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Pentalene
Pentalene is a polycyclic hydrocarbon composed of two fused cyclopentadiene rings. It has chemical formula . It is antiaromatic, because it has 4''n'' π electrons where ''n'' is any integer. For this reason it dimerizes even at temperatures as low as −100 °C. The derivative 1,3,5-tri-''tert''-butylpentalene was synthesized in 1973. Because of the ''tert''-butyl substituents this compound is thermally stable. Pentalenes can also be stabilized by benzannulation for example in the compounds benzopentalene and dibenzopentalene. Dilithium pentalenide was isolated in 1962, long before pentalene itself in 1997. It is prepared from reaction of dihydropentalene (pyrolysis of an isomer of dicyclopentadiene) with ''n''-butyllithium in solution and forms a stable salt. In accordance with its structure proton NMR shows 2 signals in a 2 to 1 ratio. The addition of two electrons removes the antiaromaticity; it becomes a planar 10π-electron aromatic species and is thus a bicyclic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acepentalene
Acepentalene is a tricyclic anti-aromatic compound. Its molecular formula is . It consists of three five-membered rings fused across three of the five carbon atoms. The central carbon atom in acepentalene is part of all three rings. There are formally five double bonds in acepentalene, so that the molecule formally contains four double bonds on the exterior, and one double bond from the central carbon to the exterior of the ring system. The acepentalene dianion, which can be stabilized by two lithium Lithium (from el, λίθος, lithos, lit=stone) is a chemical element with the symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the least dense metal and the least dense solid ... atoms, is more stable. The radical (chemistry), radical anion is also known. The dianion was first synthesized by reacting triquinacene with N-Butyllithium, n-butyllithium and potassium tert-amylate (also called potassium t-pentoxide) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dibenzopentalene
Dibenzopentalene (dibenzo ,eentalene or dibenzo ,fentalene) is an organic compound and a hydrocarbon with formula C16H10. It is of some scientific interest as a stable derivative of the highly reactive antiaromatic pentalene by benzannulation. The first derivative was synthesised in 1912 by Brand. The parent compound was reported in 1952. The NICS value for the 5-membered rings is estimated at 7.4 ppm and that of the six-membered rings -9.8 ppm. Aromatic dicationic salts can be obtained by reaction with antimony pentafluoride in sulfuryl chloride. The dianion forms by reduction with lithium metal or deprotonation of 5,10-dihydroindeno ,1-''a''ndene with two equivalents of butyllithium Butyllithium may refer to one of 5 isomeric organolithium reagents of which 3 are commonly used in chemical synthesis: * ''n''-Butyllithium, abbreviated BuLi or nBuLi * ''sec''-Butyllithium, abbreviated ''sec''-BuLi or sBuLi, has 2 stereoisomers, .... The aromatic nature of the dianion has been ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pentalenide
Pentalene is a polycyclic hydrocarbon composed of two fused cyclopentadiene rings. It has chemical formula . It is antiaromatic, because it has 4''n'' π electrons where ''n'' is any integer. For this reason it dimerizes even at temperatures as low as −100 °C. The derivative 1,3,5-tri-''tert''-butylpentalene was synthesized in 1973. Because of the ''tert''-butyl substituents this compound is thermally stable. Pentalenes can also be stabilized by benzannulation for example in the compounds benzopentalene and dibenzopentalene. Dilithium pentalenide was isolated in 1962, long before pentalene itself in 1997. It is prepared from reaction of dihydropentalene (pyrolysis of an isomer of dicyclopentadiene) with ''n''-butyllithium in solution and forms a stable salt. In accordance with its structure proton NMR shows 2 signals in a 2 to 1 ratio. The addition of two electrons removes the antiaromaticity; it becomes a planar 10π-electron aromatic species and is thus a bicyclic ana ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antiaromatic Compounds
Antiaromaticity is a chemical property of a cyclic molecule with a π electron system that has higher energy, i.e., it is less stable due to the presence of 4n delocalised (π or lone pair) electrons in it, as opposed to aromaticity. Unlike aromatic compounds, which follow Hückel's rule ( ''n''+2π electrons) and are highly stable, antiaromatic compounds are highly unstable and highly reactive. To avoid the instability of antiaromaticity, molecules may change shape, becoming non-planar and therefore breaking some of the π interactions. In contrast to the diamagnetic ring current present in aromatic compounds, antiaromatic compounds have a paramagnetic ring current, which can be observed by NMR spectroscopy. Examples of antiaromatic compounds are pentalene (A), biphenylene (B), cyclopentadienyl cation (C). The prototypical example of antiaromaticity, cyclobutadiene, is the subject of debate, with some scientists arguing that antiaromaticity is not a major factor contributing t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heptalene
Heptalene is a polycyclic hydrocarbon with chemical formula , composed of two fused cycloheptatriene rings. It is an unstable, non-planar compound which is non-aromatic. The dianion, however, satisfies Hückel's rule In organic chemistry, Hückel's rule predicts that a planar ring molecule will have aromatic properties if it has 4''n'' + 2 π electrons, where ''n'' is a non-negative integer. The quantum mechanical basis for its formulation was f ..., is thermally stable, and is planar. See also * Benzocyclooctatetraene References {{Hydrocarbon-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
International Union Of Pure And Applied Chemistry
