Coronene
Encyclopedia
Coronene is a polycyclic aromatic hydrocarbon
(PAH) comprising six peri-fused benzene
rings. Its chemical formula is . It is a yellow material that dissolves in such solvents as benzene
, toluene
, and dichloromethane
. Its solutions emit blue light fluorescence
under UV light. Its emission spectrum is not symmetrical with its excitation spectrum and varies in the number of bands and their relative intensities depending on the solvent. It has been used as a solvent probe, similar to pyrene
.
It occurs naturally as the mineral
carpathite
, which is characterized by flakes of pure coronene embedded in sedimentary rock. This mineral may result from ancient hydrothermal vent activity.
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). Coronene has been seen on the surface of Titan
(Saturn's moon). It can cause DNA damage in mammals.
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.
According to in silico
calculations on the following hypothetical isodesmic reactions, coronene has a somewhat higher resonance energy per pi electron (REPE) than benzene
:
On the other hand the perimeter C–C bond length
alternations are larger than in benzene.
. They are known to self-assemble
into a columnar phase
. One derivative in particular forms carbon nanotubes with interesting electrical properties. The columnar phase in this compound further organises itself into sheets, which ultimately roll up like a carpet to form multi-walled nanotubes with an outer diameter of 20 nanometers and a wall thickness of 3 nanometers. In this geometry, the stacks of coronene disks are aligned with the length of the tube. The nanotubes have sufficient length to fit between two platinum
nanogap electrodes produced by scanning probe
nanofabrication and are 180 nanometer apart. The nanotubes as such are insulating, but, after one-electron oxidation with nitrosonium tetrafluoroborate
, they conduct electricity.
Organic synthesis
of a hexa-benzopericoronene starts with an Aldol condensation
reaction of an acetone
derivative with a benzil
derivative to substituted cyclopentadienone. This compound is reacted with an alkyne
in a Diels-Alder reaction
and subsequent expulsion of carbon monoxide
to the hexaphenylbenzene
, which is oxidized by Iron(III) chloride
in nitromethane
.
Polycyclic aromatic hydrocarbon
Polycyclic aromatic hydrocarbons , also known as poly-aromatic hydrocarbons or polynuclear aromatic hydrocarbons, are potent atmospheric pollutants that consist of fused aromatic rings and do not contain heteroatoms or carry substituents. Naphthalene is the simplest example of a PAH...
(PAH) comprising six peri-fused benzene
Benzene
Benzene is an organic chemical compound. It is composed of 6 carbon atoms in a ring, with 1 hydrogen atom attached to each carbon atom, with the molecular formula C6H6....
rings. Its chemical formula is . It is a yellow material that dissolves in such solvents as benzene
Benzene
Benzene is an organic chemical compound. It is composed of 6 carbon atoms in a ring, with 1 hydrogen atom attached to each carbon atom, with the molecular formula C6H6....
, toluene
Toluene
Toluene, formerly known as toluol, is a clear, water-insoluble liquid with the typical smell of paint thinners. It is a mono-substituted benzene derivative, i.e., one in which a single hydrogen atom from the benzene molecule has been replaced by a univalent group, in this case CH3.It is an aromatic...
, and dichloromethane
Dichloromethane
Dichloromethane is an organic compound with the formula CH2Cl2. This colorless, volatile liquid with a moderately sweet aroma is widely used as a solvent. Although it is not miscible with water, it is miscible with many organic solvents...
. Its solutions emit blue light fluorescence
Fluorescence
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation of a different wavelength. It is a form of luminescence. In most cases, emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation...
under UV light. Its emission spectrum is not symmetrical with its excitation spectrum and varies in the number of bands and their relative intensities depending on the solvent. It has been used as a solvent probe, similar to pyrene
Pyrene
Pyrene is a polycyclic aromatic hydrocarbon consisting of four fused benzene rings, resulting in a flat aromatic system. The chemical formula is . This colourless solid is the smallest peri-fused PAH...
