Anthracene
Names IUPAC name Identifiers 1905429 ChEBI ChEMBL ChemSpider DrugBank ECHA InfoCard 100.003.974 EC Number 67837 KEGG RTECS number UNII 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) 19 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] P21/b[9] D52h[9] Thermochemistry[10] 210.5 J/(mol·K) 207.5 J/(mol·K) 129.2 kJ/mol 7061 kJ/mol[5] Hazards GHS labelling: [11] Warning H302, H305, H315, H319, H335, H410[11] P261, P273, P305+P351+P338, P501[11] NFPA 704 (fire diamond) Flash point 121 °C (250 °F; 394 K)[11] 540 °C (1,004 °F; 813 K)[11] Lethal dose or concentration (LD, LC): 100-149 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, as a scintillator to detect high energy particles, as production of pharmaceutical drugs. Anthracene is colorless but exhibits a blue (400-500 nm peak) fluorescence under ultraviolet radiation.[13]
Crude anthracene (with a melting point of only 180°) was discovered in 1832 by Jean-Baptiste Dumas and Auguste Laurent[14] who crystalized it from a fraction of coal tar later known as “anthracene oil”. Since their (inaccurate) measurements showed the proportions of carbon and hydrogen of it to be the same as in naphthalene, Laurent called it paranaphtaline in his 1835 publication of the discovery,[15] which is translated to English as paranaphthalene.[14] Two years later, however, he decided to rename the compound to its modern name derived from Ancient Greek: ἄνθραξ, romanized: anthrax, lit. ’coal’ because after discovering other polyaromatic hydrocarbons he decided it was only one of isomers of naphthalene.[16] This notion was disproved in 1850s and 1860s.[17][18]
Anthracene, as many other polycyclic aromatic hydrocarbons, is generated during combustion processes. Most human exposure is through tobacco smoke or ingestion of charred food.
The mineral form of anthracene is called freitalite and is related to a coal deposit.[19] Coal tar, which contains around 1.5% anthracene, remains a major industrial 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, for example from o-tolyl phenyl ketone.[20]
Reduction of anthracene with alkali metals yields the deeply colored radical anion salts M+[anthracene]− (M = Li, Na, K). Reduction with sodium in ethanol gives 9,10-dihydroanthracene, preserving the aromaticity of the two flanking rings.[21]
In any solvent except water,[22] 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.[23][24]
Anthracene also reacts with dienophile singlet oxygen in a [4+2]-cycloaddition (Diels-Alder reaction):
Chemical oxidation occurs readily, giving anthraquinone, C14H8O2 (below), for example using hydrogen peroxide and vanadyl acetylacetonate.[25]
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.[26] Bromination of anthracene gives 9,10-dibromoanthracene.[27]
Anthracene proper has application as an organic semiconductor and chemical feedstock for various preservatives and dyes.
Anthracene is a wide band-gap organic semiconductor, with an emission spectrum peaking between 400 nm and 440 nm. Organic field-effect transistors have been constructed from it. In particle physics, it is used as a scintillator to detect high-energy photons, electrons, or alpha particles.[28] Plastics, such as polyvinyltoluene, can be doped with anthracene to produce an approximately water-equivalent scintillator in radiation therapy dosimetry.
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.[29]
It is also used in wood preservatives, insecticides, and coating materials.[citation needed]
A variety of anthracene derivatives find specialized uses. Industrially, anthracene is converted mainly to anthraquinone, a precursor to dyes.[30] Derivatives having a hydroxyl group are 1-hydroxyanthracene and 2-hydroxyanthracene, homologous to phenol and naphthols, and hydroxyanthracene (also called anthrol, and anthracenol)[31][32] are pharmacologically active. Anthracene may also be found with multiple hydroxyl groups, as in 9,10-dihydroxyanthracene.
Some anthracene derivatives are used as pharmaceutical drugs, including bisantrene, trazitiline, and benzoctamine.
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.[30] Nevertheless, the International Agency for Research on Cancer (IARC) classifies anthracene as IARC group 2B, possibly carcinogenic to humans.[33]
Anthracene is readily biodegraded in soil. It is especially susceptible to degradation in the presence of light.[30]
- 9,10-Dithioanthracene, derivative with two thiol groups added to the central ring
- Phenanthrene
- Acridine
- Phenazine
- Tetracene
- Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). CRC Press. ISBN 978-1-4398-5511-9.
- International Chemical Safety Card 0825
- IARC – Monograph 32
- National Pollutant Inventory – Polycyclic Aromatic Hydrocarbon Fact Sheet
- European Chemicals Agency – ECHA
- “Anthracene” . Encyclopædia Britannica (11th ed.). 1911.
