CAS Registry System

Registry File. This CAS file contains more than 11.8 million chemical substance records. About 8,000—14,000 records are added each week as new substances are identified by the CAS Registry System. The substance records contain CAS Registry Numbers, chemical names, stmctures, molecular formulas, ring data biosequence information, and classes for polymers. AH of this information may be displayed. 

Chemical Abstracts and GAS Registry. CAS is especially notable for the thoroughness and high quaUty of its products. The CAS Registry system does a superb job of identifying any chemical that is either involved in new chemistry with hard data, or, since about 1980, specifically claimed in a patent. The MARPAT database has also led CAS to identify the perhaps nonexistent but prophetic substances covered by Markush claims in patents. 

CAS Registry Number (CASRN) This unique identifier is assigned by the American Chemical Society to chemicals recorded in the CAS Registry System. This number is used to access various chemical databases including the Hazardous Substances Data Bank (HSDB), CAS Online, Chemical Substances Information Network, and many others. This entry is also useful to conclusively identify a substance regardless of the assigned name. 

Note The formulas in the Inorganic Syntheses, VoL 32 Formula Index fallow the CAS Registry system. 

Chemical structure files must be planned to cope with large numbers of compounds. The total number of unique compounds known has been estimated to be between 4 and 5 million, and the number of compounds in the CAS Registry System is now over 2 million. Great efforts must therefore be made to compress the files as much as possible. Thus, in the CAS and other topographical systems only non-hydrogen atoms and their connections are considered. The computer knows the normal valence of every atom. Connections to non-hydrogen atoms are specified and all unfilled valencies are assumed to be to hydrogen. 

The KWIC indexing philosophy has also been successfully applied to chemical notations, in particular the Wiswesser Line Notation. The ease with which computers can handle numbers has also been exploited in handling structural data. In the various structural registries, notably the CAS Registry System 53,54) each compound is assigned a unique number which can then be used as the label for the compound rather than the full structural record. 

Eastman Kodak has many laboratories worldwide, all with their own information departments, but the Information and Computer Technology Division in Rochester, and in particular the Application and Data Resources Unit, is responsible for the 555,000 compounds in the Chemical Registry System (under both MACCS and CAS Registry System software). There are also on file 17000 reactions under REACCS, 190,000 reports and 65,000 patents in a photographic patents index. The Chemical Information Centre holds 1,100,000 index cards, half of them in accession number order and half in molecular formula sequence. 

Chemical Abstracts Service (CAS) since 1967 has represented pol3oners in the CAS Registry System, and provided corresponding CA Index names , in two ways ... 

In order to use this method in the CAS Registry System, we extended it to cover cases where stereochemistry is only partially known, such as the substance of... 

Du Pont s topology input procedure is an adaptation of the Registry system developed by CAS from work done initially by Du Pont. This work was shared with CAS and the American Chemical Society with the expectation that they would use it to benefit the chemical community. The CAS Registry System and Du Pont s chemical system are based on a chemical structure storage and search system co-operatively developed by both organisations. 

The initial system. Registry I, which began operation in I 1964, established the viability and validity of the registration concept for fully defined organic substances. In 1968, the second version of the CAS Registry System, Registry II, was established. The scope of the system was increased to include inorganic substances, coordination compounds, polymers, mixtures, alloys, and incompletely defined substances. 

Although the stereochemical descriptor was effective for the CAS Registry System, it was not amenable to computer manipulation necessary to support features such as stereo display and stereo structure search. In order to improve stereochemical features, CAS has converted about 90% of the stereochemical descriptors to an atom/bond-specific representation in the connection table (Figure 13). 

The CAS Registry System contains not only the Registry File for structural data, but also the Nomenclature File, containing CA index names and synonyms, which may be other systematic names, common names, trade names, etc. (see Nomenclature Searching and Nomenclature Automatic Generation and Conversion) Currency, there are over 24 million chemical names in the Registry System. 

Other names, for example, semisystematic, common, or trade names may appear. Whether a substance record contains one of these names depends on whether such a name was input to the CAS Registry System by CAS document analysts when preparing CA Chemical Substance Index entries. 

In the past few years, improvements have been made to the CAS Registry System in the areas of alloys, inorganic compounds, 3D structures, biosequences, polymers, and manually registered substances, in addition to the changes in handling of stereochemistry, previously described. 

When the polymer structure is well documented by the author or can be confidently assumed, because one and only one structure is chemically possible, then a supplementary representation with a corresponding systematic name is added to the CAS Registry System and included in the printed indexes and online files. 

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