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Hexa-peri-hexabenzocoronene
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. Hexa-peri-hexabenzocoronene has been imaged by atomic force microscopy (AFM) providing the first example of a molecule in which differences in bond order and bond lengths of the individual bonds can be distinguished by a measurement in direct space. Supramolecular structures Various hexabenzocoronenes have been investigated in supramolecular electronics. 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 u ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coronene
Coronene (also known as superbenzene and cyclobenzene) is a polycyclic aromatic hydrocarbon (PAH) comprising seven peri-fused benzene rings. Its chemical formula is . 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. Occurrence and synthesis 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 crea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Supramolecular 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. In supramolecular electronics, assemblies of pi-conjugated systems on the 5 to 100 nanometer length scale are prepared by molecular self-assembly with the aim to fit these structures between electrodes. With single-molecules as researched in molecular electronics at the 5 nanometer scale this would be impractical. Nanofibers can be prepared from polymers such as polyaniline and polyacetylene 12. Chiral oligo(p-phenylenevinylene)s self-assemble in a controlled fashion into (helical) wires 3. An example of actively researched compounds in this field are certain coronenes. References * 1 ''Chemistry: Material marriage in electronics'' E. W. Meijer, Albert P. H. J. Schenning Nature 419, 353-354 (26 Sep 2002) * 2 ''Supramolecular electronics; nanowires from self-asse ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atomic-force Microscopy
Atomic force microscopy (AFM) or scanning force microscopy (SFM) is a very-high-resolution type of scanning probe microscopy (SPM), with demonstrated resolution on the order of fractions of a nanometer, more than 1000 times better than the optical diffraction limit. Overview Atomic force microscopy (AFM) is a type of scanning probe microscopy (SPM), with demonstrated resolution on the order of fractions of a nanometer, more than 1000 times better than the optical diffraction limit. The information is gathered by "feeling" or "touching" the surface with a mechanical probe. Piezoelectric elements that facilitate tiny but accurate and precise movements on (electronic) command enable precise scanning. Despite the name, the Atomic Force Microscope does not use the Nuclear force. Abilities The AFM has three major abilities: force measurement, topographic imaging, and manipulation. In force measurement, AFMs can be used to measure the forces between the probe and the sample as a f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oxidation
Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a decrease in the oxidation state. There are two classes of redox reactions: * ''Electron-transfer'' – Only one (usually) electron flows from the reducing agent to the oxidant. This type of redox reaction is often discussed in terms of redox couples and electrode potentials. * ''Atom transfer'' – An atom transfers from one substrate to another. For example, in the rusting of iron, the oxidation state of iron atoms increases as the iron converts to an oxide, and simultaneously the oxidation state of oxygen decreases as it accepts electrons released by the iron. Although oxidation reactions are commonly associated with the formation of oxides, other chemical species can serve the same function. In hydrogenation, C=C (and other) bond ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Iron(III) Chloride
Iron(III) chloride is the inorganic compound with the formula . Also called ferric chloride, it is a common compound of iron in the +3 oxidation state. The anhydrous compound is a crystalline solid with a melting point of 307.6 °C. The colour depends on the viewing angle: by reflected light the crystals appear dark green, but by transmitted light they appear purple-red. Structure and properties Anhydrous Anhydrous iron(III) chloride has the structure, with octahedral Fe(III) centres interconnected by two-coordinate chloride ligands. Iron(III) chloride has a relatively low melting point and boils at around 315 °C. The vapor consists of the dimer (like aluminium chloride) which increasingly dissociates into the monomeric (with D3h point group molecular symmetry) at higher temperature, in competition with its reversible decomposition to give iron(II) chloride and chlorine gas. Hydrates In addition to the anhydrous material, ferric chloride forms four hydrates. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electrocyclic Reaction
In organic chemistry, an electrocyclic reaction is a type of pericyclic rearrangement where the net result is one pi bond being converted into one sigma bond or vice versa. These reactions are usually categorized by the following criteria: * Reactions can be either photochemical or thermal. * Reactions can be either ring-opening or ring-closing (electrocyclization). * Depending on the type of reaction (photochemical or thermal) and the number of pi electrons, the reaction can happen through either a conrotatory or disrotatory mechanism. * The type of rotation determines whether the cis or trans isomer of the product will be formed. Classical examples The Nazarov cyclization reaction is a named electrocyclic reaction converting divinylketones to cyclopentenones. A classic example is the thermal ring-opening reaction of 3,4-dimethylcyclobutene. The cis isomer exclusively yields whereas the trans isomer gives the trans,trans diene: This reaction course can be explained in a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hexaphenylbenzene
