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Anthracene

|Section2={{Chembox Properties | C=14 | H=10 | Appearance = Colorless | Odor = Weak aromatic | Density = 1.28 g/cm3 (25 °C) 0.969 g/cm3 (220 °C) | MeltingPtC = 215.76 | MeltingPt_notes = at 760 mmHg | BoilingPtC = 339.9 | BoilingPt_notes = at 760 mmHg | Solubility = 0.022 mg/L (0 °C) 0.044 mg/L (25 °C) 0.287 mg/L (50 °C) 0.00045% w/w (100 °C, 3.9 MPa) | SolubleOther = Soluble in alcohol, (C2H5)2O, acetone, C6H6, CHCl3, CS2 | Solubility1 = 0.076 g/100 g (16 °C) 1.9 g/100 g (19.5 °C) 0.328 g/100 g (25 °C) | Solvent1 = ethanol | Solubility2 = 1.8 g/100 g (19.5 °C) | Solvent2 = methanol | Solubility3 = 0.37 g/100 g | Solvent3 = hexane | Solubility4 = 0.92 g/100 g (16.5 °C) 12.94 g/100 g (100 °C) | Solvent4 = toluene | Solubility5 = 0.732 g/100 g | Solvent5 = carbon tetrachloride | VaporPressure = 0.01 kPa (125.9 °C) 0.1 kPa (151.5 °C) 13.4 kPa (250 °C) | HenryConstant = 0.039 L·atm/mol | LogP = 4.56 | ThermalConductivity = 0.1416 W/m·K (240 °C) 0.1334 W/m·K (270 °C) 0.1259 W/m·K (300 °C) | Viscosity = 0.602 cP (240 °C) 0.498 cP (270 °C) 0.429 cP (300 °C) | LambdaMax = 345.6 nm, 363.2 nm | MagSus = -130·10−6 cm3/mol }} |Section3={{Chembox Structure | CrystalStruct = Monoclinic (290 K) | SpaceGroup = P21/b | PointGroup = C | LattConst_a = 8.562 Å | LattConst_b = 6.038 Å | LattConst_c = 11.184 Å | LattConst_alpha = | LattConst_beta = 124.7 | LattConst_gamma = }} |Section4={{Chembox Thermochemistry | HeatCapacity = 210.5 J/mol·K | Entropy = 207.5 J/mol·K | DeltaHf = 129.2 kJ/mol | DeltaHc = 7061 kJ/mol }} |Section7={{Chembox Hazards | GHSPictograms = | GHSSignalWord = Warning | HPhrases = | PPhrases = | FlashPtC = 121 | FlashPt_ref = | AutoignitionPtC = 540 | AutoignitionPt_ref = | NFPA-H = 2 | NFPA-F = 1 | NFPA-R = 1 | NFPA_ref = | LD50 = 4900 mg/kg (rats, oral) }} }} 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 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 and carbazole. 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. It may also occur in the interstellar medium. More than 20% of the carbon in the universe may be associated with PAHs, including anthracene.

Reactions

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+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.Rickborn, Bruce "The retro-Diels-Alder reaction. Part I. C-C dienophiles" Organic Reactions 1998, vol. 52. Bouas-Laurent, Henri; Desvergne, Jean-Pierre; Castellan, Alain; Lapouyade, Rene "Photodimerization of anthracenes in fluid solution: structural aspects" Chemical Society Reviews (2000), vol. 29, pp. 43-55. Reduction of anthracene with alkali metals yields the deeply colored radical anion salts M+ anthracene− (M = Li, Na, K). Hydrogenation gives 9,10- dihydroanthracene, preserving the aromaticity of the two flanking rings. Chemical oxidation occurs readily, giving anthraquinone, C14H8O2 (below), for example using hydrogen peroxide and vanadyl acetylacetonate.Kimberly D. M. Charleton, Ernest M. Prokopchuk Coordination Complexes as Catalysts: The Oxidation of Anthracene by Hydrogen Peroxide in the Presence of VO(acac)2 Journal of Chemical Education 2011 88 (8), 1155-1157 Anthracene also reacts with dienophile singlet oxygen in a 4+2-cycloaddition ( Diels–Alder reaction):

Uses

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

Niche

Anthracene, a wide band-gap organic semiconductor is used as a scintillator for detectors of high energy photons, electrons and alpha particles. Plastics, such as polyvinyltoluene, can be doped with anthracene to produce a plastic scintillator that is approximately water-equivalent for use in radiation therapy dosimetry. Anthracene's emission spectrum peaks at between 400 nm and 440 nm. It is also used in wood preservatives, insecticides, 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.Conformal Coating 101, https://www.smta.org/chapters/files/UpperMidwest_BTW_Conformal_Coating_June_27th_2012.pdf Anthracene is one of the three components (the other two being potassium perchlorate and sulfur) which are used to produce the black smoke released during a Papal Conclave.Vatican Radio, Briefing by Fr. Federico Lombardi, 03/13/2013, 1 p.m. CET.

Derivatives

A variety of anthracene derivatives find specialized uses. Derivatives having a hydroxyl group are 1-hydroxyanthracene and 2-hydroxyanthracene, homologous to phenol and naphthols, and hydroxyanthracene (also called anthrol, and anthracenol) 1-Hydroxyanthracene NIST datapage 2-Hydroxyanthracene NIST datapage are pharmacologically active. Anthracene may also be found with multiple hydroxyl groups, as in 9,10-dihydroxyanthracene.

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.http://www.cie.iarc.fr/htdocs/monographs/vol32/anthracene.html

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 compounds. Furthermore, it is readily biodegraded in soil. It is especially susceptible to degradation in the presence of light.

See also

References

External links

"green air" © 2007 - Ingo Malchow, Webdesign Neustrelitz
This article based upon the http://en.wikipedia.org/wiki/Anthracene, the free encyclopaedia Wikipedia and is licensed under the GNU Free Documentation License.
Further informations available on the list of authors and history: http://en.wikipedia.org/w/index.php?title=Anthracene&action=history
presented by: Ingo Malchow, Mirower Bogen 22, 17235 Neustrelitz, Germany