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Heteropentalene
Heteropentalenes are class of heterocyclic compound. Heteropentalenes have one, two or more heteroatoms on the ring. It consists of two pentagonal rings. Heteropentalenes with 10 pi electrons show aromaticity. Some of heteropentalenes are mesomeric betaines. However those heteropentalenes are not mesoionic See also *Benzimidazole * Diazapentalene *Indole *Mesomeric betaine Mesomeric betaines are dipolar heterocyclic compounds in which both the negative and the positive charges are delocalized. Examples are mesoionic compounds and heteropentalenes (e.g. diazapentalenes). Heteropentalenes are not mesoionic In ch ... * Trithiapentalene References {{Reflist Heterocyclic compounds with 2 rings Simple aromatic rings ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mesomeric Betaine
Mesomeric betaines are dipolar heterocyclic compounds in which both the negative and the positive charges are delocalized. Examples are mesoionic compounds and heteropentalenes (e.g. diazapentalenes). Heteropentalenes are not mesoionic In chemistry, mesoionic compounds are one in which a heterocyclic structure is dipolar and where both the negative and the positive charges are delocalized. A completely uncharged structure cannot be written and mesoionic compounds cannot be rep .... References {{reflist Heterocyclic compounds Aromatic compounds ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mesomeric Betaine
Mesomeric betaines are dipolar heterocyclic compounds in which both the negative and the positive charges are delocalized. Examples are mesoionic compounds and heteropentalenes (e.g. diazapentalenes). Heteropentalenes are not mesoionic In chemistry, mesoionic compounds are one in which a heterocyclic structure is dipolar and where both the negative and the positive charges are delocalized. A completely uncharged structure cannot be written and mesoionic compounds cannot be rep .... References {{reflist Heterocyclic compounds Aromatic compounds ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heterocyclic Compound
A heterocyclic compound or ring structure is a cyclic compound that has atoms of at least two different elements as members of its ring(s). Heterocyclic chemistry is the branch of organic chemistry dealing with the synthesis, properties, and applications of these heterocycles. Examples of heterocyclic compounds include all of the nucleic acids, the majority of drugs, most biomass (cellulose and related materials), and many natural and synthetic dyes. More than half of known compounds are heterocycles. 59% of US FDA-approved drugs contain nitrogen heterocycles. Classification The study of heterocyclic chemistry focuses especially on unsaturated derivatives, and the preponderance of work and applications involves unstrained 5- and 6-membered rings. Included are pyridine, thiophene, pyrrole, and furan. Another large class of heterocycles refers to those fused to benzene rings. For example, the fused benzene derivatives of pyridine, thiophene, pyrrole, and furan are quinol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heteroatom
In chemistry, a heteroatom () is, strictly, any atom that is not carbon or hydrogen. Organic chemistry In practice, the term is usually used more specifically to indicate that non-carbon atoms have replaced carbon in the backbone of the molecular structure. Typical heteroatoms are nitrogen (N), oxygen (O), sulfur (S), phosphorus (P), chlorine (Cl), bromine (Br), and iodine (I), as well as the metals lithium (Li) and magnesium (Mg). Proteins It can also be used with highly specific meanings in specialised contexts. In the description of protein structure, in particular in the Protein Data Bank file format, a heteroatom record (HETATM) describes an atom as belonging to a small molecule cofactor rather than being part of a biopolymer chain. Zeolites In the context of zeolites, the term ''heteroatom'' refers to partial isomorphous substitution of the typical framework atoms (silicon, aluminium, and phosphorus) by other elements such as beryllium, vanadium, and chromium. The goal is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pentagonal
In geometry, a pentagon (from the Greek πέντε ''pente'' meaning ''five'' and γωνία ''gonia'' meaning ''angle'') is any five-sided polygon or 5-gon. The sum of the internal angles in a simple pentagon is 540°. A pentagon may be simple or self-intersecting. A self-intersecting ''regular pentagon'' (or ''star pentagon'') is called a pentagram. Regular pentagons A '' regular pentagon'' has Schläfli symbol and interior angles of 108°. A '' regular pentagon'' has five lines of reflectional symmetry, and rotational symmetry of order 5 (through 72°, 144°, 216° and 288°). The diagonals of a convex regular pentagon are in the golden ratio to its sides. Given its side length t, its height H (distance from one side to the opposite vertex), width W (distance between two farthest separated points, which equals the diagonal length D) and circumradius R are given by: :\begin H &= \frac~t \approx 1.539~t, \\ W= D &= \frac~t\approx 1.618~t, \\ W &= \sqrt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pi Electron
In chemistry, pi bonds (π bonds) are covalent chemical bonds, in each of which two lobes of an orbital on one atom overlap with two lobes of an orbital on another atom, and in which this overlap occurs laterally. Each of these atomic orbitals has an electron density of zero at a shared nodal plane that passes through the two bonded nuclei. This plane also is a nodal plane for the molecular orbital of the pi bond. Pi bonds can form in double and triple bonds but do not form in single bonds in most cases. The Greek letter π in their name refers to p orbitals, since the orbital symmetry of the pi bond is the same as that of the p orbital when seen down the bond axis. One common form of this sort of bonding involves p orbitals themselves, though d orbitals also engage in pi bonding. This latter mode forms part of the basis for metal-metal multiple bonding. Pi bonds are usually weaker than sigma bonds. The C-C double bond, composed of one sigma and one pi bond, has a bond ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mesoionic
