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, 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]

Anthracene

Skeletal formula and numbering system of anthracene
Anthracene
Names
IUPAC name Anthracene
Identifiers
CAS Number	120-12-7 Y
3D model (JSmol)	Interactive image
Beilstein Reference	1905429
ChEBI	CHEBI:35298 Y
ChEMBL	ChEMBL333179 Y
ChemSpider	8111 Y
DrugBank	DB07372 Y
ECHA InfoCard	100.003.974
EC Number	217-004-5
Gmelin Reference	67837
KEGG	C14315 Y
PubChem CID	8418
RTECS number	CA9350000
UNII	EH46A1TLD7 Y
CompTox Dashboard (EPA)	DTXSID0023878
InChI InChI=1S/C14H10/c1-2-6-12-10-14-8-4-3-7-13(14)9-11(12)5-1/h1-10H Y Key: MWPLVEDNUUSJAV-UHFFFAOYSA-N Y InChI=1/C14H10/c1-2-6-12-10-14-8-4-3-7-13(14)9-11(12)5-1/h1-10H Key: MWPLVEDNUUSJAV-UHFFFAOYAK
SMILES c1ccc2cc3ccccc3cc2c1
Properties
Chemical formula	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
Solubility in water	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]
Henry's law constant (kH)	0.0396 L·atm/mol[6]
UV-vis (λmax)	345.6 nm, 363.2 nm[5]
Magnetic susceptibility (χ)	−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
Crystal structure	Monoclinic (290 K)[9]
Space group	P21/b[9]
Point group	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]
Heat capacity (C)	210.5 J/(mol·K)
Std molar entropy (S⦵298)	207.5 J/(mol·K)
Std enthalpy of formation (ΔfH⦵298)	129.2 kJ/mol
Std enthalpy of combustion (ΔcH⦵298)	7061 kJ/mol[5]
Hazards
GHS labelling:
Pictograms	[11]
Signal word	Warning
Hazard statements	H302, H305, H315, H319, H335, H410[11]
Precautionary statements	P261, P273, P305+P351+P338, P501[11]
NFPA 704 (fire diamond)	[12] 1 1 0
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):
LD50 (median dose)	100-149 mg/kg (rats, oral)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

History and etymology

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]

Occurrence and production

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]

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.^[21]

Cycloadditions

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):

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.^[25]

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.^[26] Bromination of anthracene gives 9,10-dibromoanthracene.^[27]

Uses

Anthracene proper has application as an organic semiconductor and chemical feedstock for various preservatives and dyes.

Electronics

Fluorescence of anthracene under UV light

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]}

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. 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.

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.^[30] The International Agency for Research on Cancer (IARC) classifies anthracene as IARC group 2B, possibly carcinogenic to humans.^[33]

See also

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