Polynuclear nomenclature

The fuel oils coming out of olefin plants are also characterized by an abundance of polynuclear aromatic molecules, (Same definition as for Figure 2—1). They are sometimes inaccurately referred to as having a high aromatics content. Nomenclature aside, because of this, the burning characteristics of pyrolysis gas oil and pyrolysis pitch are poor. They are smoky, sooty, and gum formers they rend to be more viscous, and because of their polynuclear aromatic concent, they are suspected carcinogens. They are basically a witchs brew of unsavory hydrocarbons.. ... 

The nomenclature used in this book is presented in section 3.1. It should be noted [2] that For polynuclear complexes and complexes with several kinds of ligands, it may sometimes be practicable to use P with... multiple subscripts. Their general meaning must then be defined very clearly with a full... 

The names of unsaturated compounds are derived by using appropriate substitutive nomenclature rules. Note that trivial names are also allowed for particular polynuclear species, for example, N2H4, diazane, commonly known as hydrazine. For a discussion of names of hydrides in which elements exhibit non-standard bonding numbers, see the Nomenclature of Inorganic Chemistry, p. 85. Note that for the hydrides of Table 5.1 and their derivatives, substitutive names are generally preferred. 

We follow the 1979 IUPAC recommendations summarized in Polynuclear Aromatic Hydrocarbons Nomenclature Guide (Loening et al. 1990). The American Chemical Society also publishes the Ring Systems Handbook, which, ca. 1990, contained structural diagrams for over 70,000 unique ring systems (American Chemical Society, 1977 to present). 

Later, D. W., C. W. Wright, K. L. Loening, and J. E. Merritt, Systematic Nomenclature of the Nitrogen, Oxygen, and Sulfur Functional Polycyclic Aromatic Compounds, in Polynuclear Aromatic Hydrocarbons Nomenclature Guide (K. Loening, J. Merritt, D. Later, and W. Wright, Eds.), pp. 27-47, Battelle Press, Columbus, OH, 1990. 

Loening, K., J. Merritt, D. Later, and W. Wright, Polynuclear Aromatic Hydrocarbons Nomenclature Guide, 1st ed., Battelle Press, Columbus, OH, 1990. 

Tins nomenclature extends to still more complicated structures where central atoms are added together to form dinuclear, innuclear. and even polynuclear species from some mononuclear building blocks. The persistent centrality of the central atom is emphasized by the root -nuclear. 

Polynuclear inorganic compounds exist in a bewildering array of structural types, such as ionic solids, molecular polymers, extended assemblies of oxounions both of metals and nonmeinis, nonmetal chains and rings, bridged melui complexes, and homo- and hetero-nuclcar clusters. This section treats primarily the nomenclature of bridged metal complexes and homo- and hetero-nuclear dusters. 

This chapter presents a concise overview of the present conventions in coordination nomenclature. Generally, the IUPAC rules and recommendations have been followed. For the cases where the IUPAC practices seemed to be out of date or incomplete, the author has drawn upon the vast expertise in nomenclature available at Chemical Abstracts Service. Sections 3.2.3 and 3.4 deal with ligand locant notation and the numbering of polynuclear complexes may be considered provisional. These concepts are still under active consideration in the various national and international nomenclature commissions and committees. The presentation is relatively brief, but it is hoped that the nomenclature principles are evident, especially when examples presented are closely... 

Polynuclear compounds may be either of such large extended structures as to make rational structure-based nomenclature impractical, or the structures may be undefined or partially elucidated. In these instances compositional nomenclature is most suited. 

Structural nomenclature for more complex polynuclear compounds is based on the description of the fundamental structural unit, and a logical procedure for numbering the atoms of the fundamental or central structural unit. For nonlinear clusters, descriptors such as tetrahedro, dodecahedro, etc. have traditionally been used to describe a central structural unit (CSU). However, synthetic chemistry has now advanced far beyond the utility of the limited CSU set associated... 

The present discussion of isomerism in coordination compounds is not, nor was it intended to be, comprehensive and exhaustive. The examples considered are an eclectic selection, and many important systems may have been neglected through ignorance. An obvious omission is any detailed consideration of polynuclear complexes139,256"259 and it is, of course, a quite arbitrary decision not to include any consideration of organometallic species. Other neglected issues, such as the development of a truly comprehensive system of stereochemical nomenclature, are perhaps not yet capable of solution. Nevertheless, it is to be hoped that the principal factors to be considered... 

Polynuclear Aromatic Hydrocarbons 735 16-11 Aromatic Allotropes of Carbon 737 16-12 Fused Heterocyclic Compounds 739 16-13 Nomenclature of Benzene Derivatives 740... 

Details about formulae and names of polynuclear complexes can be found in Nomenclature of Inorganic Chemistry, It need only be mentioned here that a bridging group is indicated in the formula by separating it from the rest of the complex by hyphens, and in the name by prefixing it with ... 

IR-1.5.3.2 Compositional nomenclature IR-1.5.3.3 Substitutive nomenclature IR-1.5.3.4 Additive nomenclature IR-1.5.3.5 General naming procedures IR-1.6 Changes to previous IUPAC recommendations IR-1.6.1 Names of cations IR-1.6.2 Names of anions IR-1.6.3 The element sequence of Table VI IR-1.6.4 Names of anionic ligands in (formal) coordination entities IR-1.6.5 Formulae for (formal) coordination entities IR-1.6.6 Additive names of polynuclear entities IR-1.6.7 Names of inorganic acids IR-1.6.8 Addition compounds IR-1.6.9 Miscellaneous... 

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. 

Substitutive nomenclature is recommended only for derivatives of the parent hydrides named in Table IR-6.1 (in Section IR-6.2.1), and derivatives of polynuclear hydrides containing only these elements (see Sections IR-6.2.2 to IR-6.2.4). The bonding numbers of the skeletal atoms are understood to be as in Table IR-6.1 (these bonding numbers, e.g. 4 for Si and 2 for Se, are termed standard bonding numbers). Other bonding numbers must be indicated by an appropriate designator (the X convention , see Section IR-6.2.2.2 and Section P-14.1 of Ref. 1). 

This nomenclature then extends to more complicated structures where central atoms (and their ligands) are added together to form polynuclear species from mononuclear building blocks. Complicated structures are usually more easily named by treating them as polynuclear species (see Section IR-9.2.5). 

As a general principle, as much structural information as possible should be presented when writing the formula or name of a polynuclear complex. However, polynuclear complexes may have structures so large and extended as to make a rational structure-based nomenclature impractical. Furthermore, their structures may be undefined or not suitably elucidated. In such cases, the principal function of the name or formula is to convey the stoichiometric proportions of the various moieties present. 

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