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35-563: (Redirected from E-7 ) E7 , E07 , E-7 or E 7 may refer to: Science and engineering [ edit ] E7 liquid crystal mixture E 7 , the Lie group in mathematics E 7 polytope , in geometry E7 papillomavirus protein E7 European long distance path Transport [ edit ] EMD E7 , a diesel locomotive European route E07 , an international road Peugeot E7 ,

70-423: A leaving group , such as a halide , on an aromatic ring . Aromatic rings usually nucleophilic, but in the presence of electron-withdrawing groups aromatic compounds undergo nucleophilic substitution. Mechanistically, this reaction differs from a common S N 2 reaction , because it occurs at a trigonal carbon atom (sp hybridization ). Hydrogenation of arenes create saturated rings. The compound 1-naphthol

105-408: A benzene derivative and follow the benzene ring model, and non-benzoids that contain other aromatic cyclic derivatives. Aromatic compounds are commonly used in organic synthesis and are involved in many reaction types, following both additions and removals, as well as saturation and dearomatization. Heteroarenes are aromatic compounds, where at least one methine or vinylene (-C= or -CH=CH-) group

140-506: A chemistry typified by benzene " and "cyclically conjugated." The word "aromatic" originates from the past grouping of molecules based on odor, before their general chemical properties were understood. The current definition of aromatic compounds does not have any relation to their odor. Aromatic compounds are now defined as cyclic compounds satisfying Hückel's Rule . Aromatic compounds have the following general properties: Arenes are typically split into two categories - benzoids, that contain

175-452: A good candidate molecule to act as a basis for the earliest forms of life . In graphene the PAH motif is extended to large 2D sheets. Aromatic ring systems participate in many organic reactions. In aromatic substitution , one substituent on the arene ring, usually hydrogen, is replaced by another reagent. The two main types are electrophilic aromatic substitution , when the active reagent

210-603: A hackney cab PRR E7 , a steam locomotive Carbon Motors E7 , a police car E7 series , a Japanese high-speed train Nihonkai-Tōhoku Expressway and Akita Expressway (between Kawabe JCT and Kosaka JCT), route E7 in Japan Cheras–Kajang Expressway , route E7 in Malaysia Other uses [ edit ] Boeing E-7 , either: Boeing E-7 ARIA , the original designation assigned by

245-412: Is also an intermediate for the production of a host of other organic compounds such as emulsifiers , optical brighteners , crop protection products, and plastics . Biphenyl is insoluble in water, but soluble in typical organic solvents . The biphenyl molecule consists of two connected phenyl rings . Biphenyl is a solid at room temperature, with a melting point of 69.2 °C (156.6 °F). In

280-402: Is an electrophile, and nucleophilic aromatic substitution , when the reagent is a nucleophile. In radical-nucleophilic aromatic substitution , the active reagent is a radical . An example of electrophilic aromatic substitution is the nitration of salicylic acid , where a nitro group is added para to the hydroxide substituent: Nucleophilic aromatic substitution involves displacement of

315-429: Is aromatic, though strain within the structure causes a slight deviation from the precisely planar structure necessary for aromatic categorization. Another example of a non-benzylic monocyclic arene is the cyclopropenyl (cyclopropenium cation), which satisfies Hückel's rule with an n equal to 0. Note, only the cationic form of this cyclic propenyl is aromatic, given that neutrality in this compound would violate either

350-417: Is completely reduced to a mixture of decalin -ol isomers . The compound resorcinol , hydrogenated with Raney nickel in presence of aqueous sodium hydroxide forms an enolate which is alkylated with methyl iodide to 2-methyl-1,3-cyclohexandione: In dearomatization reactions the aromaticity of the reactant is lost. In this regard, the dearomatization is related to hydrogenation. A classic approach

385-446: Is different from Wikidata All article disambiguation pages All disambiguation pages E7 liquid crystal mixture It has a distinctively pleasant smell. Biphenyl is an aromatic hydrocarbon with a molecular formula (C 6 H 5 ) 2 . It is notable as a starting material for the production of polychlorinated biphenyls (PCBs), which were once widely used as dielectric fluids and heat transfer agents. Biphenyl

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420-494: Is fairly non-reactive, which is the basis of its main application: in a eutectic mixture with diphenyl ether , as a heat transfer agent. This mixture is stable to 400 °C. Biphenyl does undergo sulfonation which, followed by base hydrolysis, produces p -hydroxybiphenyl and p , p ′-dihydroxybiphenyl, which are useful fungicides. In other substitution reactions, it undergoes halogenation. Polychlorinated biphenyls were once popular pesticides. Lithium biphenyl contains

