Isocyclic compounds

Functional groups Acyclic compounds Isocyclic compounds Heterocyclic compounds Heteroatom type and number (n) ... 

The position of the entry for any compound is determined by that fragment of its structure which is classified latest in the Beilstein System. Thus, for example, a compound containing a heterocyclic ring, a carbocyclic ring and an aliphatic chain is classified as a heterocycle, irrespective of the other structural elements, since all heterocycles are ordered after acyclic and isocyclic compounds in the Beilstein System. This feature of the systematic classification of compounds is called the Principle of Latest Systematic Entry. 

In the chemistry of silicon, heterocycles are rings containing silicon atoms and one or more of another type of atom. Of the isocyclic compounds, four to seven-membered rings are known, while the existence of an eight-membered ring is probable. The same or similar ring sizes are expected for heterocyclic silicon compounds. 

Isocyclic compounds. For all aromatic molecules there is resonance between different electron configurations, the number of which becomes rapidly greater for larger molecules. In particular the number of possible so-called excited configurations increases, in which, analogous to the Dewar structures in benzene, one, two or more formal bonds are present. 

The chemistry of furfural is mainly determined by the aldehyde function and the heteroaromatic furan ring. Many chemical transformations are therefore similar to those of aromatic aldehydes. However, the aromatic character of the heterocycle is low when compared to isocyclic compounds such as benzene derivatives or other related heterocycles such as pyrroles and pyridines. Therefore, the furan ring also resembles to a diene which significantly enriches the chemistry of furfural [112]. Many applications of furfural to organic synthesis are reported in the literature... 

Cyclic compounds in which the ring is made up of atoms of one element only are called isocyclic compounds. If the ring consists of C-atoms only, then we speak of a carbocyclic compound, e.g. ... 

Bicyclooctane derivatives are also classified with the isocyclic compounds. An example of a material which has a nematic phase, in the temperature range 104-106 °C, is... 

Isocyclic compounds — Isocyclische Verbindungen 2.3.2.2 Semiquinones — Semichinone ... 

Isocyclic compounds — Isocyclische Vefbindungen 2.3.Z3 Ben2ene and hydrocarbon substituted benzenes — Benzol- und Kohlenwassetstoff-substituiette Benzole ... 

Isocyclic compounds — Isocyclische Vetbindungen 2.3.2.4.A.U Monosubstltuted mononittobenzenes ) — Einfach substituierte Mononitrobenzole )... 

J.2 Isocyclic compounds — Isocyclische Verbindungen 2. 2.5 Nitrile-, fonnyl-, acetyl-, silyl- and getmyl-substituted benzenes — Nitril-, formyl-, acetyl-, silyl- und germyl-subsdtuiette Benzole ... 

Isocyclic compounds — Isocyclische Verbindung en 2.3.2.6 Non condensed polycyclic isocyclic aromatic compounds — Nichtkondensierte polycyclische isocyclische Aromaten... 

Isocyclic compounds — IsocycUsche Verbindungen 2.3.2J Condensed isocyclic aromatic compounds — Kondensierte isocycUstdie Aromaten ... 

Isocyclic compounds — Isocyclische Verbitidungeti 2.4.2.3 Condensed aromatic compounds — Kondensierte Aromaten ... 

Isocychc compounds contain ring structures in which all the ring components are carbon atoms, as shown in Figure 2.1. There are millions of isocyclic compounds, including many naturally occurring compounds with a variety of uses. Many have tastes and/or smells and are used as sweeteners or flavourings or are present in specific crop types selected for that very property. Others have medicinal properties, the best known example of which is aspirin. 

Table 2.5. Isocyclic compounds of plant origin (based on Senese, 2004, with additions)...

Heterocyclic compoimds have ring structure(s) that, imlike isocyclic compounds, contain atoms of elements other than carbon (see Figure 2.1). There are millions of heterocyclic compoimds in existence, which can be divided into six groups, as defined by Beilstein (see Section 2.2 above) and as listed in Table 2.7. The groups are characterised by the number of noncarbon (= hetero ) atoms they contain. Commonly these are atoms of oxygen or nitrogen, which form stable cyclic combinations with carbon, especially in 5- and 6-membered rings. 

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