The Structure CAS Databases

Not every substance in the Registry File corresponds to a CA or another literature abstract. In 1983, for one million CAS Registry Numbers there were no literature references. The following groups of substances are stored without a citation in the literature  

By means of this CAS Registry File it is possible to ascertain whether or not a substance with a certain name has already been mentioned under another name. In the course of registration for Chemical Abstracts about 6000 substances are checked daily. If not yet registered, the structural formula of the new substance is first stored. The substance is then awarded a systematic CA Index Name based on lUPAC rules, and the rules of the Chemical Abstracts Service, by a nomenclature expert (Sect. 2.1.3.2). Weekly about 13,000 structures are registered, 690,000 new substances each year (1992). 

Alongside this CAS Registry database which is accessible for online searches (Sects. 7.1, 7.2 and 8) CAS has created other databases containing structural information  

For the Markush structure shown in Fig. 2 the following conditions are defined Rl = Alkyl with Rl substituents in ring position 2, 3 or 4 R2 = NHR with the restriction for R = hydrogen or alkyl compounds with 1 to 3 carbon atoms. The following substance is included in the above mentioned diagram  

MARPAT contains up till now, in addition to the Registry database, 200,000 Markush structures. The CA abstract number and therefore the reference to the patent is mentioned with each structure. MARPAT is one of the only two information sources worldwide, which allow structure searching only in patents and ascertain the most obscure substance which could be concealed in a Markush structure. Without the support of computer programs the systematic interpretation of Markush structures would often be impossible. The second database, which offers similar possibilities, is Markush DARC (Sect. 7.8). 

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