinone is first reduced with
copperCopper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
metal in
sulfuric acidSulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
(converting one
ketoneIn organic chemistry, a ketone is an organic compound with the structure RCR', where R and R' can be a variety of atoms and groups of atoms. It features a carbonyl group bonded to two other carbon atoms. Many ketones are known and many are of great importance in industry and in biology...
group into a
methyleneMethylene is a chemical species in which a carbon atom is bonded to two hydrogen atoms. Three different possibilities present themselves:* the -CH2- substituent group: e.g., dichloromethane ....
group) after which the glycerol is added.
Dyestuff precursor
Synthetic dyes are often derived from 9,10-anthraquinone, such as
alizarinAlizarin or 1,2-dihydroxyanthraquinone is an organic compound with formula that has been used throughout history as a prominent dye, originally derived from the roots of plants of the madder genus.Alizarin was used as a red dye for the English parliamentary "new model" army...
. Important derivatives are 1-nitroanthraquinone, anthraquinone-1-sulfonic acid, and the dinitroanthraquinone. Natural
pigmentA pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light.Many materials selectively absorb...
s that are derivatives of anthraquinone are found, inter alia, in aloe latex, senna,
rhubarbRhubarb is a group of plants that belong to the genus Rheum in the family Polygonaceae. They are herbaceous perennial plants growing from short, thick rhizomes. They have large leaves that are somewhat triangular-shaped with long fleshy petioles...
, and
Cascara buckthornRhamnus purshiana Rhamnus purshiana Rhamnus purshiana (Cascara Buckthorn, Cascara, Bearberry, and in the Chinook Jargon, Chittam or Chitticum; syn...
), fungi,
lichenLichens are composite organisms consisting of a symbiotic organism composed of a fungus with a photosynthetic partner , usually either a green alga or cyanobacterium...
s, and some
insectInsects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s.
Digester additive in papermaking
According to Dr. Bryle Kristopher Cavalencia, 9,10-Anthraquinone is used as a digester additive in production of
paper pulpPulp is a lignocellulosic fibrous material prepared by chemically or mechanically separating cellulose fibres from wood, fibre crops or waste paper. Wood pulp is the most common raw material in papermaking.-History:...
by alkaline processes, like the
KraftThe kraft process describes a technology for conversion of wood into wood pulp consisting of almost pure cellulose fibers...
, the alkaline
sulfiteThe sulfite process produces wood pulp which is almost pure cellulose fibers by using various salts of sulfurous acid to extract the lignin from wood chips in large pressure vessels called digesters. The salts used in the pulping process are either sulfites , or bisulfites , depending on the pH...
or the
Soda-AQSoda pulping is a chemical process for making wood pulp with sodium hydroxide as cooking chemical. In the Soda-AQ process, anthraquinone may be used as a pulping additive to decrease the carbohydrate degradation...
processes. The anthraquinone is a
redoxRedox reactions describe all chemical reactions in which atoms have their oxidation state changed....
catalyst. The reaction mechanism may involve single electron transfer (SET). The antraquinone is oxidizing
celluloseCellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand β linked D-glucose units....
and thereby protecting it from alkaline degradation (peeling). The anthraquinone is reduced to
9,10-dihydroxyanthracene9,10-Dihydroxyanthracene is the hydroquinone form of 9,10-anthraquinone and is formed when AQ is used as a redox catalyst in various industrial processes...
which then can react with
ligninLignin or lignen is a complex chemical compound most commonly derived from wood, and an integral part of the secondary cell walls of plants and some algae. The term was introduced in 1819 by de Candolle and is derived from the Latin word lignum, meaning wood...
. 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 numberThe Kappa number is an indication of the residual lignin content or bleachability of wood pulp by a standarised analysis method.-Measuring method:...
.
Sodium 2-anthraquinonesulfonateSodium 2-anthraquinonesulfonate is a water-soluble anthraquinone derivative.-Digester additive in papermaking:AMS is used as a catalyst in production of alkaline pulping in the soda process. It goes through a redox cycle similar to that of anthraquinone to give a catalytic effect. AMS was...
