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T2 - Journal of Heterocyclic Chemistry
Nevertheless, the chemistry of heterocyclic compounds with ringsseven-membered or larger is much less developed than that of five- andsix-membered ring heterocycles, although these compounds are usually stable andsome of them have found practical application.
Thiophene, which is a sulfur containing heterocycle, occurs in naturein some plant products but its greater importance is as an ingredient insynthetic pharmaceuticals and dyestuffs.
JF - Journal of Heterocyclic Chemistry
The heme group of theoxygen-carrying protein hemoglobin and of related compounds such as myoglobin;the chlorophylls, which are the light-gathering pigments of green plants andother photosynthetic organisms; and vitamin B12 are all formed from fourpyrrole units joined in a larger ring system known as a porphyrin, such as thatof chlorophyll b, shown below.
Later in this book we willdiscuss several specific heterocyclic compounds that are very commonly used inorganic chemistry and we'll discuss their individual characteristics.
The figure above shows just a few single-ring heterocycliccompounds.
In general, synthetic methods and physical and chemical propertiesof the saturated and the partly unsaturated heterocyclic compounds closelyresemble those for their acyclic (noncyclic, or open-chain) analogs.
Thus, as shown in the following structural formulas,pyrrolidine is a saturated heterocyclic compound containing no double bond; 4-dihydrofuran is an unsaturated heterocyclic compound; andpyridine is a typical heterocyclic aromatic, or heteroaromatic, substance.
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The ones shown are simply 5 and 6 membered rings.
Substitution of one or more of the ring carbon atoms in themolecules of a carbocyclic compound with a heteroatom gives a heterocycliccompound.
N, O, S, B, Si) other than carbon, it is classified as heterocyclic
. [4.1.1]propellane [4.4.4]propellane assemblies of three carbocyclic rings, a six-membered quinonoid ring bonded at the 1,4-positions to odd-membered rings which differ in ring size by two.
Pyridine is one of the most common and best knownheterocycles.
hexahelicene Synonymous with . Synonymous with . Synonymous with .Heterocyclic compounds formally derived from by replacement of one or more methine (-C=) and/or vinylene (-CH=CH-) groups by trivalent or divalent heteroatoms, respectively, in such a way as to maintain the continuous -electron system characteristic of aromatic systems and a number of out-of-plane -electrons corresponding to the Hückel rule (4n + 2); an alternative term is hetarenes.
Such heterocycles arewell-known reactive intermediates.
Of the seven-membered ringcompounds, one-heteroatom heterocycles—azepines, oxepines, and thiepines—andtheir derivatives are the most comprehensively studied.
Synthesis of N -Heterocycles - Organic Chemistry Portal
Ciufolini, Eds., VCH, 1993.The hydrocarbon fulvalene and its derivatives formed by substitution (and by extension, analogues formed by replacement of one or more carbon atoms of the fulvalene skeleton by a heteroatom).The hydrocarbon fulvene and its derivatives formed by substitution (and by extension, analogues formed by replacement of one or more carbon atoms of the fulvene skeleton by a heteroatom).-Fused polycyclic or heteroaromatic compounds in which all rings (minimum five) are angularly arranged so as to give helically shaped molecules, which are thus chiral.
Heterocyclic Chemistry - MSU Chemistry
43 ff.Compounds composed solely of an even number of carbon atoms, which form a cage-like fused-ring polycyclic system with twelve five-membered rings and the rest six-membered rings.
Heterocyclic compound - Wikipedia
However, a lowering in the carbonyl absorption band was observed, from the expected 1730cm-1 to 1680cm-1 as a result of the contribution of the ionic structure 12 to the resonance stability of the compound 10 as shown below  .
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