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Aromatic Ring Current
An aromatic ring current is an effect observed in aromatic molecules such as benzene and naphthalene. If a magnetic field is directed perpendicular to the plane of the aromatic system, a ring current is induced in the delocalized π electrons of the aromatic ring.[1] This is a direct consequence of Ampère's law; since the electrons involved are free to circulate, rather than being localized in bonds as they would be in most non-aromatic molecules, they respond much more strongly to the magnetic field. The ring current creates its own magnetic field. Outside the ring, this field is in the same direction as the externally applied magnetic field; inside the ring, the field counteracts the externally applied field
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Ring Current
A ring current is an electric current carried by charged particles trapped in a planet's magnetosphere. It is caused by the longitudinal drift of energetic (10–200 keV) particles.Contents1 Earth's ring current 2 The ring current and geomagnetic storms 3 See also 4 ReferencesEarth's ring current[edit]Schematic view of the different current systems which shape the Earth's magnetosphere.Earth's ring current is responsible for shielding the lower latitudes of the Earth
Earth
from magnetospheric electric fields. It therefore has a large effect on the electrodynamics of geomagnetic storms. The ring current system consists of a band, at a distance of 3 to 8 RE,[1], which lies in the equatorial plane and circulates clockwise around the Earth
Earth
(when viewed from the north)
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Cyclopentadiene
Cyclopentadiene
Cyclopentadiene
is an organic compound with the formula C5H6. This colorless liquid has a strong and unpleasant odor. At room temperature, this cyclic diene dimerizes over the course of hours to give dicyclopentadiene via a Diels–Alder reaction. This dimer can be restored by heating to give the monomer. The compound is mainly used for the production of cyclopentene and its derivatives
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Cyclohexane
Cyclohexane
Cyclohexane
is a cycloalkane with the molecular formula C6H12 (the alkyl is abbreviated Cy).[5] Cyclohexane
Cyclohexane
is mainly used for the industrial production of adipic acid and caprolactam, which are precursors to nylon
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Cyclobutadiene
Cyclobutadiene
Cyclobutadiene
is an organic compound with the formula C4H4. It is very reactive owing to its tendency to dimerize. Although the parent compound has not been isolated, some substituted derivatives are robust and a single molecule of cyclobutadiene is quite stable. Since the compound degrades by a bimolecular process, the species can be observed by matrix isolation techniques at temperatures below 35 K. It is thought to adopt a rectangular, nonplanar structure.[1][2]Contents1 Structure and reactivity 2 Synthesis 3 Trapping 4 See also 5 ReferencesStructure and reactivity[edit] The compound is the prototypical antiaromatic hydrocarbon with 4 π-electrons. It is the smallest [n]-annulene ([4]-annulene)
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Lithium
Lithium
Lithium
(from Greek: λίθος, translit. lithos, lit. 'stone') is a chemical element with symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the lightest metal and the lightest solid element. Like all alkali metals, lithium is highly reactive and flammable, and is stored in mineral oil. When cut open, it exhibits a metallic luster, but moist air corrodes it quickly to a dull silvery gray, then black tarnish. It never occurs freely in nature, but only in (usually ionic) compounds, such as pegmatitic minerals which were once the main source of lithium
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Coordination Chemistry
In chemistry, a coordination complex consists of a central atom or ion, which is usually metallic and is called the coordination centre, and a surrounding array of bound molecules or ions, that are in turn known as ligands or complexing agents.[1][2][3] Many metal-containing compounds, especially those of transition metals, are coordination complexes.[4] A coordination complex whose centre is a metal atom is called a metal complex.Contents1 Nomenclature and terminology 2 History 3 Structures3.1 Geometry 3.2 Isomerism3.2.1 Stereoisomerism3.2.1.1 Cis–trans isomerism
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Hapticity
Hapticity
Hapticity
is the coordination of a ligand to a metal center via an uninterrupted and contiguous series of atoms.[1] The hapticity of a ligand is described with the Greek letter η ('eta'). For example, η2 describes a ligand that coordinates through 2 contiguous atoms. In general the η-notation only applies when multiple atoms are coordinated (otherwise the κ-notation is used). In addition, if the ligand coordinates through multiple atoms that are not contiguous then this is considered denticity [2] (not hapticity), and the κ-notation is used once again.[3] When naming complexes care should be taken not to confuse η with μ ('mu'), which relates to bridging ligands.[4][5]Contents1 History1.1 Historically important compounds where the ligands are described with hapticity2 Examples2.1 Electrons donated by "π- ligands" vs. hapticity3 Changes in hapticity 4 Hapticity