455-711: Is part of the active group in the antibiotic oritavancin . Biphenyl prevents the growth of molds and fungus , and is therefore used as a preservative ( E230 , in combination with E231, E232 and E233), particularly in the preservation of citrus fruits during transportation. It is no longer approved as a food additive in the European Union. Biphenyl is mildly toxic, but can be degraded biologically by conversion into nontoxic compounds. Some bacteria are able to hydroxylate biphenyl and its polychlorinated biphenyls (PCBs). Aromatic hydrocarbon Aromatic compounds or arenes usually refers to organic compounds "with

490-416: Is produced industrially as a byproduct of the dealkylation of toluene to produce methane : The other principal route is by the oxidative dehydrogenation of benzene : Annually 40,000,000 kg are produced by these routes. In the laboratory, biphenyl can also be synthesized by treating phenylmagnesium bromide with copper(II) salts. It can also be prepared using diazonium salts . When aniline

525-422: Is replaced by a heteroatom : oxygen , nitrogen , or sulfur . Examples of non-benzene compounds with aromatic properties are furan , a heterocyclic compound with a five-membered ring that includes a single oxygen atom, and pyridine , a heterocyclic compound with a six-membered ring containing one nitrogen atom. Hydrocarbons without an aromatic ring are called aliphatic . Approximately half of compounds known in

560-508: Is the simplest example of a PAH. PAHs occur in oil , coal , and tar deposits, and are produced as byproducts of fuel burning (whether fossil fuel or biomass). As pollutants, they are of concern because some compounds have been identified as carcinogenic , mutagenic , and teratogenic . PAHs are also found in cooked foods. Studies have shown that high levels of PAHs are found, for example, in meat cooked at high temperatures such as grilling or barbecuing, and in smoked fish. They are also

595-712: Is treated with NaNO 2 +dilute HCl at 5°C, it yields benzene diazonium chloride. When this is further reacted with benzene, biphenyl is formed. This is known as the Gomberg–Bachmann reaction . Ph − NH 2 → T =273-278K NaNO 2 (aq), HCl Ph − N 2 + → Ph-H, Δ Ph − Ph {\displaystyle {\ce {Ph-NH2->[{\text{NaNO}}_{2}{\text{(aq), HCl}}][T{\text{=273-278K}}]Ph-N2+->[{\text{Ph-H, Δ}}]Ph-Ph}}} Lacking functional groups, biphenyl

630-811: The Suzuki-Miyaura reaction and the Ullmann reaction . Polychlorinated biphenyls were once used as cooling and insulating fluids and polybrominated biphenyls are flame retardants . The biphenyl motif also appears in drugs such as diflunisal and telmisartan . The abbreviation E7 stands for a liquid crystal mixture consisting of several cyanobiphenyls with long aliphatic tails used commercially in liquid crystal displays ( 5CB , 7CB , 8OCB and 5CT ). A variety of benzidine derivatives are used in dyes and polymers. Research into biphenyl liquid crystal candidates mainly focuses on molecules with highly polar heads (for example cyano or halide groups) and aliphatic tails. It

665-400: The radical anion , which is highly reducing (-3.1 V vs Fc ). Several solvates of alkali metal salts of biphenyl anion have been characterized by X-ray crystallography . These salts, usually prepared in situ, are versatile reducing agents. Lithium biphenyl offers some advantages relative to the related lithium naphthene . Related to Li/biphenyl is the derivative with tert -butyl groups on

700-479: The seventh octave E-7, the original designation for the EC-18 ARIA electronic warfare aircraft E7, a postcode district in the E postcode area for east London European Aviation Air Charter , by IATA airline designator Nokia E7 , a smart phone Samsung Galaxy E7 , a smart phone E07, a number station allegedly used by Russia , and nicknamed "The English Man" [REDACTED] Topics referred to by

735-455: The Morrison & Boyd textbook on organic chemistry. The proper use of the symbol is debated: some publications use it to any cyclic π system, while others use it only for those π systems that obey Hückel's rule . Some argue that, in order to stay in line with Robinson's originally intended proposal, the use of the circle symbol should be limited to monocyclic 6 π-electron systems. In this way

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770-806: The United States Air Force under the Mission Designation System to the EC-18B Advanced Range Instrumentation Aircraft. Boeing E-7 Wedgetail , the designation assigned by the Royal Australian Air Force to the Boeing 737 AEW&C (airborne early warning and control) aircraft. Economy 7 , an electricity tariff E-7 enlisted rank in the military of the United States E7, a musical note in

805-410: The benzene ring. Although benzylic arenes are common, non-benzylic compounds are also exceedingly important. Any compound containing a cyclic portion that conforms to Hückel's rule and is not a benzene derivative can be considered a non-benzylic aromatic compound. Of annulenes larger than benzene, [12]annulene and [14]annulene are weakly aromatic compounds and [18]annulene, Cyclooctadecanonaene ,