The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations working for the advancement of the chemical sciences, especially by developing nomenclature and terminology. It is a member of the International Science Council (ISC). IUPAC is registered in Zürich, Switzerland, and the administrative office, known as the "IUPAC Secretariat", is in Research Triangle Park, North Carolina, United States. This administrative office is headed by IUPAC's executive director, currently Lynn Soby. IUPAC was established in 1919 as the successor of the International Congress of Applied Chemistry for the advancement of chemistry. Its members, the National Adhering Organizations, can be national chemistry societies, national academies of sciences, or other bodies representing chemists. There are fifty-four National Adhering Organizations and three Associate National Adhering Organizations. IUPAC's Inter-divisional Committee ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyclooctatetraene
1,3,5,7-Cyclooctatetraene (COT) is an unsaturated derivative of cyclooctane, with the formula C8H8. It is also known as nnulene. This polyunsaturated hydrocarbon is a colorless to light yellow flammable liquid at room temperature. Because of its stoichiometric relationship to benzene, COT has been the subject of much research and some controversy. Unlike benzene, C6H6, cyclooctatetraene, C8H8, is not aromatic, although its dianion, ( cyclooctatetraenide), is. Its reactivity is characteristic of an ordinary polyene, i.e. it undergoes addition reactions. Benzene, by contrast, characteristically undergoes substitution reactions, not additions. History 1,3,5,7-Cyclooctatetraene was initially synthesized by Richard Willstätter in Munich in 1905 using pseudopelletierine as the starting material and the Hofmann elimination as the key transformation: : Willstätter noted that the compound did not exhibit the expected aromaticity. Between 1939 and 1943, chemists throug ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Octalene
Octalene is a polycyclic hydrocarbon composed of two fused cyclooctatetraene rings. Anions Octalene can be readily reduced by lithium to a dianion and, unusually for such a small molecule, a tetraanion .Müllen, K., Oth, J. F. M., Engels, H.-W. and Vogel, E. (1979), Dianion and Tetraanion Octalene. Angew. Chem. Int. Ed. Engl., 18: 229–231. doi:10.1002/anie.197902291 The di-anion has its two negative charges in one ring, converting that ring into a 10-pi electron aromatic system similar to the di-anion of cyclooctatetraene. In the 18-pi electron tetra-anion, both rings effectively have access to 10 pi electrons, leading to a planar, bicyclic aromatic structure analogous to that of naphthalene. See also *Propalene * Benzyne *Pentalene * Heptalene *Butalene Butalene is a polycyclic hydrocarbon composed of two fused cyclobutadiene rings. A reported possible synthesis of it involves an elimination reaction from a Dewar benzene derivative. The structure itself can be envisione ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Butalene
Butalene is a polycyclic hydrocarbon composed of two fused cyclobutadiene rings. A reported possible synthesis of it involves an elimination reaction from a Dewar benzene derivative. The structure itself can be envisioned as benzene with an internal bridge, and calculations indicate it is somewhat less stable than the open 1,4-didehydrobenzene biradical, the valence isomer in which that bridged bond is broken. Structure and bonding Ab initio calculations indicate butalene has a planar geometry and, in keeping with a planar structure with 6 π-electron configuration, is aromatic. Thus, the most significant π bonding interactions involve conjugation around the periphery of the whole six-atom structure, similar to benzene, rather than cross-ring resonance along the bridging bond. Significant resonance around one or the other four-membered ring alone would be a less-stable antiaromatic form, as is seen in cyclobutadiene itself. See also *Propalene *Pentalene Pentalene ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Benzocyclobutadiene
Benzocyclobutadiene is the simplest polycyclic hydrocarbon, being composed of an aromatic benzene ring fused to an anti-aromatic cyclobutadiene ring. It has chemical formula . Though the benzene ring is stabilized by aromaticity, the cyclobutadiene portion has a destabilizing effect. This results into it being a non-aromatic compound - neither behaving as aromatic nor an antiaromatic one. For this reason, benzocyclobutadiene will readily dimerize or polymerize and it reacts as a dienophile in Diels-Alder reactions. Benzocyclobutadiene is used in the production of the pharmaceutical drug naflocort. See also *Pentalene Pentalene is a polycyclic hydrocarbon composed of two fused cyclopentadiene rings. It has chemical formula . It is antiaromatic, because it has 4''n'' π electrons where ''n'' is any integer. For this reason it dimerizes even at temperatures as ... References {{reflist Polycyclic aromatic hydrocarbons Bicyclic compounds Four-membered rings ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyclooctatetraene
1,3,5,7-Cyclooctatetraene (COT) is an unsaturated derivative of cyclooctane, with the formula C8H8. It is also known as nnulene. This polyunsaturated hydrocarbon is a colorless to light yellow flammable liquid at room temperature. Because of its stoichiometric relationship to benzene, COT has been the subject of much research and some controversy. Unlike benzene, C6H6, cyclooctatetraene, C8H8, is not aromatic, although its dianion, ( cyclooctatetraenide), is. Its reactivity is characteristic of an ordinary polyene, i.e. it undergoes addition reactions. Benzene, by contrast, characteristically undergoes substitution reactions, not additions. History 1,3,5,7-Cyclooctatetraene was initially synthesized by Richard Willstätter in Munich in 1905 using pseudopelletierine as the starting material and the Hofmann elimination as the key transformation: : Willstätter noted that the compound did not exhibit the expected aromaticity. Between 1939 and 1943, chemists throug ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
