Names | |
---|---|
Preferred IUPAC name Coronene [1] | |
Other names [6]circulene X1001757-9, superbenzene, cyclobenzene | |
Identifiers | |
3D model (JSmol) | |
658468 | |
ChEBI | |
ChemSpider | |
ECHA InfoCard | 100.005.348 |
EC Number |
|
286459 | |
KEGG | |
PubChem CID | |
UNII | |
CompTox Dashboard (EPA) | |
| |
| |
Properties | |
C24H12 | |
Molar mass | 300.360 g·mol−1 |
Appearance | Yellow powder [2] |
Density | 1.371 g/cm3 [3] |
Melting point | 437.3 °C (819.1 °F; 710.5 K) [3] |
Boiling point | 525 °C (977 °F; 798 K) [3] |
0.14 μg/L [4] | |
Solubility | Very soluble: benzene, toluene, hexane, [5] Chloroform (1 mmol·L−1) [6] and ethers, sparingly soluble in ethanol. |
-243.3·10−6 cm3/mol | |
Structure | |
Monoclinic | |
P21/n [7] | |
D6h | |
a = 10.02 Å, b = 4.67 Å, c = 15.60 Å α = 90°, β = 106.7°, γ = 90° | |
Formula units (Z) | 2 |
0 D | |
Hazards | |
GHS labelling: | |
Warning | |
H371 | |
P260, P264, P270, P309+P311, P405, P501 | |
NFPA 704 (fire diamond) | |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). |
Coronene (also known as superbenzene and cyclobenzene) is a polycyclic aromatic hydrocarbon (PAH) comprising seven peri-fused benzene rings. [8] Its chemical formula is C
24H
12. It is a yellow material that dissolves in common solvents including benzene, toluene, and dichloromethane. Its solutions emit blue light fluorescence under UV light. It has been used as a solvent probe, similar to pyrene.
The compound is of theoretical interest to organic chemists because of its aromaticity. It can be described by 20 resonance structures or by a set of three mobile Clar sextets. In the Clar sextet case, the most stable structure for coronene has only the three isolated outer sextets as fully aromatic although superaromaticity would still be possible when these sextets are able to migrate into the next ring.
Coronene occurs naturally as the very rare mineral carpathite, which is characterized by flakes of pure coronene embedded in sedimentary rock. This mineral may be created from ancient hydrothermal vent activity. [9] In earlier times this mineral was also called karpatite or pendletonite. [10]
The presence of coronene putatively formed from contact of magma with fossil fuel deposits has been used to argue that the Permian-Triassic “Great Dying” event was caused by a greenhouse gas warming episode triggered by large-scale Siberian vulcanism. [11]
Coronene is produced in the petroleum-refining process of hydrocracking, where it can dimerize to a fifteen ring PAH, trivially named "dicoronylene" (formally named benzo[10,11]phenanthro[2',3',4',5',6':4,5,6,7]chryseno[1,2,3-bc]coronene or benzo[1,2,3-bc:4,5,6-b'c']dicoronene). Centimeter-long crystals can be grown from a supersaturated solution of the molecules in toluene (ca. 2.5 mg/ml), which is slowly cooled (ca. 0.04 K/min) from 328 K to 298 K over a period of 12 hours. [7]
Coronene is a planar circulene. It forms needle-like crystals with a monoclinic, herringbone-like structure. The most common polymorph is γ, but β form can also be produced in an applied magnetic field (ca. 1 Tesla) [7] or by phase transition from γ decreasing the temperature below 158 K. [12] The structure containing two C-H groups on one benzene ring, so-called DUO, was analyzed by infrared spectroscopy. [13]
Coronene has been used in the synthesis of graphene. For example, coronene molecules evaporated onto a copper surface at 1000 degrees Celsius will form a graphene lattice which can then be transferred onto another substrate. [14]
Aromatic compounds, also known as "mono- and polycyclic aromatic hydrocarbons", are organic compounds containing one or more aromatic rings. The word "aromatic" originates from the past grouping of molecules based on smell, before their general chemical properties were understood. The current definition of aromatic compounds does not have any relation with their smell.
In chemistry, aromaticity means the molecule has cyclic (ring-shaped) structures with pi bonds in resonance. Aromatic rings give increased stability compared to saturated compounds having single bonds, and other geometric or connective non-cyclic arrangements with the same set of atoms. Aromatic rings are very stable and do not break apart easily. Organic compounds that are not aromatic are classified as aliphatic compounds—they might be cyclic, but only aromatic rings have enhanced stability. The term aromaticity with this meaning is historically related to the concept of having an aroma, but is a distinct property from that meaning.
A polycyclic aromatic hydrocarbon (PAH) is a class of organic compounds that is composed of multiple aromatic rings. The simplest representative is naphthalene, having two aromatic rings and the three-ring compounds anthracene and phenanthrene. PAHs are uncharged, non-polar and planar. Many are colorless. Many of them are found in coal and in oil deposits, and are also produced by the incomplete combustion of organic matter—for example, in engines and incinerators or when biomass burns in forest fires.
Triphenylene is an organic compound with the formula (C6H4)3. A flat polycyclic aromatic hydrocarbon (PAH), it consists of four fused benzene rings. Triphenylene has delocalized 18-π-electron systems based on a planar structure, corresponding to the symmetry group D3h. It is a white or colorless solid.
Hexacene is an aromatic compound consisting of six linearly-fused benzene rings. It is a blue-green, air-stable solid with low solubility.
