Ring compounds systematic naming

Indole is a heteroaromatic compound consisting of a fused benzene and pyrrole ring, specifically ben2o[ ]pyrrole. The systematic name, IJT-indole (1) distinguishes it from the less stable tautomer 3JT-indole [271-26-1] (2). Iff-Indole [120-72-9] is also more stable than the isomeric ben2o[ ] pyrrole, which is called isoindole, (2H, (3) and IH (4)). A third isomer ben2o[i ]pyrrole is a stable compound called indoli2idine [274-40-8] (5). 

Completely trivial names continue in use for good reasons, of which an important one is the need for a simple name for frequent communication concerning a commonly encountered compound or structure. For obscure compounds there is surely neither need nor desirability to perpetuate trivial names, and coining new trivial names is almost never justified. Let us, however, consider purine , the trivial name for what might more systematically be named imidazo[5,4-ring system is so important in biochemistry that exclusive use of one of the systematic names would be intolerable. If the name purine were not available, another short trivial name would inevitably be coined, or even an acronym ( IP or TAP ). It is better to retain the name sanctioned by roughly a century of use, and benefit from a link in comprehension with the past. 

Structural Formula of Systematic Name of Ring Compound Prepared System... 

This class of tricyclic compound is dominated by the 377-pyrrolizines (systematically named 3//-pyrrolo[l,2- ]-pyrroles) and related systems, which are fused to another six-membered heterocyclic ring (Figure 1). 

The nomenclature of the family of compounds to be discussed below has for long been the cause of much confusion. The systematic name for a six-membered ring containing one sulfur atom is thiin, but Chemical Abstracts uses the name thiopyran, while many earlier publications have used the replacement nomenclature thiapyran (which is strictly inaccurate as thia implies replacement of carbon, rather than oxygen, by sulfur). Throughout this chapter the terms thiopyran and thiin will be used interchangeably, while thiadecalin nomenclature will be found convenient for the perhydrobenzothiopyran systems. 

American practice is to use the terminations -ane for saturated and ene for unsaturated compounds in both the hydrocarbon and the heterocyclic series. British usage is essentially the same for hydrocarbons, but for heterocyclic molecules the final e is omitted in fact, a terminal e is used in general only for hydrocarbons, bases, and the five-membered ring ending ole. This leads in particular to some differences in the spelling of both trivial and systematic names for one-ring heterocycles e.g., thiophen, oxiren, dioxaphospholan (British) thiophene, oxirene, dioxaphospholane (American). 

Six-membered sulfur heterocyclic compounds are based on four molecules 2//-thiopyran 6, 4//-thiopyran 7, thiopyrylium 8, and l //-thiopyran 9 which is formally named as lA4-thiopyran and also referred to as thiabenzene. The systematic name thiin for six-membered rings containing a sulfur atom is infrequently used. 

Additionally, for comparison purposes, included herein are systematic names for the mathematically simplest ring overlap compound (Figure 9) ... 

Compounds are systematically named in the density tables as alky (alkenyl, alkynyl, etc.) derivatives of benzene in the style <side chains>benzene. Side chains consist of one or more alkyl (alkenyl, alkynyl, etc.) radicals attached to the benzene ring. Thus names such as butyl, pentyl, heptyl refer to saturated straight chain radicals. Unsaturated side chains are named as radicals from the corresponding alkene, alkadiene, alkyne, etc. Examples are ethenyl, (1-propenyl), (2-butenyl), (2,3-pentadienyl), and (4-pentynyl). The numbers indicate the postion of the double and triple bonds. 

The final product of this chain of events—arachidonic acid—is one of the eicosanoids, so called because eicosa is Greek for twenty, and the systematic names for these compounds contain eicosanoic acid in some form. The leukotrienes resemble arachidonic acid most closely, the prostaglandins have a closed chain forming a five-membered ring, and the thromboxanes resemble the prostaglandins but have a broken chain. A)] are C20 compounds with the sites of the alkenes (C5, C8, Cl 1, and Cl 4) marked by functionality or some other structural feature. 

Because the.se systematic names are so unwieldy, organic chemists often assign a name to a polycyclic compound that is more descriptive of its shape and structure. Dodecahedrane is named because its 12 five-membered rings resemble a dodecahedron. Figure 4.4 shows the names and... 

Polycyclic compounds contain two or more rings that share two or more carbon atoms. We can illustrate the naming system with norbomane whose systematic name is bicycIo[2.2.1]heptane (a) heptane since it contains a total of seven carbon atoms (b) bicyclo, since it contains two rings, that is, breaking two carbon-... 

The only cyclic ethers that behave differently from open-chain ethers the three-membered-ring compounds called epoxides, or oxiranes. strain of the tbree-meml red ring gives epoxides unique chemical reach Ethylene oxide, the simplest epoxide, is an intermediate in the mam ture of both ethylene glycol, used for automobile antifreeze, and polyester mers. More than 4 million tons of ethylene oxide are produced each year the United States by air oxidation of ethylene over a silver oxide catalyst a SOO°C. This process is not useful for other epoxides, however, and is of littb value in the laboratory. Note that the name ethylene, oxide is not a systematie one because the -ene ending implies the presence of a double bond in the mol eculc. The name is frequently used, however, because ethylene oxide is deriva from ethylene by addition of an oxygen atom. Other simple epoxides are name similarly. The systematic name for ethylene oxide is 1,2-epoxyethane. 

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