Functional compounds substitutive nomenclature

Section 16 1 Ethers are compounds that contain a C—O—C linkage In substitutive lUPAC nomenclature they are named as al/coxy derivatives of alkanes In functional class lUPAC nomenclature we name each alkyl group as a separate word (m alphabetical order) followed by the word ether... 

Substitutive Nomenclature. The first step is to determine the kind of characteristic (functional) group for use as the principal group of the parent compound. A characteristic group is a recognized combination of atoms that confers characteristic chemical properties on the molecule in which it occurs. Carbon-to-carbon unsaturation and heteroatoms in rings are considered nonfunctional for nomenclature purposes. 

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). 

Systematic names formed by applying the principles of substitutive nomenclature are single words except for compounds named as acids. First one selects the parent compound, and thus the suffix, from the characteristic group listed earliest in Table 1.7. All remaining functional groups are handled as prefixes that precede, in alphabetical order, the parent name. Two examples may be helpful ... 

In order of decreasing priority for citation of a functional class name, and the prefix for substitutive nomenclature, are the following related compounds ... 

The general trend in substitutive nomenclature is to use fewer trivial or retained names and to approach substitutive nomenclature more systematically. A total of 209 trivial names are to be retained 81 for parent hydrides and 58 (those in Chapter 4, Section 4.5.7, p. 91) for functional parent hydrides. These are so well anchored in nomenclature that they will probably survive for a great many years. Finally, 70 trivial names, such as isobutane and neopentane, are still allowed to be specific for non-substituted compounds. Presumably some of these will be discarded during later revisions of the Nomenclature of Organic Chemistry. 

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 ... 

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. 

Radicofunctional Nomenclature. The procedures of radicofunctional nomenclature are identical with those of substitutive nomenclature except that suffixes are never used. Instead, the functional class name (Table 1.9) of the compound is expressed as one word and the remainder of the molecule as another that precedes the class name. When the functional class name refers to a characteristic group that is bivalent, the two radicals attached to it are each named, and when different, they are written as separate words arranged in alphabetical order. When a compound contains more than one kind of group listed in Table 1.9, that kind is cited as the functional group or class name that occurs higher in the table, all others being expressed as prefixes. 

The designation of central atom and ligands, generally straightforward in mononuclear complexes, is more difficult in polynuclear compounds where there are several central atoms in the compound to be named, e.g. in polynuclear coordination compounds, and chain and ring compounds. In each case, a priority order or hierarchy has to be established. A hierarchy of functional groups is an established feature of substitutive nomenclature Table VI shows an element sequence used in compositional and additive nomenclature. 

Since the lUPAC nomenclature system relies totally on the pivotal concept of the parent structure to which, in a second sphere, substituents are assigned, it appeared advisable to maintain this division also for the chapters of this book. Thus, we begin with the exposition of the nomenclature rules for parent structures and, in the second chapter, proceed with the discussion of the different types of nomenclature for substituted systems, radicals, and ions in the third chapter specific classes of functional compounds are addressed, followed, in the forth chapter, by the treatment of metal organyls and, in the fifth, of carbohydrates. The concluding sixth chapter takes up once again the construction of the final names of complex compounds including isotopic modifiers and stereochemical descriptors. 

It is possible to regard radicofunctional nomenclature, in which the functional class narrie of a compound (c.g. alcohol, ketone, etc.) is cited after the names of the attached radicals, as involving an additive procedure (example 146). This type of nomenclature is gradually falling out of use in favor of the substitutive equivalent [for 146 the substitutive name would be l-(3-pyridyl)propan-l-one]. 

The term enamine is used mainly for classifications of the functional group as an ensemble, but individual compounds are termed with respect to the parent compound usually as amino substituted olefins, i.e. tertiary enamines as (N,iV-dialkylamino)alkenes. The correct IUPAC nomenclature for tertiary enamines is dialkylalkenylamines, i.e. the basic compound in this case is the amine not the alkene. The difference may be demonstrated for two examples 73 is in the first notation l-iV-methylanilino-2-methyl-propene and, in IUPAC notation, iV-methyl-jV-(2-methyl-l-propenyl)aniline. Correspondingly 74 is usually called 2-methyl- 1-pyrrolidinopropene but in IUPAC notation it is jV-(2-methyl-l-propenyl)pyrrolidine. 

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