Ovalene is a polycyclic aromatic hydrocarbon with the formula C32H14, which consists of ten peri-fused six-membered rings. It is very similar to coronene.
Carpathite is a very rare hydrocarbon mineral, consisting of exceptionally pure coronene (C24H12), a polycyclic aromatic hydrocarbon. The name has been spelled karpatite and the mineral was improperly renamed pendletonite.
Chrysene is a polycyclic aromatic hydrocarbon (PAH) with the molecular formula C
18H
12 that consists of four fused benzene rings. It is a natural constituent of coal tar, from which it was first isolated and characterized. It is also found in creosote at levels of 0.5–6 mg/kg.
In organic and physical organic chemistry, Clar's rule is an empirical rule that relates the chemical stability of a molecule with its aromaticity. It was introduced in 1972 by the Austrian organic chemist Erich Clar in his book The Aromatic Sextet. The rule states that given a polycyclic aromatic hydrocarbon, the resonance structure most important to characterize its properties is that with the largest number of aromatic π-sextets i.e. benzene-like moieties.
Dicoronylene is the trivial name for a very large polycyclic aromatic hydrocarbon. Its formal name is benzo[10,11]phenanthro[2',3',4',5',6':4,5,6,7]chryseno[1,2,3-bc]coronene or benzo[1,2,3-bc:4,5,6-b'c']dicoronene. It has 15 rings and is a brick-red solid. Its formula is C
48H
20. Dicoronylene sublimes under high vacuum, 0.001 torr, between 250 °C and 300 °C.
Benzo[c]phenanthrene is a polycyclic aromatic hydrocarbon with the chemical formula C18H12. It is a white solid that is soluble in nonpolar organic solvents. It is a nonplanar molecule consisting of the fusion of four fused benzene rings. The compound is of mainly theoretical interest but it is environmentally occurring and weakly carcinogenic.
Kekulene is a polycyclic aromatic hydrocarbon which consists of 12 fused benzene rings arranged in a circle. It is therefore classified as a [12]-circulene with the chemical formula C48H24. It was first synthesized in 1978, and was named in honor of August Kekulé, the discoverer of the structure of the benzene molecule.
Olympicene is an organic carbon-based molecule formed of five rings, of which four are benzene rings, joined in the shape of the Olympic rings.
Hexa-peri-hexabenzocoronene (HBC) is a polycyclic aromatic hydrocarbon with the molecular formula C42H18. It consists of a central coronene molecule, with an additional benzene ring fused between each adjacent pair of rings around the periphery. It is sometimes simply called hexabenzocoronene, however, there are other chemicals that share this less-specific name, such as hexa-cata-hexabenzocoronene.
Benz[e]acephenanthrylene is an organic compound with the chemical formula C20H12. It is a polycyclic aromatic hydrocarbon (PAH) made of four benzene rings around a 5-membered ring.
Benzo[c]fluorene is a polycyclic aromatic hydrocarbon (PAH) with mutagenic activity. It is a component of coal tar, cigarette smoke and smog and thought to be a major contributor to its carcinogenic properties. The mutagenicity of benzo[c]fluorene is mainly attributed to formation of metabolites that are reactive and capable of forming DNA adducts. According to the KEGG it is a group 3 carcinogen. Other names for benzo[c]fluorene are 7H-benzo[c]fluorene, 3,4-benzofluorene, and NSC 89264.
Hexa-cata-hexabenzocoronene (hexabenzo[a,d,g,j,m,p]coronene) is a polycyclic aromatic hydrocarbon with the molecular formula C48H24. It consists of a central coronene molecule, with an additional benzene ring fused onto each ring around the periphery.
Superphenalene is a very large polycyclic aromatic hydrocarbon (PAH) with chemical formula C96H30. It can be formally considered to consist of three fused superbenzenes (hexa-peri-hexabenzocoronene).
Indeno[1,2,3-cd]pyrene is a polycyclic aromatic hydrocarbon (PAH), one of 16 PAHs generally measured in studies of environmental exposure and air pollution. Many compounds of this class are formed when burning coal, oil, gas, wood, household waste and tobacco, and can bind to or form small particles in the air. The compounds are known to have toxic, mutagenic and/or carcinogenic properties. Over 100 different PAHs have been identified in environmental samples. One of these 16 is Indeno[1,2,3-cd]pyrene (IP). IP is the combination of an indeno molecule and a pyrene molecule with a fluoranthene network. In 1962, the National Cancer Institute reported that indeno[1,2,3-cd]pyrene has a slight tumor activity. This was confirmed in 1973 by the IARC in mice testing.
Borepins are a class of boron-containing heterocycles used in main group chemistry. They consist of a seven-membered unsaturated ring with a tricoordinate boron in it. Simple borepins are analogues of cycloheptatriene, which is a seven-membered ring containing three carbon-carbon double bonds, each of which contributes 2π electrons for a total of 6π electrons. Unlike other seven-membered systems such as silepins and phosphepins, boron has a vacant p-orbital that can interact with the π and π* orbitals of the cycloheptatriene. This leads to an isoelectronic state akin to that of the tropylium cation, aromatizing the borepin while also allowing it to act as a Lewis acid. The aromaticity of borepin is relatively weak compared to traditional aromatics such as benzene or even cycloheptatriene, which has led to the synthesis of many fused, π-conjugated borepin systems over the years. Simple and complex borepins have been extensively studied more recently due to their high fluorescence and potential applications in technologies like organic light-emitting diodes (OLEDs) and photovoltaic cells.