Chemical Abstracts Service complexes

When compounds of complex structure are considered, the number of name possibilities grows rapidly. To avoid having index entries for all possible names. Chemical Abstracts Service has developed what might be called the principle of inversion. The indexing system employs inverted... 

With more than 30 million organic compounds now known and thousands more being created daily, naming them all is a real problem. Part of the problem is due to the sheer complexity of organic structures, but part is also due to the fact that chemical names have more than one purpose. For Chemical Abstracts Service (CAS), which catalogs and indexes the worldwide chemical literature, each compound must have only one correct name. It would be chaos if half the entries for CH3B1 were indexed under "M" for methyl bromide and half under "B" for bromomethane. Furthermore, a CAS name must be strictly systematic so that it can be assigned and interpreted by computers common names are not allowed. 

Even the development of Mendeleyev s periodic table of chemical elements did not grant researchers the ability to plan and design new materials. Although Mendeleyev correctly predicted the existence of a few new elements, the number of compounds that can be made from elements is extremely vast and complex. Chemical Abstracts Service, a division of the American Chemical Society, maintains a registry of known substances. As of May 2009, there are about 47 million substances in this registry, and roughly 4,000 new substances are added every day. 

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 For the cases where the IUPAC practices seemed to be out of date or incomplete, the author has drawn upon the vast expertise in nomenclature available at Chemical Abstracts Service.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... 

Now, returning to the structure of the cobalt complex, we have derived the rankings as shown in Figure 7. One might agree that these are highly stylized and schematic procedures and the formalism leads to some results not intuitively anticipated. However, at Chemical Abstracts Service, we have accumulated a vast amount of experience with the CIP system with hundreds of thousands of compounds, both organic and coordination, and we find very few cases in which the CIP formalism completely breaks down. 

The numbers provided by the Chemical Abstracts Service (CAS) [4] are the unanimously accepted definitions for chemical substances. Given the complexity of this class of substances, an exhaustive listing of CAS numbers is not possible. Nevertheless, the following information contained in Table 1 provides a partial list of CAS numbers that contain chlorinated alkanes that fall within the defined range of SCCPs. 

Today Chemical Abstracts Service (CAS) has no structure conventions applied to transition metal complexes which separate a- from iT-bonding interaction between metal atoms and ligands. Even the projected GMELIN-ONLINE will treat all metal to ligand connectivities as ordinary covalent bonds. 

Because of the wide variety of features in complex molecules, naming them is more an art than a science. While both the family names mentioned above have historic roots, it would be useful to consider more rational names for new, but closely related, families based on their stmcture. To avoid addressing this problem directly, the tradename Rhodonine will be used in this work to describe the chromophores of biological vision. The specific systematic names assigned to this family by the Registry Services division of Chemical Abstracts are given below and in the appendices. 

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