Anthracene

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.[13]

Anthracene
Names
Preferred IUPAC name
Anthracene
Systematic IUPAC name
Tricyclo[8.4.0.03,8]tetradeca-1,3,5,7,9,11,13-heptaene
Identifiers
3D model (JSmol)
Beilstein Reference
 1905429
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.003.974
EC Number
  • 217-004-5
Gmelin Reference
 67837
KEGG
RTECS number
  • CA9350000
UNII
CompTox Dashboard (EPA)
Properties
C14H10
Molar mass 178.234 g·mol−1
Appearance Colorless
Odor Weak aromatic
Density 1.28 g/cm3 (25 °C)[1]
0.969 g/cm3 (220 °C)
Melting point 216 °C (421 °F; 489 K)[1] at 760 mmHg
Boiling point 341.3 °C (646.3 °F; 614.5 K)[1] at 760 mmHg
0.022 mg/L (0 °C)
0.044 mg/L (25 °C)
0.29 mg/L (50 °C)
0.00045% w/w (100 °C, 3.9 MPa)[2]
Solubility Soluble in alcohol, (C2H5)2O, acetone, C6H6, CHCl3,[1] CS2[3]
Solubility in ethanol 0.76 g/kg (16 °C)
1.9 g/kg (19.5 °C)
3.28 g/kg (25 °C)[3]
Solubility in methanol 18 g/kg (19.5 °C)[3]
Solubility in hexane 3.7 g/kg[3]
Solubility in toluene 9.2 g/kg (16.5 °C)
129.4 g/kg (100 °C)[3]
Solubility in carbon tetrachloride 7.32 g/kg[3]
log P 4.56
Vapor pressure 0.01 kPa (125.9 °C)
0.1 kPa (151.5 °C)[4]
13.4 kPa (250 °C)[5]
0.0396 L·atm/mol[6]
UV-vis (λmax) 345.6 nm, 363.2 nm[5]
−129.8×10−6 cm3/mol[7]
Thermal conductivity 0.1416 W/(m·K) (240 °C)
0.1334 W/(m·K) (270 °C)
0.1259 W/(m·K) (300 °C)[8]
Viscosity 0.602 cP (240 °C)
0.498 cP (270 °C)
0.429 cP (300 °C)[8]
Structure
Monoclinic (290 K)[9]
Space group
 P21/b[9]
D5
2h[9]
Lattice constant
a = 8.562 Å, b = 6.038 Å, c = 11.184 Å[9]
α = 90°, β = 124.7°, γ = 90°
Thermochemistry[10]
210.5 J/(mol·K)
Std molar
entropy (So298)
 207.5 J/(mol·K)
129.2 kJ/mol
Std enthalpy of
combustion (ΔcH⦵298)
 7061 kJ/mol[5]
Hazards
GHS pictograms [11]
GHS Signal word Warning
GHS hazard statements
 H315, H319, H335, H410[11]
GHS precautionary statements
 P261, P273, P305+351+338, P501[11]
NFPA 704 (fire diamond)
1
2
1
Flash point 121 °C (250 °F; 394 K)[11]
Autoignition
temperature
 540 °C (1,004 °F; 813 K)[11]
Lethal dose or concentration (LD, LC):
4900 mg/kg (rats, oral)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Occurrence and production

Coal tar, which contains around 1.5% anthracene, remains a major source of this material. Common impurities are phenanthrene and carbazole. The mineral form of anthracene is called freitalite and is related to a coal deposit.[14] 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

Reduction

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.

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+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.[15][16]

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

Diels alder reaction of anthracene with singlet oxygen

With electrophiles

Chemical oxidation occurs readily, giving anthraquinone, C14H8O2 (below), for example using hydrogen peroxide and vanadyl acetylacetonate.[17]

Anthraquione

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.[18]

Uses

Anthracene is converted mainly to anthraquinone, a precursor to dyes.[19]

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.[20] Anthracene also used in manufacturing of anthraquinone.

Derivatives
False-color AFM image of anthracene diradical, where hydrogen atoms are removed at carbons 9 and 10

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)[21][22] 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.

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.[19]

See also
  • 9,10-Dithioanthracene, derivative with two thiol groups added to the central ring
  • Phenanthrene
  • Tetracene

References
  1. Haynes, p. 3.28
  2. Haynes, p. 5.157
  3. Seidell, Atherton; Linke, William F. (1919). Solubilities of Inorganic and Organic Compounds (2nd ed.). New York: D. Van Nostrand Company. pp. 81.
  4. Haynes, p. 6.116
  5. Anthracene in Linstrom, Peter J.; Mallard, William G. (eds.); NIST Chemistry WebBook, NIST Standard Reference Database Number 69, National Institute of Standards and Technology, Gaithersburg (MD), http://webbook.nist.gov (retrieved 2014-06-22)
  6. Haynes, p. 5.157
  7. Haynes, p. 3.579
  8. "Properties of Anthracene". www.infotherm.com. Wiley Information Services GmbH. Archived from the original on 2014-11-01. Retrieved 2014-06-22.
  9. Douglas, Bodie E.; Ho, Shih-Ming (2007). Structure and Chemistry of Crystalline Solids. New York: Springer Science+Business Media, Inc. p. 289. ISBN 978-0-387-26147-8.
  10. Haynes, p. 5.41
  11. Sigma-Aldrich Co., Anthracene. Retrieved on 2014-06-22.
  12. "MSDS of Anthracene". www.fishersci.ca. Fisher Scientific. Retrieved 2014-06-22.
  13. Lindsey, Jonathan; et al. "Anthracene". PhotochemCAD. Retrieved 20 February 2014.
  14. Freitalite, Mindat, https://www.mindat.org/min-54360.html
  15. Rickborn, Bruce (1998). "The Retro-Diels-Alder Reaction Part I. C−C Dienophiles". Organic Reactions. pp. 1–393. doi:10.1002/0471264180.or052.01. ISBN 978-0471264187.
  16. Bouas-Laurent, Henri; Desvergne, Jean-Pierre; Castellan, Alain; Lapouyade, Rene (2000). "Photodimerization of anthracenes in fluid solution: Structural aspects". Chemical Society Reviews. 29: 43–55. doi:10.1039/a801821i.
  17. Charleton, Kimberly D. M.; Prokopchuk, Ernest M. (2011). "Coordination Complexes as Catalysts: The Oxidation of Anthracene by Hydrogen Peroxide in the Presence of VO(acac)2". Journal of Chemical Education. 88 (8): 1155–1157. Bibcode:2011JChEd..88.1155C. doi:10.1021/ed100843a.
  18. Škalamera, Đani; Veljković, Jelena; Ptiček, Lucija; Sambol, Matija; Mlinarić-Majerski, Kata; Basarić, Nikola (2017). "Synthesis of asymmetrically disubstituted anthracenes". Tetrahedron. 73 (40): 5892–5899. doi:10.1016/j.tet.2017.08.038.
  19. Collin, Gerd; Höke, Hartmut and Talbiersky, Jörg (2006) "Anthracene" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim. doi:10.1002/14356007.a02_343.pub2
  20. Zeitler, Alex (2012-06-27) Conformal Coating 101: General Overview, Process Development, and Control Methods. BTW, Inc.
  21. 1-Hydroxyanthracene. NIST datapage
  22. 2-Hydroxyanthracene. NIST datapage

Cited sources
  • Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). CRC Press. ISBN 1439855110.
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