Hexaphenylbenzene is an aromatic compound composed of a benzene ring substituted with six phenyl rings. It is a colorless solid. The compound is the parent member of a wider class of hexaarylbenzenes, which are mainly of theoretical interest. Preparation It is prepared by heating tetraphenylcyclopentadienone and diphenylacetylene in benzophenone Benzophenone is the organic compound with the formula (C6H5)2CO, generally abbreviated Ph2CO. It is a white solid that is soluble in organic solvents. Benzophenone is a widely used building block in organic chemistry, being the parent diarylke ... or other high-temperature solvent. The reaction proceeds via a Diels-Alder reaction to give the hexaphenyldienone, which then eliminates carbon monoxide. : Together with 1,2,3,4-tetraphenylnaphthalene, hexaphenylbenzene forms by the chromium-catalyzed oligomerization of diphenylacetylene. Structure The stable conformation of this molecule has the phenyl rings rotated out of the pla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carbon Monoxide
Carbon monoxide ( chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simplest molecule of the oxocarbon family. In coordination complexes the carbon monoxide ligand is called carbonyl. It is a key ingredient in many processes in industrial chemistry. The most common source of carbon monoxide is the partial combustion of carbon-containing compounds, when insufficient oxygen or heat is present to produce carbon dioxide. There are also numerous environmental and biological sources that generate and emit a significant amount of carbon monoxide. It is important in the production of many compounds, including drugs, fragrances, and fuels. Upon emission into the atmosphere, carbon monoxide affects several processes that contribute to climate change. Carbon monoxide has important biological roles across phylog ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alkyne
\ce \ce Acetylene \ce \ce \ce Propyne \ce \ce \ce \ce 1-Butyne In organic chemistry, an alkyne is an unsaturated hydrocarbon containing at least one carbon—carbon triple bond. The simplest acyclic alkynes with only one triple bond and no other functional groups form a homologous series with the general chemical formula . Alkynes are traditionally known as acetylenes, although the name ''acetylene'' also refers specifically to , known formally as ethyne using IUPAC nomenclature. Like other hydrocarbons, alkynes are generally hydrophobic. Structure and bonding In acetylene, the H–C≡C bond angles are 180°. By virtue of this bond angle, alkynes are rod-like. Correspondingly, cyclic alkynes are rare. Benzyne cannot be isolated. The C≡C bond distance of 121 picometers is much shorter than the C=C distance in alkenes (134 pm) or the C–C bond in alkanes (153 pm). : The triple bond is very strong with a bond strength of 839 kJ/mol. The sigma bond contri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diels–Alder Reaction
In organic chemistry, the Diels–Alder reaction is a chemical reaction between a Conjugated system, conjugated diene and a substituted alkene, commonly termed the Diels–Alder reaction#The dienophile, dienophile, to form a substituted cyclohexene derivative. It is the prototypical example of a pericyclic reaction with a concerted reaction, concerted mechanism. More specifically, it is classified as a thermally-allowed [4+2] cycloaddition with Woodward–Hoffmann rules, Woodward–Hoffmann symbol [π4s + π2s]. It was first described by Otto Diels and Kurt Alder in 1928. For the discovery of this reaction, they were awarded the Nobel Prize in Chemistry in 1950. Through the simultaneous construction of two new carbon–carbon bonds, the Diels–Alder reaction provides a reliable way to form six-membered rings with good control over the regio- and stereochemical outcomes. Consequently, it has served as a powerful and widely applied tool for the introduction of chemical complexity in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyclopentadienone
Cyclopentadienone is an organic compound with molecular formula In chemistry, a chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, ... C5H4O. The parent cyclopentadienone is rarely encountered, because it rapidly dimerizes. Many substituted derivatives are known, notably tetraphenylcyclopentadienone. Such compounds are used as ligands in organometallic chemistry. left, The Knölker complex, derived from a substituted cyclopentadienone, is a catalyst for transfer hydrogenation. Preparation Cyclopentadienone can be generated by the photolysis or pyrolysis of various substances (e.g. 1,2-benzoquinone), and then isolated in an matrix isolation, argon matrix at . It dimerizes readily upon thawing the matrix at . See also * Dienone References Ketones Fully conjugated nonaromatic rings {{ke ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Benzil
Benzil (i.e. Bz2, systematically known as 1,2-diphenylethane-1,2-dione) is the organic compound with the formula ( C6H5 CO)2, generally abbreviated ( PhCO)2. This yellow solid is one of the most common diketones. Its main use is as a photoinitiator in polymer chemistry.Hardo Siegel, Manfred Eggersdorfer "Ketones" in Ullmann's Encyclopedia of Industrial Chemistry Wiley-VCH, 2002 by Wiley-VCH, Weinheim. Structure The compound's most noteworthy structural feature is the long carbon-carbon bond of 1.54 Å, which indicates the absence of pi-bonding between the two carbonyl centers. The PhCO centers are planar, but the pair of benzoyl groups are twisted with respect to the other with a dihedral angle of 117°. In less hindered analogues ( glyoxal, biacetyl, oxalic acid derivatives), the (RCO)2 group adopts a planar, anti-conformation. Applications Most benzil can be used as a photoinitiator in the free-radical curing of polymer networks. It absorbs ultraviolet radiation at ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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