Chemical Abstracts indexing system

The rules of the I.U.C. (Definitive Report of the Commission on the Reform of the Nomenclature of Organic Chemistry ) and the Chemical Abstracts indexing system are followed for the most part, with adaptation to meet the needs of situations encountered in certain coordination compounds. For example, OCH2CH2OCH2CH2 is called... 

Quite naturally there is a certain amount of arbitrariness in this system, although the lUPAC nomenclature is followed. The preferred Chemical Abstracts index names for chemical substances have been, with very few exceptions, continued unchanged (since 1972) as set forth in the Ninth Collective Index Guide and in a journal article. Any revisions appear in the updated Index Guide new editions appear at 18-month intervals. Appendix VI is of particular interest to chemists. Reprints of the Appendix may be purchased from Chemical Abstracts Service, Marketing Division, P.O. Box 3012, Columbus, Ohio 43210. 

The systematic nomenclature used originally the term imidazo-1,2,3-triazine. The Chemical Abstracts indexes use the more accurate name imidazo[4,5-d]-Z -triazine (141). The numbering of the substituents is different in the two systems of nomenclature as may be seen in the formulas. 

According to the systematic nomenclature these substances were first named l-f-triazolo[d] pyrimidines in compliance with the general principles of the Ring Index/ More recent papers and Chemical Abstracts indexes use the term i -triazolo[4,5-d]pyrimidine (147) in accord with the lUPAC nomenclature. The numbering of substituents when using the last-mentioned name is different from that of the 8-aza analogs. For the formulas of oxygen and sulfur derivatives names derived from the lactim or thiolactim form are almost exclusively in use (in common with the purine derivatives). These derivatives are thus described as hydroxy and mercapto derivatives, respectively. The name 1,2,3,4,6-pentaazaindene is used only rarely for this system. 

Common names of the compounds arc used throughout this volume. Preparations appear in the alphabetical order of common names of the compound or names of the synthetic procedures. The Chemical Abstracts indexing name for each title compound, if it differs from the common name, is given as a subtitle. Because of the major shift to new systematic nomenclature adopted by Chemical Abstracts in 1972, many common names used in the text are immediately followed by the bracketed, new names. Whenever two names are concurrently in use, the correct Chemical Abstracts name is adopted. The prefix n- is deleted from w-alkanes and w-alkyls. In the case of amines, both the common and systematic names are used, depending on which one the Editor-in-Chief feels is more appropriate. All reported dimensions are now expressed in Systeme International units. 

Although all alkaloids can be named by the principles already outlined in this article, the cumbersome nature of such names for complex ring systems makes it desirable to use trivial parent names for some large heterocyclic skeletons. It is preferable for such trivial names to refer to skeletons with no substituents (or very few), and it is often convenient for them to carry inherent stereochemical implications. The most extensive source of these names is the Chemical Abstracts Index Guide (or the Ninth Collective Index Nomenclature Manual), but the names given here do not correspond, in many cases, to those in common use, and IUPAC recommendations, when they appear, may well differ in some respects. Some of the principal skeletons listed by Chemical Abstracts are illustrated (122-130). 

In a second generation of MEDLARS, which is planned for implementation this fall, it will be possible, with the aid of the data base established through the Chemical Abstracts registry system, to index biomedical publications with many more specific terms and chemicals than has been possible under MEDLARS I. While it is not projected that this extensive listing of chemical compounds be included in Index Medicus, it will be possible to provide such listings in other MEDLARS products. Thus a current publication of the Library, the Toxicology Bibliography, will list the biomedical literature by any desired chemical classification. 

This nucleus has also been referred to as 4,5-quinoxalinoimidazole and imidazolo-5, 4 2,3-quinoxaline. Most of the reported derivatives of this ring system are cyanine dyestuffs and may be named accordingly. For example, Chemical Abstracts indexes compound SO as an imidazo[4,5-h]quinoxalinocarbocyanine, as well as by using more systematic nomenclature. Similarly 51 may also be called an imidazo[4,5-h]quinoxalino-indocarbocyanine, and compound 52 is referred to as an imidazo[4,5-b ]quinoxalinothiacarbocyanine. 

This chapter summarizes the syntheses of various tetracyclic and pentacyclic condensed thiophene systems that are reported in Chemical Abstracts, Index of Ring Systems for the period from 1952 through December 31, 1980 (i.e., through Volume 93). Previous syntheses are reported in the monograph... 

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