Anthracene

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Anthracene[1]
Anthracene
Anthracene 3D
Identifiers
CAS number 120-12-7 YesY
PubChem 8418
ChemSpider 8111 YesY
UNII EH46A1TLD7 YesY
DrugBank DB07372
KEGG C14315 YesY
ChEBI CHEBI:35298 YesY
ChEMBL CHEMBL333179 YesY
Jmol-3D images Image 1
Image 2
Properties
Molecular formula C14H10
Molar mass 178.23 g mol−1
Appearance Colorless
Density 1.25 g/cm³ at 19.85 °C, Solid
0.969 g/cm³ at 220 °C, liquid
Melting point 218 °C (424 °F; 491 K)
Boiling point 340 °C (644 °F; 613 K)
Solubility in water insoluble
Solubility methanol: 0.0908 g/100 mL
hexane: 0.164 g/100 mL
Hazards
EU classification Dangerous for the Environment
Flash point 121 °C (250 °F; 394 K)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 YesY (verify) (what is: YesY/N?)
Infobox references

Anthracene is a solid polycyclic aromatic hydrocarbon 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 light.[2]


Occurrence[edit]

Coal tar contains around 1.5% anthracene and remains a major source of this material.

In 2010, a strong absorption band of anthracene was observed along a line of sight to a star in the open cluster IC 348, and this may be associated with an intervening molecular cloud.[3] More than 20% of the carbon in the universe may be associated with PAHs, including anthracene.[4]

Production[edit]

Commercial anthracene is obtained from coal tar, common impurities being 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.

Reactions[edit]

Anthracene photodimerizes by the action of UV light:

Anthracene dimer

The dimer is connected by a pair of new carbon-carbon bonds, the result of the [4+4] cycloaddition. The dimer reverts to anthracene thermally or with UV irradiation below 300 nm. The reversible dimerization and the photochromic properties of anthracenes are the basis of potential applications. Substituted anthracene derivatives behave similarly. The reaction is affected by the presence of oxygen.

In general, reduction of anthracene yields 9,10-dihydroanthracene (destroying the aromaticity of the center ring) rather than 1,4-dihydroanthracene (which would destroy the aromaticity of one of the terminal rings). This preference for reduction at the 9 and 10 positions is explained by the fact that aromatic stabilization energy is directly correlated with the number of conjugated pi bonds in an aromatic system. Since 9,10-dihydroanthracene in essence preserves two "benzene" rings (a total of 6 conjugated pi bonds), whereas the 1,4-isomer preserves only one and a half such rings (a total of 5 pi bonds); the latter is not the thermodynamically favorable product. Likewise, electrophilic substitution occurs at the "9" and "10" positions of the center ring.

Oxidation occurs readily, giving anthraquinone, C14H8O2 (below), for example using hydrogen peroxide and vanadyl acetylacetonate.[5]

Anthraquione

Anthracene will also react with the dienophile singlet oxygen in a [4+2]-cycloaddition (Diels–Alder reaction):

Diels alder reaction of anthracene with singlet oxygen

Uses[edit]

Anthracene is converted mainly to anthroquinone, a precursor to dyes.[6]

Anthracene is an organic semiconductor. It 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.[citation needed]

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.[7]

Derivatives[edit]

A variety of anthracene derivatives find niche uses. Derivatives having a hydroxyl group are 1-hydroxyanthracene and 2-hydroxyanthracene, homologous to phenol and naphthols, and hydroxyanthracene (also called anthrol, and anthracenol)[8][9] are pharmacologically active. Anthracene may also be found with multiple hydroxyl groups, as in 9,10-dihydroxyanthracene.

Toxicology[edit]

Unlike many other polycyclic aromatic hydrocarbons (PAH), anthracene is not classified as carcinogenic as listed by OSHA.[10] Anthracene, as many other PAHs, is generated during combustion processes: Exposure to humans happens mainly through tobacco smoke and ingestion of food contaminated with combustion products.[11]

See also[edit]

References[edit]

  1. ^ NIST Chemistry WebBook Anthracene
  2. ^ Jonathan Lindsey and coworkers. "Anthracene". PhotochemCAD. Retrieved 20 February 2014. 
  3. ^ Iglesias-Groth, S.; Manchado, A.; Rebolo, R.; Gonzalez Hernandez, J. I.; Garcia-Hernandez, D. A.; Lambert, D. L. (May 2010). A search for interstellar anthracene toward the Perseus anomalous microwave emission region. arXiv:1005.4388. Bibcode:2010MNRAS.407.2157I. doi:10.1111/j.1365-2966.2010.17075.x. 
  4. ^ Hoover, Rachel (February 21, 2014). "Need to Track Organic Nano-Particles Across the Universe? NASA's Got an App for That". NASA. Retrieved February 22, 2014. 
  5. ^ Coordination Complexes as Catalysts: The Oxidation of Anthracene by Hydrogen Peroxide in the Presence of VO(acac)2 Kimberly D. M. Charleton, Ernest M. Prokopchuk Journal of Chemical Education 2011 88 (8), 1155-1157 doi:10.1021/ed100843a
  6. ^ Gerd Collin, Hartmut Höke and Jörg Talbiersky "Anthracene" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2006. doi:10.1002/14356007.a02_343.pub2
  7. ^ Vatican Radio, Briefing by Fr. Federico Lombardi, 03/13/2013, 1 p.m. CET.
  8. ^ 1-Hydroxyanthracene NIST datapage
  9. ^ 2-Hydroxyanthracene NIST datapage
  10. ^ MSDS
  11. ^ http://www.cie.iarc.fr/htdocs/monographs/vol32/anthracene.html

External links[edit]