Chemical Abstracts system

An introduction to using the Chemical Abstracts System can be found in the tutorial in Section 5.5. 

The Chemical Abstracts System (CAS) produces a set of various databases ranging from bibliographic to chemical structure and reaction databases. All the databases originate from the printed media of Chemical Abstracts, which was first published in 1907 and is divided into different topics. Author index, general index, chemical structure index, formula index, and index guide arc entries to the corresponding database (Table 5-3). 

The abbreviations used in the references for titles of journals and periodicals are those used in BP publications practice and conform closely to the recommendations of the Chemical Abstracts system. Abbreviations which have been used to indicate textbook and reference book sources of information are set out below with the full titles and publication details. 

Chemical identity may appear to present a trivial problem, but most chemicals have several names, and subtle differences between isomers (e.g., cis and trans) may be ignored. The most commonly accepted identifiers are the IUPAC name and the Chemical Abstracts System (CAS) number. More recently, methods have been sought of expressing the structure in line notation form so that computer entry of a series of symbols can be used to define a three-dimensional structure. For environmental purposes the SMILES (Simplified Molecular Identification and Line Entry System, Anderson et al. 1987) is favored, but the Wismesser Line Notation is also quite widely used. 

When the two radicals attached to the azo group are derived from different parent molecules, the IUPAC system places the term azo between the complete names of the (substituted) parent molecules (Rule C-911.2). This system resembles an older numbered azo bridge system. The Chemical Abstracts system names the compound as a parent molecule RH substituted by a radical R N=N— (Rule C-912.4). This system is particularly convenient for unsymmetrically substituted aliphatic azo compounds. 

The variety of methods of naming azo compounds which has been in use for many years may lead to considerable confusion, especially when attempts are made to name structural formulas of highly substituted dye molecules with several azo linkages. Furthermore, in regard to the older dye literature, an intuitive interpretation of an author s intention frequently seems more productive than a detailed analysis of the system of nomenclature which he may be using. An effort is made in this chapter to conform to either the IUPAC or the Chemical Abstracts system [la]. 

When the same number and kinds of substituents are carried by the two aromatic radicals, the IUPAC system simply numbers the substituents in a conventional manner, whereas the Chemical Abstracts system names the compound as an assembly of identical units with the prefix azodi- preceding the name of the unsubstituted parent compound ... 

Appendix A lists molecular and fragment formulas in order of the unit masses. Under each unit mass, the formulas are listed in the familiar Chemical Abstract system. The formula mass (FM) to four decimal places is given for each formula. Appendix A is designed for browsing, on the assumption that the student has a unit... 

In the case of tetraxoles we use the Chemical Abstract system of numerarion,... 

The disadvantages of the Stelzner system, as applied to carbocycles, are not very serious. The original system did not indicate how to deal with cases of fusion involving two adjacent bonds in each component, but is capable of logical extension to cover such cases. However, the IUPAC/Chemical Abstracts system is simpler in that it always names the form of the molecule with maximum unsaturation and yields a uniform numbering system for the skeleton it is also more able to deal with complex cases. 

IUPAC/Chemical Abstracts System (IUPAC Rule B-3). The fusion operations described in Section II, A, 3, a are applied to trivial and/or Hantzsch-Widman names of heterocyclic (and, if present, car-bocyclic) components see examples 25-27. In addition a unit consisting of a benzene ring fused to a one-ring heterocycle can be considered as a single component. If this one-ring heterocycle contains 3-10 members it... 

The nomenclature for the chemical species included in this publication does not fully correspond to the current Chemical Abstracts practice. The attempt has been made to use names as easily understandable as possible while not deviating far from the Chemical Abstracts system. Cited are... 

As the number of known chemical compounds neared the million mark, literature about them and less definite substances or products became increasingly difficult to index. Chemical Abstracts and Chemisches Zentralblatt responded with improvements in entry selection and arrangement, and explained their improvements to searchers (5, 7). The German science press of the early 1930 s warmly praised the Zentralblatt s new encyclopedic system, which departs further from the strict alphabetic base than does the Chemical Abstracts system. 

Unfortunately there is, even in English, no generally accepted form of transliteration. In the United States we have the Chemical Abstracts system, the Library of Congress system, the Government Printing Office system, the New York Public Library system, and perhaps others as well. The system used by British Abstracts is similar to, but not absolutely identical to, the one used by Chemical Abstracts. 

Few literature searches can remain within the Chemical Abstracts system of abbreviations for any length of time. Even within the confines of Chemical Abstracts, Beilstein, British Abstracts (which discontinued in 1953), Chemisches Zentralblatt, and the Referativnyi Zhurnal, Khimiya the abbreviation of Justus Liebig s Anruden der Chemie will vary from Ann. to A to Annalen to Liebig s Ann, Chem., or Liebigs Ann. Chem. Other examples could easily be appended. 

Of these, the Chemical Abstracts system appears preferable for these reasons The Board on Geographical Names allows a choice depending on the position of the Russian letter in transliterating letter 1. This is done to reproduce the phone of this letter more accurately, but it also opens the door to ambiguity. The use of y for 2 letters is particularly unfortunate, as 2 is readily confused with 5. 

As with the Chemical Abstracts System, if a substituent is present on the nitrogen, it is designated by the prefix N. 

Using the Chemical Abstracts System to Name Amines... 

Draw a diagram to illustrate your answer to Problem 16.17. Use the Chemical Abstracts system of nomenclature to name each of the following amines ... 

The nomenclature of the penicillins, as with most antibiotics, is complex. The Chemical Abstracts system is definitive and unambiguous, but it is too complex for ordinary use (Fig. 38.12). For example, the chemical name for benzylpenicillin sodium is monosodium (2S,5R,6R)-3,3-dimethyl-7-oxo-6-(2-phenylacetamido)-4-thia-1 -azabicyclo[3.2.0]heptane-2-carboxylate. 

The nomenclature used in this book most closely follows the Chemical Abstracts system of naming organic compounds. This system differs, but only slightly,... 

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