Functional replacement nomenclature

This occurs when one or more oxygen atoms in a functional group are notionally replaced by other heteroatoms. Depending on the hierarchy, this may lead to the use of functional replacement prefixes (e.g., seleno in selenoacetic acid, H3C-C(=Se)OH), infixes, or suffixes (e.g., in benzenecar-bodithioic acid, Ph-C(=S)-SH). 

Because of the large number of possible functional groups thus generated, lUPAC guidance is incomplete, and there is also considerable duplication of possible names, e.g., -CH=Se is selenofor-myl or selenoxomethyl. Table 3.6 gives a list of common replacement suffixes. 

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Parent Acid Names Used in Functional Replacement Nomenclature of Phosphorus and Arsenic Compounds... 

The name in Example 4 regards the compound as derived from arsonic acid, by substitution of a phenyl group for the hydrogen atom bound directly to arsenic. The name in Example 5, in addition to the hydrogen substitution, involves functional replacement nomenclature (Section IR-8.6). 

Several names omitted from Ref. 2, e.g. selenic acid and hypobromous acid, are reinstated because they are unambiguous and remain in common use (including their use as parent names in functional replacement nomenclature, see Section IR-8.6). 

Terminal vowel of infixes used in functional replacement nomenclature (Section IR-8.6) to indicate replacement of oxygen atoms and/or hydroxy groups, e.g. amido , nitrido , thio . 

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. 

Current IUPAC and Chemical Abstracts nomenclature has been employed in this index with the former given preference. Substitutive nomenclature has been given preference over radicofunc-tional, additive, subtractive, conjunctive or replacement nomenclature, except where this becomes unwieldy. With many bicyclic and polycyclic compounds bearing heteroatoms, standard bicyclic or polycyclic oxa, aza, and thia replacement nomenclature has often been used. With certain functional groups, where the names are rather complex and probably not familiar to most organic chemists, such as ylides, those compounds have simply been named as sulfur, tellurium and arsonic ylides. Metal catbenes have been treated similarly. With more complex functionality and many heterocycles, the Beilstein Commander Crossfire nomenclature system has been used with certain modifications. 

Replacement nomenclature emphasizes the length of the repeat unit but masks the functionality (i.e., amide) in these units. Alternatively, a repeat unit name (such as, (propanamido)methylidyne), which indicates the functionality but obscures the chain length, may be preferred. The style chosen for the internal (or core or terminal) unit name(s) does not affect the general form of the proposed cascade nomenclature. Thus, the cascade in Figure 3.5 is 36-Cascade tricyclo[3.3.l.l3,7]decane[4-l,3,5,7] (3-oxo-2-aza-propylidyne) (3-oxo-2-azapentylidyne) propanoic acid. 

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. 

Functional replacement names may, of course, be used for the derived parent acids themselves. However, this amounts to introducing an additional system which is not needed in inorganic nomenclature. As mentioned above, additive and substitutive nomenclature can... 

The term "heteroatom" applies to any atom other than carbon or hydrogen. It is common for heteroatoms to appear in locations that are inconvenient to name following basic rules, so a simple system called "replacement nomenclature" has been devised. The fundamental principle is to name a compound as if it contained only carbons in the skeleton, plus any functional groups or substituents, and then indicate which carbons are "replaced" by heteroatoms. The prefixes used to indicate these substitions are listed here in decreasing priority and listed in this order in the name ... 

Substitution means the replacement of one or more hydrogen atoms in a given compound by some other kind of atom or group of atoms, functional or nonfunctional. In substitutive nomenclature, each substituent is cited as either a prefix or a suffix to the name of the parent (or substituting radical) to which it is attached the latter is denoted the parent compound (or parent group if a radical). 

Similarly, with exocyclic O-PACs, substitutive nomenclature and common suffixes are used to describe the O-atom compounds formed when an H-atom on a PAH is replaced by another atom or functional group, e.g., 6-hydroxybenzo[ ]pyrene, XIX, or 2-methoxychrysene, XX ... 

The lUPAC nomenclature of alkynes is similar to that for alkenes, except the -ane ending is replaced with -yne. The chain is numbered from the end closest to the triple bond. When additional functional groups are present, the suffixes are combined. 

Hydrocarbons, esters, etc., which have one or more hydrogen atoms replaced by a halogen atom are named so that the substituents have the lowest possible numbers. When multiple functions are present, they are numbered according to precedences established by IUPAC or CAS nomenclature rules. Both trivial and systematic nomenclatures are used. 

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