Dicoronylene
Encyclopedia
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 (IUPAC name) or benzo[1,2,3-bc:4,5,6-b'c']dicoronene (name sometimes used in Chemical Abstracts). It has 15 rings and is a brick-red solid. Its formula is . Dicoronylene sublimes under high vacuum, 0.001 torr
, between 250 °C and 300 °C.
with maleic anhydride
on one or both of the central bay regions on either side of the bridging ring. The double-bond of maleic anhydride forms two carbon-carbon bonds on the ends of the bay region, making a new six-membered ring. Heating removes the anhydride as carbon dioxide
gas and gives the corresponding 16-ring and 17-ring PAHs.
. This residue contained large amounts of coronene
and ovalene
. After these were extracted and identified, a reddish residue remained, which was sparingly soluble in organic solvents. Elemental analysis indicated that it was most likely the condensed dimer of coronene
.
Dicoronylene was later discovered to occur as a by-product of the catalytic hydrocracking used in petroleum processing. It is formed when two coronene
molecules fuse. It is estimated that catalytical hydrocracking produces several hundred metric tons of dicoronylene worldwide per year, making it the most prevalent large PAH. In this process, the analogous 18-ring PAH formed from coronene and ovalene is also formed in 1% to 20% proportions. It is purple in color.
formed on hydrocracking catalysts, which reduces their activity.
Thermal pyrolysis
of coronene
shows masses of dicoronylene and the condensed trimer, tetramer, and pentamer in the mass spectrum
of the black product. These larger coronene condensates are black in color.
Dicoronylene is moderately soluble in 1,2,4-trichlorobenzene
and these solutions have a greenish yellow fluorescence
. Unlike coronene, dicoronylene has symmetrical fluorescence excitation and emission spectra. It is virtually insoluble in most solvents.
Dicoronylene has been studied as a model for interstellar PAHs. Its large size and planarity have also shown promise as a chromatographic separation material.
Trivial name
In chemistry, a trivial name is a common name or vernacular name; it is a non-systematic name or non-scientific name. That is, the name is not recognised according to the rules of any formal system of nomenclature...
for a very large polycyclic aromatic hydrocarbon
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...
. Its formal name is benzo[10,11]phenanthro[2',3',4',5',6':4,5,6,7]chryseno[1,2,3-bc]coronene (IUPAC name) or benzo[1,2,3-bc:4,5,6-b'c']dicoronene (name sometimes used in Chemical Abstracts). It has 15 rings and is a brick-red solid. Its formula is . Dicoronylene sublimes under high vacuum, 0.001 torr
Torr
The torr is a non-SI unit of pressure with the ratio of 760 to 1 standard atmosphere, chosen to be roughly equal to the fluid pressure exerted by a millimetre of mercury, i.e., a pressure of 1 torr is approximately equal to 1 mmHg...
, between 250 °C and 300 °C.
Structure
Due to its large size and limited availability, the organic chemistry of dicoronylene is little known. Dicoronylene does undergo a Diels-Alder reactionDiels-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...
with maleic anhydride
Maleic anhydride
Maleic anhydride is an organic compound with the formula C2H22O. It is the acid anhydride of maleic acid and in its pure state it is a colourless or white solid with an acrid odour....
on one or both of the central bay regions on either side of the bridging ring. The double-bond of maleic anhydride forms two carbon-carbon bonds on the ends of the bay region, making a new six-membered ring. Heating removes the anhydride as carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
gas and gives the corresponding 16-ring and 17-ring PAHs.
Occurrence
Dicoronylene was first observed in the solid residue produced in coal gasificationGasification
Gasification is a process that converts organic or fossil based carbonaceous materials into carbon monoxide, hydrogen, carbon dioxide and methane. This is achieved by reacting the material at high temperatures , without combustion, with a controlled amount of oxygen and/or steam...
. This residue contained large amounts of coronene
Coronene
Coronene is a polycyclic aromatic hydrocarbon 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...
and ovalene
Ovalene
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....
. After these were extracted and identified, a reddish residue remained, which was sparingly soluble in organic solvents. Elemental analysis indicated that it was most likely the condensed dimer of coronene
Coronene
Coronene is a polycyclic aromatic hydrocarbon 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...
.
Dicoronylene was later discovered to occur as a by-product of the catalytic hydrocracking used in petroleum processing. It is formed when two coronene
Coronene
Coronene is a polycyclic aromatic hydrocarbon 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...
molecules fuse. It is estimated that catalytical hydrocracking produces several hundred metric tons of dicoronylene worldwide per year, making it the most prevalent large PAH. In this process, the analogous 18-ring PAH formed from coronene and ovalene is also formed in 1% to 20% proportions. It is purple in color.
Properties
The formation of dicoronylene in hydrocracking reactors is a serious problem because its low solubility make it precipitate in any cooler part of the reactor flow path. This causes plugging of flow lines that require periodic shutdown and removal of the reddish deposits. Dicoronylene is also a constituent of cokePetroleum coke
Petroleum coke is a carbonaceous solid derived from oil refinery coker units or other cracking processes. Other coke has traditionally been derived from coal....
formed on hydrocracking catalysts, which reduces their activity.
Thermal pyrolysis
Pyrolysis
Pyrolysis is a thermochemical decomposition of organic material at elevated temperatures without the participation of oxygen. It involves the simultaneous change of chemical composition and physical phase, and is irreversible...
of coronene
Coronene
Coronene is a polycyclic aromatic hydrocarbon 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...
shows masses of dicoronylene and the condensed trimer, tetramer, and pentamer in the mass spectrum
Mass spectrum
A mass spectrum is an intensity vs. m/z plot representing a chemical analysis. Hence, the mass spectrum of a sample is a pattern representing the distribution of ions by mass in a sample. It is a histogram usually acquired using an instrument called a mass spectrometer...
of the black product. These larger coronene condensates are black in color.
Dicoronylene is moderately soluble in 1,2,4-trichlorobenzene
1,2,4-Trichlorobenzene
1,2,4-Trichlorobenzene is an organic compound used as a solvent, and is one of the best known solvents used to dissolve fullerenes and pentacene. It is a benzene derivative with three chlorine atoms substitutents, in the 1, 2 and 4 positions of the benzene ring.-See...
and these solutions have a greenish yellow 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...
. Unlike coronene, dicoronylene has symmetrical fluorescence excitation and emission spectra. It is virtually insoluble in most solvents.
Dicoronylene has been studied as a model for interstellar PAHs. Its large size and planarity have also shown promise as a chromatographic separation material.