Skeletal replacement nomenclature

Termination vowel for skeletal replacement nomenclature -oxa [0], -aza [N], -carba [C). -thia [S]... 

When at least four carbon atoms in an unbranched-chain parent hydrocarbon are replaced by heteroatoms, alike or different, and the terminal carbon atoms either remain or are replaced by P, As, Sb, Bi, Si, Ge, Sn, Pb, B, Al, Ga, In, or Tl, skeletal replacement nomenclature ( a nomenclature) may be used to indicate the heteroatoms (see Sections P-15.4 and P-21.2 of Ref. 1). 

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. 

Operations in which certain non-hydrogen atoms of parents are replaced by different atoms or groups, e.g. the skeletal replacements leading to a names in organic chemistry (see Sections P-13.2 and P-51.3 of Ref. 21), are usually considered as part of substitutive nomenclature and are also used in certain parts of inorganic chemistry. 

IR-6.2.4.1 Heteronuclear acyclic parent hydrides in general IR-6.2.4.2 Hydrides consisting of chains of alternating skeletal atoms IR-6.2.4.3 Heteronuclear monocyclic parent hydrides Hantzsch-Widman nomenclature IR-6.2.4.4 Skeletal replacement in boron hydrides IR-6.2.4.5 Heteronuclear polycyclic parent hydrides IR-6.3 Substitutive names of derivatives of parent hydrides IR-6.3.1 Use of suffixes and prefixes IR-6.3.2 Hydrogen substitution in boron hydrides IR-6.4 Names of ions and radicals derived from parent hydrides... 

Constructing a substitutive name generally involves the replacement of hydrogen atoms in a parent structure with other atoms or atom groups. Related operations, often considered to be part of substitutive nomenclature, are skeletal replacement (Section IR-6.2.4.1) and functional replacement in oxoacid parents (Section IR-8.6). Note that some operations in parent hydride-based nomenclature are not substitutive operations (e.g. formation of cations and anions by addition of H+ and H, respectively, cf. Sections IR-6.4.1 and IR-6.4.5). Names formed by the modifications of parent hydride names described in those sections are still considered part of substitutive nomenclature. 

Sometimes it may be necessary or preferable to consider a parent hydride in which several (four or more) skeletal carbon atoms of a hydrocarbon have been replaced by main group elements. In this method of skeletal replacement the heteroatoms are designated by the a terms of replacement nomenclature (Table X) cited in the order given by Table VI and preceded by the appropriate locant(s). The rules for locant numbering are specified in Section IR-6.2.4.1 and this nomenclature is fully described in Sections P-21.2 and P-22.2 of Ref. 3. 

The (non-detachable) prefix carba- signifies replacement of a heteroatom by carbon in general natural product nomenclature [26], and may be applied to replacement of the hemiacetal ring oxygen in carbohydrates if there is a desire to stress homomorphic relationships. If the original heteroatom is unnumbered, the new carbon atom is assigned the locant of the non-anomeric adjacent skeletal atom, with suffix a . 

Replacement, e.g., azacyclotridecane. Organic replacement names are formed by denoting heteroatoms that replace skeletal atoms of a hydrocarbon molecular skeleton by organic replacement prefixes (Table 3.4). In nomenclature, the prefixes are cited in the order they are given in the table. 

Substitutive nomenclature is a system in which names are based on the names of parent hydrides, which define a standard population of hydrogen atoms attached to a skeletal structure. Names of derivatives of the parent hydrides are formed by citing prefixes or suffixes appropriate to the substituent groups (or substituents) replacing the hydrogen atoms (preceded by locants when required), joined without a break to the name of the unsubstituted parent hydride. 

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