Replacement nomenclature

The type of heteroatom is indicated by a prefix according to Table 1. As all prefixes end with the letter a, replacement nomenclature is also known as a nomenclature. Position and prefix for each heteroatom are written in front of the name of the corresponding hydrocarbon. This is derived from the heterocyclic system by replacing every heteroatom by CH2, CH or C  

Sequence and numbering of the heteroatoms follow the rules given in 2.1. The two compounds chosen as examples could also be named according to the Hantzsch-Widman system silole, 1,4,2-thiazasilane. 

position and prefix are put in front of the name of the corresponding hydrocarbon, but the numbering of the hydrocarbon is retained  

The Hantzsch-Widman nomenclature can only be applied to the first example and this then results in different numbering. 

Heterocyclic compounds in which a C-atom of the ring is part of a carbonyl group are named with the aid of indicated hydrogen as follows  

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There are several types of nomenclature systems that are recognized. Which type to use is sometimes obvious from the nature of the compound. Substitutive nomenclature, in general, is preferred because of its broad applicability, but radicofunctional, additive, and replacement nomenclature systems are convenient in certain situations. 

Complex linear polyamines are best designated by replacement nomenclature. These trivial names are retained aniline, benzidene, phenetidine, toluidine, and xylidine. 

Organic ring systems are named by replacement nomenclature. Three- to ten-membered mono-cyclic ring systems containing uncharged boron atoms may be named by the specialist nomenclature for heterocyclic systems. Organic derivatives are named as outlined for substitutive nomenclature. The complexity of boron nomenclature precludes additional details the text by Rigaudy and Klesney should be consulted. 

Linear polyethers derived from three or more molecules of aliphatic dihydroxy compounds, particularly when the chain length exceeds ten units, are most conveniently named by open-chain replacement nomenclature. For example, CH3CH2—O—CH2CH2—O—CH2CH3 could be 3,6-dioxaoctane or (2-ethoxy)ethoxyethane. 

The prefix sila- designates replacement of carbon by silicon in replacement nomenclature. Prefix names for radicals are formed analogously to those for the corresponding carbon-containing compounds. Thus silyl is used for SiH3—, silyene for —SiH2—, silylidyne for —SiH<, as well as trily, tetrayl, and so on for free valences(s) on ring structures. 

When a boron atom of a borane is replaced by a heteroelement, the compounds are called carbaboranes, phosphaboranes, thiaboranes, a2aboranes, etc, by an adaptation of organic replacement nomenclature. The numbering of the skeleton in heteroboranes is such that the heteroelement is given the lowest possible number consistent with the conventions of the parent borane. Thus C2B2H is dicarba- /(9j (9-pentaborane(5) and could occur as the 1,2-, 2,3-, or 1,5-isomeric forms (l,2-dicarba- /(9j (9-pentaborane(5) [23777-70-0] 2,3-dicarba- /(9j (9-pentaborane(5) [30396-61-3] and... 

There are 19, largely nonmetallic, elements encompassed by the Hantzsch-Widman system the prefixes to indicate them are shown in Table 2. These prefixes, all of which end in a (which may be lost by elision), are the same as those used in replacement nomenclature (Section 1.02.2.3). 

For bicyclic structures the von Baeyer name consists of the prefix bicyclo-, followed in square brackets by the numbers of carbon atoms separating the bridgeheads on the three possible routes from one bridgehead to the other, followed in turn by the name of the alkane (or other homogeneous hydride, or repeating unit hydride) containing the same number of atoms in the chain as the whole bicyclic skeleton (examples 55-57). Replacement nomenclature can be applied to hydrocarbon names (example 58). 

Meanwhile, the A convention combined with replacement nomenclature may be used to indicate the changed bonding number of the anionic site, and the suffix -ide appended, as shown in (202) and (203). Proposals for an anionic replacement prefix, analogous to the cationic -onia prefixes, are under consideration. 

Substitution of carbon atoms on the perimeter by heteroatoms is indicated according to replacement nomenclature, e.g. l,4-diaza[3.3.3]cyclazine (3). 

Replacement nomenclature relating the cyclic ether to the corresponding... 

The CRU is named using replacement nomenclature ( a nomenclature) [3,8], N.B. In replacement a nomenclature as conventionally applied to acyclic structures with several heteroatoms, terminal heteroatoms are not designated with a prefixes but are named as characteristic groups of the structure, i.e., as hydroxy, amino, carboxylic acid, etc. However, heteroatoms in such positions within the CRUs of ladder or spiro polymer molecules are not terminal units and the stmctures are not acyclic. Consequently, such atoms are designated with a prefixes, and thereby the simplicity afforded by the application of replacement nomenclature to polymer molecules is enhanced. 

Other minor systems are also in use. Some are traditional, and some are very restricted in their application. These include acid nomenclature (inorganic, for oxoacids and derivatives), replacement nomenclature (mainly organic, to denote replacement of skeletal atoms in a parent rather than replacement of hydrogen atoms — oxa-aza replacement is one variant), functional class nomenclature (this is again principally organic and involves the use of type names such as alcohol, acid and ether) and subtractive nomenclatures (such as organic-deoxy and inorganic-debor). These will all be referred to briefly as appropriate. 

The two most important methods for naming heterocyclic parent hydrides are the extended Hantzsch-Widman system and replacement nomenclature. 

Replacement nomenclature is used to name heteromonocycles that contain more than ten atoms. In developing a replacement name, carbon atoms are regarded as exchanged for heteroatoms. The non-detachable prefixes (Table 4.8) are used to indicate the exchange. Cycloalkane or annulene names are the bases for transformation into the name of a heterocycle. 

Heterocyclic systems, which can be regarded as formed by replacement of carbon atoms in the parents described above by heteroatoms, are named by replacement nomenclature. 

The known types of five-membered heterocycles are presented at the beginning of each main section. Possible structural types with all heteroatomic combinations conceivable are almost unbounded, their presentation here would be worthless and is therefore avoided. The nomenclature of these heterocycles is defined by lUPAC rules (both Hantzsch-Widmann and replacement nomenclature are used) which are adhered to throughout the chapter. 

The second approach for endocyclic N-PACs is to use replacement nomenclature, in which the term aza is a prefix to the corresponding PAH. The position of the N-atom in the fused-ring system of the PAH precedes the term aza. Thus, for example, quinoline is 1-azanaphthalene. We generally use this convention for three or more ring N-PACs with endocyclic nitrogen heteroatoms. 

Further substitution of the peripheral carbon atoms of the cyclazines by heteroatoms (N, S, etc.) is indicated in this chapter according to the replacement nomenclature system (aza, thia, etc.). Although, strictly, this runs contrary to the rules,lc since it is a heterocyclic, not a hydrocarbon, system which is replaced, the connection between closely related compounds can more clearly be seen. It should be noted that Chemical Abstracts employs the systematic fusion nomenclature I, for instance, is pyrrolo[2,l,5-cd]indolizine. 

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