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The systematic lUPAC nomenclature of compounds tries to characterize compounds by a unique name. The names are quite often not as compact as the trivial names, which are short and simple to memorize. In fact, the lUPAC name can be quite long and cumbersome. This is one reason why trivial names are still heavily used today. The basic aim of the lUPAC nomenclature is to describe particular parts of the structure (fi agments) in a systematic manner, with special expressions from a vocabulary of terms. Therefore, the systematic nomenclature can be, and is, used in database systems such as the Chemical Abstracts Service (see Section 5.4) as index for chemical structures. However, this notation does not directly allow the extraction of additional information about the molecule, such as bond orders or molecular weight. 

The WLN was applied to indexing the Chemical Structure Index (CSI) at the Institute for Scientific Information (ISI) [13] and the Ituiex Chemicus Registry System (ICRS) as well as the Crossbow System of Imperial Chemical Industries (ICl). With the introduction of connection tables in the Chemical Abstracts Service (CAS) in 1965 and the advent of molecular editors in the 1970s, which directly produced connection tables, the WLN lost its importance. 

More than 10 000 databases exist that provide a small or large amount of data on various topics (including chemistry). The contents in databases are supplied by approximately 3500 database developers (e.g., the Chemical Abstracts Service, MDL Information Systems, etc.). Since there is a variety of topics from economics to science, as well as a variety of structures of the database, only some of the vendors (-2000) offer one or more databases as either local or as online databases (Figure 5-4) [4]. Usually, databases are provided by hosts that permit direct access to more than one database. The search occurs primarily through different individual soft-... 

The lUPAC rules are not the only nomenclature system in use today Chemical Abstracts Service sur veys all the worlds leading scientific journals that publish papers relating to chemistry and publishes brief abstracts of those papers The publication Chemical Abstracts and its indexes are absolutely es sential to the practice of chemistry For many years Chemical Abstracts nomenclature was very similar to lUPAC nomenclature but the tremendous explosion of chemical knowledge has required Chemical Abstracts to modify Its nomenclature so that its indexes are better adapted to computerized searching This means that whenever feasible a compound has a sin gle Chemical Abstracts name Unfortunately this Chemical Abstracts name may be different from any of the several lUPAC names In general it is easier to make the mental connection between a chemical structure and its lUPAC name than its Chemical Abstracts name... 

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... 

The nomenclature of boron hydride derivatives has been somewhat confusing and many inconsistencies exist in the literature. The structures of some reported boron hydride clusters are so complicated that only a structural drawing or graph, often accompanied by explanatory text, is used to describe them. Traditional nomenclature systems often can be used to describe compounds unambiguously, but the resulting descriptions may be so long and unwieldy that they are of litde use. The IUPAC (7) and the Chemical Abstract Service (8) have made recommendations, and nomenclature methods have now been developed that can adequately handle nearly all clusters compounds however, these methods have yet to be widely adopted. For the most part, nomenclature used in the original literature is retained herein. 

J. B. Casey, W. J. Evans, W. H. PoweU, and T. E. Sloan, "A Structural Definitive Descriptor and Numbering System for Cluster Compound Nomenclature," Chemical Abstract Service, presented at the 198th National Meeting of the American Chemical Society, Miami Beach, FI., Sept. 1989. 

Zamora, Antonio, and David L. Dayton, "The Chemical Abstracts Service Chemical Registry System. V. Structure Input and Editing," to be published in the August 1976 issue of Journal of Chemical Information and Computer Sciences. 

Walker data set — Walker et al., developed a database that contains a large and diverse collection of known pesticides and industrial chemicals, as well as some food additives and drugs (Walker et al., 2003). The database contains 92,964 Chemical Abstract Service (CAS) Registry numbers of chemicals that will probably have to be evaluated for their potential endocrine disruption. A final data set of 58,391 chemicals was processed by our system after eliminating those chemicals for which structures were not available (Walker et al., 2003) and/or 3D structures could not be generated (Hong et al., 2002). 

Devillers et al. (1996) have commented that most QSARs for the prediction of BCF perform similarly up to log Kow 6. In view of the fact that the computer program BCFWIN version 2.14 is freely available from the EPA website (www.epa.gov/oppt/exposure/docs/episuitedl.htm), it is recommended that this be used for BCF prediction for chemicals with log < 6 the proviso is that highly reactive chemicals will probably have a higher than predicted BCF, perhaps by up to two orders of magnitude. BCFWIN requires that the chemical structure be input using Simplified Molecular Line Entry System (SMILES) notation (Weininger, 1988) or as a Chemical Abstracts Service (CAS) number. 

Registry Number, which is unique to each compound, is used to link the structure with names, references, and other information within the Chemical Abstracts Service Registry Number System. However, there is no way to generate a Registry Number from a given structure, and data on specific compounds can only be recovered by finding the Registry Number first. The first formula index to use these numbers will be that for vol. 71 (1969). 

CAS = Chemical Abstracts Services DOT/UN/NA/IMCO = Department of Transportation/United Nations/North America/International Maritime Dangerous Goods Code EPA = Environmental Protection Agency HSDB = Hazardous Substances Data Bank NCI = National Cancer Institute NIOSH = National Institute for Occupational Safety and Health OHM/TADS = Oi1 and Hazardous Materials/Technical Assistance Data System RTECS = Registry of Toxic Effects of Chemicals Substances SANSS = Structure and Nomenclature Search System... 

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. 

Under its contract with the Chemical Information Program, the Chemical Abstracts Service was to put into the registry system all the compounds indexed in Chemical Abstracts for 1965 and 1966. This amounted to between 450,000 and 500,000 structures entered during the first year of the contract, plus another 400,000 during the second. The system was designed to eventually hold all 3 million compounds known at the time, as well as an estimated 75,000 new compounds per year. Additionally, the system was to include an estimated 15 to 20 million references in publications." With such a vast number of structures to be dealt with, the benefits of a computer system must have been clear. 

CAS ONLINE is Chemical Abstracts Service s computerized system that provides access to substance information from the CAS registry file. CAS ONLINE allows users to search for substances on the basis of structural units, registry number, chemical name, or molecular formula. Portions of the CAS information base are licensed by several information vendors. 

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