Fluorescence of Anthracene under UV light

Anthracene is a solid polycyclic aromatic hydrocarbon (PAH) of formula C₁₄H₁₀, consisting of three fused benzene rings. It is a component of coal tar. Anthracene is used in the production of the red

dye A dye is a colored substance that chemically bonds to the substrate to which it is being applied. This distinguishes dyes from pigments which do not chemically bind to the material they color. Dye is generally applied in an aqueous solution an ...

alizarin and other dyes. Anthracene is colorless but exhibits a blue (400–500 nm peak) fluorescence under ultraviolet radiation.

Occurrence and production

Coal tar, which contains around 1.5% anthracene, remains a major source of this material. Common impurities are

phenanthrene Phenanthrene is a polycyclic aromatic hydrocarbon (PAH) with formula C14H10, consisting of three fused benzene rings. It is a colorless, crystal-like solid, but can also appear yellow. Phenanthrene is used to make dyes, plastics and pesticides, e ...

and carbazole. The mineral form of anthracene is called freitalite and is related to a coal deposit. A classic laboratory method for the preparation of anthracene is by cyclodehydration of o-methyl- or o-methylene-substituted diarylketones in the so-called

Elbs reaction The Elbs reaction is an organic reaction describing the pyrolysis of an ortho methyl substituted benzophenone to a condensed polyaromatic. The reaction is named after its inventor, the German chemist Karl Elbs, also responsible for the Elbs oxid ...

, for example from ''o''-tolyl phenyl ketone.

Reactions

Reduction

Reduction of anthracene with alkali metals yields the deeply colored radical anion salts M⁺ nthracenesup>− (M = Li, Na, K). Hydrogenation gives 9,10- dihydroanthracene, preserving the aromaticity of the two flanking rings.

Cycloadditions

Anthracene photodimerizes by the action of UV light: : The dimer, called dianthracene (or sometimes paranthracene), is connected by a pair of new carbon-carbon bonds, the result of the +4 cycloaddition. It reverts to anthracene thermally or with UV irradiation below 300 nm. Substituted anthracene derivatives behave similarly. The reaction is affected by the presence of oxygen. Anthracene also reacts with dienophile

singlet oxygen Singlet oxygen, systematically named dioxygen(singlet) and dioxidene, is a gaseous inorganic chemical with the formula O=O (also written as or ), which is in a quantum state where all electrons are spin paired. It is kinetically unstable at ambie ...

in a +2cycloaddition (

Diels–Alder reaction In organic chemistry, the Diels–Alder reaction is a chemical reaction between a conjugated diene and a substituted alkene, commonly termed the dienophile, to form a substituted cyclohexene derivative. It is the prototypical example of a peric ...

): :

With electrophiles

Chemical oxidation occurs readily, giving anthraquinone, C₁₄H₈O₂ (below), for example using hydrogen peroxide and vanadyl acetylacetonate. : Electrophilic substitution of anthracene occurs at the 9 position. For example, formylation affords 9-anthracenecarboxaldehyde. Substitution at other positions is effected indirectly, for example starting with anthroquinone. Bromination of anthracene gives 9,10-dibromoanthracene.

Uses

Anthracene is converted mainly to anthraquinone, a precursor to dyes.Collin, Gerd; Höke, Hartmut and Talbiersky, Jörg (2006) "Anthracene" in ''Ullmann's Encyclopedia of Industrial Chemistry'', Wiley-VCH, Weinheim.

Niche

Anthracene, a wide band-gap organic semiconductor is used as a

scintillator A scintillator is a material that exhibits scintillation, the property of luminescence, when excited by ionizing radiation. Luminescent materials, when struck by an incoming particle, absorb its energy and scintillate (i.e. re-emit the absorbed ...

for detectors of high energy photons, electrons and alpha particles. Plastics, such as

polyvinyltoluene Polyvinyltoluene (PVT, polyvinyl toluene) is a synthetic polymer of alkylbenzenes with a linear formula H2CH(C6H4CH3). Commercial vinyl toluene is a mixture of methyl styrene isomers File:Chemical_formula_for_polyvinyl_tolulene.png, chemical for ...

, can be doped with anthracene to produce a plastic

that is approximately water-equivalent for use in radiation therapy dosimetry. Anthracene's

emission spectrum The emission spectrum of a chemical element or chemical compound is the spectrum of frequencies of electromagnetic radiation emitted due to an electron making a atomic electron transition, transition from a high energy state to a lower energy st ...

peaks at between 400 nm and 440 nm. It is also used in wood preservatives,

insecticide Insecticides are substances used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. Insecticides are used in agriculture, medicine, industry and by consumers. Insecticides are claimed to b ...

s, and coating materials. Anthracene is commonly used as a UV tracer in conformal coatings applied to printed wiring boards. The anthracene tracer allows the conformal coating to be inspected under UV light.

Derivatives

A variety of anthracene derivatives find specialized uses. Derivatives having a

hydroxyl group In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydroxy g ...

are 1-hydroxyanthracene and 2-hydroxyanthracene, homologous to phenol and naphthols, and hydroxyanthracene (also called anthrol, and anthracenol) are

pharmacologically Pharmacology is a branch of medicine, biology and pharmaceutical sciences concerned with drug or medication action, where a drug may be defined as any artificial, natural, or endogenous (from within the body) molecule which exerts a biochemica ...

active. Anthracene may also be found with multiple hydroxyl groups, as in

9,10-dihydroxyanthracene 9,10-Dihydroxyanthracene is an organic compound with the formula (C6H4CHOH)2. It is the hydroquinone form of 9,10-anthraquinone (AQ). It formed when AQ is hydrogenated. It is easily dissolved in alkaline solutions and is often called ''soluble an ...

Occurrence

Anthracene, as many other polycyclic aromatic hydrocarbons, is generated during combustion processes. Exposure to humans happens mainly through tobacco smoke and ingestion of food contaminated with combustion products.

Toxicology

Many investigations indicate that anthracene is noncarcinogenic: "consistently negative findings in numerous in vitro and in vivo genotoxicity tests". Early experiments suggested otherwise because crude samples were contaminated with other polycyclic aromatic hydrocarbons. Furthermore, it is readily biodegraded in soil. It is especially susceptible to degradation in the presence of light.

References

Cited sources

External links

Image
of anthracene crystals *
IARC – Monograph 32

* ttps://web.archive.org/web/20110122105255/http://echa.europa.eu/home_en.asp European Chemicals Agency – ECHA* {{Authority control Organic semiconductors Phosphors and scintillators IARC Group 3 carcinogens Anthracenes Ionising radiation detectors Acenes PBT substances Polycyclic aromatic hydrocarbons