.
It occurs naturally as the mineral
Mineral
A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...
carpathite
Carpathite
Carpathite is a rare hydrocarbon mineral. It is the mineral form of the polycyclic aromatic hydrocarbon coronene with formula: C24H12....
, which is characterized by flakes of pure coronene embedded in sedimentary rock. This mineral may result from ancient hydrothermal vent activity.
Coronene is produced in the petroleum refining process of hydrocracking, where it can dimerize to a fifteen ring PAH, trivially named "dicoronylene
Dicoronylene
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...
" (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). Coronene has been seen on the surface of Titan
Titan (moon)
Titan , or Saturn VI, is the largest moon of Saturn, the only natural satellite known to have a dense atmosphere, and the only object other than Earth for which clear evidence of stable bodies of surface liquid has been found....
(Saturn's moon). It can cause DNA damage in mammals.
The compound is of theoretical interest to organic chemists because of its aromaticity
Aromaticity
In organic chemistry, Aromaticity is a chemical property in which a conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibit a stabilization stronger than would be expected by the stabilization of conjugation alone. The earliest use of the term was in an article by August...
. 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.
According to in silico
In silico
In silico is an expression used to mean "performed on computer or via computer simulation." The phrase was coined in 1989 as an analogy to the Latin phrases in vivo and in vitro which are commonly used in biology and refer to experiments done in living organisms and outside of living organisms,...
calculations on the following hypothetical isodesmic reactions, coronene has a somewhat higher resonance energy per pi electron (REPE) than benzene
Benzene
Benzene is an organic chemical compound. It is composed of 6 carbon atoms in a ring, with 1 hydrogen atom attached to each carbon atom, with the molecular formula C6H6....
:
- coronene + 24 * ethyleneEthyleneEthylene is a gaseous organic compound with the formula . It is the simplest alkene . Because it contains a carbon-carbon double bond, ethylene is classified as an unsaturated hydrocarbon. Ethylene is widely used in industry and is also a plant hormone...
→ 18 * butadiene REPE 4.2 kcal/molMole (unit)The mole is a unit of measurement used in chemistry to express amounts of a chemical substance, defined as an amount of a substance that contains as many elementary entities as there are atoms in 12 grams of pure carbon-12 , the isotope of carbon with atomic weight 12. This corresponds to a value...
(17.6 kJ/mol) - benzene + 3 * ethylene → 3 * butadiene REPE 3.6 kcal/mol (15 kJ/mol)
On the other hand the perimeter C–C bond length
Bond length
- Explanation :Bond length is related to bond order, when more electrons participate in bond formation the bond will get shorter. Bond length is also inversely related to bond strength and the bond dissociation energy, as a stronger bond will be shorter...
alternations are larger than in benzene.
Hexa-benzopericoronenes
Hexa-benzopericoronenes are members of the coronene family and investigated in supramolecular electronicsSupramolecular electronics
Supramolecular electronics is the experimental field of supramolecular chemistry that bridges the gap between molecular electronics and bulk plastics in the construction of electronic circuitry at the nanoscale 1...
. They are known to self-assemble
Molecular self-assembly
Molecular self-assembly is the process by which molecules adopt a defined arrangement without guidance or management from an outside source. There are two types of self-assembly, intramolecular self-assembly and intermolecular self-assembly...
into a columnar phase
Columnar phase
The columnar phase is a class of mesophases in which molecules assemble into cylindrical structures to act as mesogens. Originally, these kinds of liquid crystals were called discotic liquid crystals because the columnar structures are composed of flat-shaped discotic molecules stacked...