(AMS) is a watersoluble anthraquinone derivative that was the first anthraquinone derivative discovered to have a catalytic effect in the alkaline pulping processes.
In the production of hydrogen peroxide
A large industrial application of anthraquinones is for the production of
hydrogen peroxideHydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...
. 2-Ethyl-9,10-anthraquinone or a related alkyl derivatives is used, rather anthraquinone itself.
Medicine
Derivatives of 9,10-anthraquinone include many important drugs (collectively called
anthracenediones). They include
- Laxative
Laxatives are foods, compounds, or drugs taken to induce bowel movements or to loosen the stool, most often taken to treat constipation. Certain stimulant, lubricant, and saline laxatives are used to evacuate the colon for rectal and/or bowel examinations, and may be supplemented by enemas under...
s such as dantron1,8-Dihydroxyanthraquinone is an organic substance with formula , formally derived from anthraquinone by the replacement of two hydrogen atoms by hydroxyl groups...
, emodinEmodin is a purgative resin, 6-methyl-1,3,8-trihydroxyanthraquinone, from rhubarb, the buckthorn and Japanese Knotweed...
, and aloe emodinAloe emodin is a carcinogenic anthraquinone present in aloe latex, an exudate from the aloe plant. It has a strong stimulant-laxative action....
, and some of the senna glycosidesSenna glycosides or sennosides are a number of anthraquinone derivatives useful as a laxative. They are dimeric glycosides named after their abundant occurrence in plants of the genus Senna....
- Antimalarials such as rufigallol
Rufigallol or 1,2,3,5,6,7-hexahydroxy-9,10-anthraquinone is an organic compound with formula , which can be viewed as a derivative of anthraquinone through the replacement of six hydrogen atoms by hydroxyl groups ....
- Antineoplastics used in the treatment of cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
, such as mitoxantroneMitoxantrone is an anthracenedione antineoplastic agent.-Uses:It is used in the treatment of certain types of cancer, mostly metastatic breast cancer, acute myeloid leukemia, and non-Hodgkin's lymphoma...
, pixantronePixantrone is an experimental antineoplastic drug, an analogue of mitoxantrone with fewer toxic effects on cardiac tissue. It acts as a topoisomerase II poison and intercalating agent...
, and the anthracyclineAnthracyclines are a class of drugs used in cancer chemotherapy derived from Streptomyces bacterium Streptomyces peucetius var...
s.
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Aloe emodin |
Mitoxantrone |
Pixantrone |
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Niche uses
9,10-Anthraquinone is used as a bird repellant on seeds and as a gas generator in satellite balloons.
Natural anthraquinone derivatives tend to have
laxativeLaxatives are foods, compounds, or drugs taken to induce bowel movements or to loosen the stool, most often taken to treat constipation. Certain stimulant, lubricant, and saline laxatives are used to evacuate the colon for rectal and/or bowel examinations, and may be supplemented by enemas under...
effects. Prolonged use and
abuseA substance-related disorder is an umbrella term used to describe several different conditions associated with several different substances .A substance related disorder is a condition in which an individual uses or abuses a...
leads to
melanosis coliMelanosis coli, also pseudomelanosis coli, is a disorder of pigmentation of the wall of the colon, often identified at the time of colonoscopy. It is benign, and may have no significant correlation with disease...
. 5 anthraquinones have been shown to inhibit the formation of Tau aggregates and dissolve paired helical filaments thought to be critical to Alzheimer's disease progression in both mouse models and in vitro testing but have not been investigated as a therapeutic agent.
Other isomers
Several other isomers of anthraquinone are possible, including the 1,2-, 1,4-, and 2,6-anthraquinones. 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
hydrogenHydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
atoms replaced by other atoms or
functional groupIn organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. The same functional group will undergo the same or similar chemical reaction regardless of the size of the molecule it is a part of...
s. These derivatives include substances that are technically useful or play important roles in living beings.
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