Hapticity
vs
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Cyclopentadienyl
Cyclopentadienyl can refer to Cyclopentadienyl anion, or cyclopentadienide, [C5H5]− Cyclopentadienyl radical, [C5H5]• Cyclopentadienyl complexThis set index page lists chemical compounds articles associated with the same name. If an intern
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Pyrrole
Pyrrole
Pyrrole
is a heterocyclic aromatic organic compound, a five-membered ring with the formula C4H4NH.[1] It is a colorless volatile liquid that darkens readily upon exposure to air
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Thiophene
Thiophene
Thiophene
is a heterocyclic compound with the formula C4H4S. Consisting of a planar five-membered ring, it is aromatic as indicated by its extensive substitution reactions. It is a colorless liquid with a benzene-like odor
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Furan
Furan
Furan
is a heterocyclic organic compound, consisting of a five-membered aromatic ring with four carbon atoms and one oxygen. Chemical compounds containing such rings are also referred to as furans. Furan
Furan
is a colorless, flammable, highly volatile liquid with a boiling point close to room temperature. It is soluble in common organic solvents, including alcohol, ether, and acetone, and is slightly soluble in water.[3] It is toxic and may be carcinogenic in humans. Furan
Furan
is used as a starting point to other speciality chemicals.[4]Contents1 History 2 Production2.1 Synthesis of furans3 Chemistry 4 Safety 5 See also 6 References 7 External linksHistory[edit] The name "furan" comes from the Latin
Latin
furfur, which means bran.[5] The first furan derivative to be described was 2-furoic acid, by Carl Wilhelm Scheele in 1780
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Tropylium
In organic chemistry, the tropylium ion is an aromatic species with a formula of [C7H7]+.[1] Its name derives from the molecule tropine (itself named for the molecule atropine). Salts of the tropylium cation can be stable, e.g., tropylium tetrafluoroborate. It can be made from cycloheptatriene (tropylidene) and bromine or phosphorus pentachloride.[2] It is a regular heptagonal, planar, cyclic ion; as well, it has 6 π-electrons (4n + 2, where n = 1), which fulfills Hückel's rule
Hückel's rule
of aromaticity. It can coordinate as a ligand to metal atoms.skeletal formulaball-and-stick modelspace-filling modelThe structure shown is a composite of seven resonance contributors in which each carbon atom carries part of the positive charge. In 1891 G
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Pentalene
Pentalene
Pentalene
is a polycyclic hydrocarbon composed of two fused cyclopentadiene rings.[1] It has chemical formula C8H6. It is antiaromatic, because it has 4n π electrons where n is any integer. For this reason it dimerizes even at temperatures as low as −100 °C.[2][3] The derivative 1,3,5-tri-tert-butylpentalene was synthesized in 1973.[4] 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.[1] Dilithium pentalenide was isolated in 1962, long before pentalene itself in 1997.[5] 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
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Magnetic Susceptibility
In electromagnetism, the magnetic susceptibility (Latin: susceptibilis, "receptive"; denoted χ) is one measure of the magnetic properties of a material. The susceptibility indicates whether a material is attracted into or repelled out of a magnetic field, which in turn has implications for practical applications. Quantitative measures of the magnetic susceptibility also provide insights into the structure of materials, providing insight into bonding and energy levels. If the magnetic susceptibility is greater than zero, the substance is said to be "paramagnetic"; the magnetization of the substance is higher than that of empty space. If the magnetic susceptibility is less than zero, the substance is "diamagnetic"; it tends to exclude a magnetic field from its interior
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Heptalene
Heptalene
Heptalene
is a polycyclic hydrocarbon with chemical formula C12H10, composed of two fused cycloheptatriene rings. It is an unstable, non-planar compound which is non-aromatic.[1][2] The dianion, however, satisfies Hückel's rule, is thermally stable, and is planar.[3] See also[edit]BenzocyclooctatetraeneReferences[edit]^ Gottarelli, Giovanni; Hansen, Hans-Jürgen; Spada, Gian Piero; Weber, Roland H. (1987). "A Liquid-Crystal Study of Heptalene". Helvetica Chimica Acta. 70 (2): 430. doi:10.1002/hlca.19870700222.  ^ Boyd, G.V. (1966). "The aromaticity of pentalene, heptalene and related bicyclic hydrocarbons". Tetrahedron. 22 (10): 3409. doi:10.1016/S0040-4020(01)92529-3.  ^ Oth, Jean F. M.; Müllen, Klaus; Königshofen, Heinrich; Wassen, Jürgen; Vogel, Emanuel (1974). "The Dianion of Heptalene". Helvetica Chimica Acta. 57 (8): 2387. doi:10.1002/hlca.19740570811. This article about a hydrocarbon is a stub
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