. One derivative in particular forms carbon nanotubes with interesting electrical properties. The columnar phase in this compound further organises itself into sheets, which ultimately roll up like a carpet to form multi-walled nanotubes with an outer diameter of 20 nanometers and a wall thickness of 3 nanometers. In this geometry, the stacks of coronene disks are aligned with the length of the tube. The nanotubes have sufficient length to fit between two platinum
Platinum
Platinum is a chemical element with the chemical symbol Pt and an atomic number of 78. Its name is derived from the Spanish term platina del Pinto, which is literally translated into "little silver of the Pinto River." It is a dense, malleable, ductile, precious, gray-white transition metal...
nanogap electrodes produced by scanning probe
Scanning probe microscopy
Scanning Probe Microscopy is a branch of microscopy that forms images of surfaces using a physical probe that scans the specimen. An image of the surface is obtained by mechanically moving the probe in a raster scan of the specimen, line by line, and recording the probe-surface interaction as a...
nanofabrication and are 180 nanometer apart. The nanotubes as such are insulating, but, after one-electron oxidation with nitrosonium tetrafluoroborate
Nitrosonium tetrafluoroborate
Nitrosonium tetrafluoroborate, also called nitrosyl tetrafluoroborate, is a chemical compound with the chemical formula NOBF4. This colourless solid finds use in organic synthesis as a nitrosating agent....
, they conduct electricity.
Organic synthesis
Organic synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has...
of a hexa-benzopericoronene starts with an Aldol condensation
Aldol condensation
An aldol condensation is an organic reaction in which an enol or an enolate ion reacts with a carbonyl compound to form a β-hydroxyaldehyde or β-hydroxyketone, followed by a dehydration to give a conjugated enone....
reaction of an acetone
Acetone
Acetone is the organic compound with the formula 2CO, a colorless, mobile, flammable liquid, the simplest example of the ketones.Acetone is miscible with water and serves as an important solvent in its own right, typically as the solvent of choice for cleaning purposes in the laboratory...
derivative with a benzil
Benzil
Benzil is the organic compound with the formula 2, generally abbreviated 2. This yellow solid is one of the most common diketones...
derivative to substituted cyclopentadienone. This compound is reacted with an alkyne
Alkyne
Alkynes are hydrocarbons that have a triple bond between two carbon atoms, with the formula CnH2n-2. Alkynes are traditionally known as acetylenes, although the name acetylene also refers specifically to C2H2, known formally as ethyne using IUPAC nomenclature...
in a Diels-Alder reaction
Diels-Alder reaction
The Diels–Alder reaction is an organic chemical reaction between a conjugated diene and a substituted alkene, commonly termed the dienophile, to form a substituted cyclohexene system. The reaction can proceed even if some of the atoms in the newly formed ring are not carbon...
and subsequent expulsion of carbon monoxide
Carbon monoxide
Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...
to the hexaphenylbenzene
Hexaphenylbenzene
Hexaphenylbenzene is an aromatic compound composed of a benzene ring substituted with six phenyl rings.It may be prepared through a Diels-Alder reaction by refluxing tetraphenylcyclopentadienone and diphenylacetylene in benzophenone or other high-temperature solvent.-Structure:Due to steric...
, which is oxidized by Iron(III) chloride
Iron(III) chloride
Iron chloride, also called ferric chloride, is an industrial scale commodity chemical compound, with the formula FeCl3. The colour of iron chloride crystals depends on the viewing angle: by reflected light the crystals appear dark green, but by transmitted light they appear purple-red...
in nitromethane
Nitromethane
Nitromethane is an organic compound with the chemical formula . It is the simplest organic nitro compound. It is a slightly viscous, highly polar liquid commonly used as a solvent in a variety of industrial applications such as in extractions, as a reaction medium, and as a cleaning solvent...
.
See also
- A related compound lacking the central core: cyclooctadecanonaeneCyclooctadecanonaeneCyclooctadecanonaene or [18]annulene is an annulene with chemical formula . This hydrocarbon obeys Hückel's rule and is, therefore, an aromatic compound...
- Coronene's dimer: DicoronyleneDicoronyleneDicoronylene 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...