840-404: The biphenyl. Rotation about the single bond in biphenyl, and especially its ortho-substituted derivatives, is sterically hindered . For this reason, some substituted biphenyls show atropisomerism ; that is, the individual C 2 - symmetric -isomers are optically stable . Some derivatives, as well as related molecules such as BINAP , find application as ligands in asymmetric synthesis . In

875-409: The case of unsubstituted biphenyl, the equilibrium torsional angle is 44.4° and the torsional barriers are quite small, 6.0 kJ/mol at 0° and 6.5 kJ/mol at 90°. Adding ortho substituents greatly increases the barrier: in the case of the 2,2'-dimethyl derivative, the barrier is 17.4 kcal/mol (72.8 kJ/mol). Substituted biphenyls have many uses. They are prepared by various coupling reactions including

910-414: The circle symbol for a six-center six-electron bond can be compared to the Y symbol for a three-center two-electron bond . Benzene derivatives have from one to six substituents attached to the central benzene core. Examples of benzene compounds with just one substituent are phenol , which carries a hydroxyl group, and toluene with a methyl group. When there is more than one substituent present on

945-540: The gas phase the molecule exists in two enantiomorphic twisted forms with an angle between the planes of the two rings of 44.4°. In the room-temperature solid, biphenyl is crystalline with space group P2 1 /c, which does not allow for chiral crystals. Rather than there being a double-well potential entailing the two twisted conformations, the potential energy is minimized at zero twist. Biphenyl occurs naturally in coal tar , crude oil , and natural gas and can be isolated from these sources via distillation . It

980-414: The methyl and hydroxyl group are ortho-para directors, the ortho and para isomers are typically favoured. Xylenol has two methyl groups in addition to the hydroxyl group, and, for this structure, 6 isomers exist. Arene rings can stabilize charges, as seen in, for example, phenol (C 6 H 5 –OH), which is acidic at the hydroxyl (OH), as charge on the oxygen (alkoxide –O ) is partially delocalized into

1015-545: The octet rule or Hückel's rule . Other non-benzylic monocyclic arenes include the aforementioned heteroarenes that can replace carbon atoms with other heteroatoms such as N, O or S. Common examples of these are the six-membered pyrrole and five-membered pyridine , both of which have a substituted nitrogen Polycyclic aromatic hydrocarbons , also known as polynuclear aromatic compounds (PAHs) are aromatic hydrocarbons that consist of fused aromatic rings and do not contain heteroatoms or carry substituents . Naphthalene

1050-540: The ortho, para or meta positions, depending on the directivity of the current substituents to make more complex benzene derivatives, often with several isomers. Electron flow leading to re-aromatization is key in ensuring the stability of such products. For example, three isomers exist for cresol because the methyl group and the hydroxyl group (both ortho para directors) can be placed next to each other ( ortho ), one position removed from each other ( meta ), or two positions removed from each other ( para ). Given that both

1085-462: The ring itself. This represents the equivalent nature of the six carbon-carbon bonds all of bond order 1.5. This equivalency can also explained by resonance forms . The electrons are visualized as floating above and below the ring, with the electromagnetic fields they generate acting to keep the ring flat. The circle symbol for aromaticity was introduced by Sir Robert Robinson and his student James Armit in 1925 and popularized starting in 1959 by

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1120-494: The ring, their spatial relationship becomes important for which the arene substitution patterns ortho , meta , and para are devised. When reacting to form more complex benzene derivatives, the substituents on a benzene ring can be described as either activated or deactivated , which are electron donating and electron withdrawing respectively. Activators are known as ortho-para directors, and deactivators are known as meta directors. Upon reacting, substituents will be added at

1155-447: The same term This disambiguation page lists articles associated with the same title formed as a letter–number combination. If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=E7&oldid=1244417257 " Category : Letter–number combination disambiguation pages Hidden categories: Short description

1190-415: The year 2000 are described as aromatic to some extent. Aromatic compounds are pervasive in nature and industry. Key industrial aromatic hydrocarbons are benzene, toluene , Xylene called BTX. Many biomolecules have phenyl groups including the so-called aromatic amino acids . Benzene , C 6 H 6 , is the least complex aromatic hydrocarbon, and it was the first one defined as such. Its bonding nature

1225-408: Was first recognized independently by Joseph Loschmidt and August Kekulé in the 19th century. Each carbon atom in the hexagonal cycle has four electrons to share. One electron forms a sigma bond with the hydrogen atom, and one is used in covalently bonding to each of the two neighboring carbons. This leaves six electrons, shared equally around the ring in delocalized pi molecular orbitals the size of

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