In chemistry, mesoionic compounds are one in which a heterocyclic structure is dipolar and where both the negative and the positive charges are delocalized. A completely uncharged structure cannot be written and mesoionic compounds cannot be represented satisfactorily by any one mesomeric structure. Mesoionic compounds are a subclass of betaines. Examples are sydnones and sydnone imines (e.g. the stimulant mesocarb), münchnones, and mesoionic carbenes. The formal positive charge is associated with the ring atoms and the formal negative charge is associated either with ring atoms or an exocyclic nitrogen or other atom. These compounds are stable zwitterionic compounds and belong to nonbenzenoid aromatics. See also * Mesomeric betaine Mesomeric betaines are dipolar heterocyclic compounds in which both the negative and the positive charges are delocalized. Examples are mesoionic compounds and heteropentalenes (e.g. diazapentalenes). Heteropentalenes are not mesoionic In c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Benzimidazole
Benzimidazole is a heterocyclic aromatic organic compound. This bicyclic compound may be viewed as fused rings of the aromatic compounds benzene and imidazole. It is a colorless solid. Preparation Benzimidazole is produced by condensation of o-phenylenediamine with formic acid,. or the equivalent trimethyl orthoformate: :C6H4(NH2)2 + HC(OCH3)3 → C6H4N(NH)CH + 3 CH3OH 2-substituted derivatives are obtained when the condensation is conducted with aldehydes in place of formic acid, followed by oxidation.Robert A. Smiley "Phenylene- and Toluenediamines" in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim. Reactions Benzimidazole is a base: :C6H4N(NH)CH + H+ → [C6H4(NH)2CH]+ It can also be deprotonated with stronger bases: :C6H4N(NH)CH + LiH → Li [C6H4N2CH] + H2 The imine can be alkylated and also serves as a ligand in coordination chemistry. The most prominent benzimidazole complex features ''N''-ribosyl-dimethylbenzimidazole as found ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diazapentalene
In organic chemistry, a diazapentalene is any of the heterocyclic compounds having molecular formula C6H6N2 whose structure is two fused two pentagonal rings of six carbon atoms and two nitrogen atoms. That is, it is a heteropentalene, with two nitrogens substituted in for carbons. There are several different constitutional isomers. Each diazapentalene has 10 pi electrons and shows aromaticity. Some of the diazapentalenes are mesomeric betaines, however these diazapentalenes are not mesoionic. See also *pentalene *Diketopyrrolopyrrole dye Diketopyrrolopyrroles (DPPs) are organic dyes and pigments based on the heterocyclic dilactam 2,5-dihydropyrrolo ,4-''c''yrrole-1,4-dione, widely used in optoelectronics. DPPs were initially used as pigments in the painting industry (e.g. in automo ...( :de:Diketopyrrolopyrrol-Pigmente) References {{reflist Heterocyclic compounds with 2 rings Simple aromatic rings Nitrogen heterocycles ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Indole
Indole is an aromatic heterocyclic organic compound with the formula C8 H7 N. It has a bicyclic structure, consisting of a six-membered benzene ring fused to a five-membered pyrrole ring. Indole is widely distributed in the natural environment and can be produced by a variety of bacteria. As an intercellular signal molecule, indole regulates various aspects of bacterial physiology, including spore formation, plasmid stability, resistance to drugs, biofilm formation, and virulence. The amino acid tryptophan is an indole derivative and the precursor of the neurotransmitter serotonin. General properties and occurrence Indole is a solid at room temperature. It occurs naturally in human feces and has an intense fecal odor. At very low concentrations, however, it has a flowery smell, and is a constituent of many perfumes. It also occurs in coal tar. The corresponding substituent is called indolyl. Indole undergoes electrophilic substitution, mainly at position 3 (see diagra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trithiapentalene
Trithiapentalene is an organic chemistry, organic bicyclic molecule containing two sulfur heterocycles. Its 10-π aromatic structure is similar to naphthalene. There has been a literature dispute about whether the connectivity among the three sulfur atoms is a case of rapid tautomerization between two valence tautomers or a Three-center four-electron bond, 3-center 4-electron bond. The reactions have been little studied. It forms a dinickel complex upon reaction with bis(allyl)nickel. See also * Dithiolium salt References {{Reflist Sulfur heterocycles Aromatic compounds Heterocyclic compounds with 2 rings ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heterocyclic Compounds With 2 Rings
A heterocyclic compound or ring structure is a cyclic compound that has atoms of at least two different elements as members of its ring(s). Heterocyclic chemistry is the branch of organic chemistry dealing with the synthesis, properties, and applications of these heterocycles. Examples of heterocyclic compounds include all of the nucleic acids, the majority of drugs, most biomass (cellulose and related materials), and many natural and synthetic dyes. More than half of known compounds are heterocycles. 59% of US FDA-approved drugs contain nitrogen heterocycles. Classification The study of heterocyclic chemistry focuses especially on unsaturated derivatives, and the preponderance of work and applications involves unstrained 5- and 6-membered rings. Included are pyridine, thiophene, pyrrole, and furan. Another large class of heterocycles refers to those fused to benzene rings. For example, the fused benzene derivatives of pyridine, thiophene, pyrrole, and furan are quinol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
