Naming and Indexing of Chemical Substances for Chemical AbstractsTM 2007 Edition A publication of Chemical Abstracts Service Published by the American Chemical Society Naming and Indexing of Chemical Substances for Chemical AbstractsTM A publication of Chemical Abstracts Service Published by the American Chemical Society Copyright © 2008 American Chemical Society All Rights Reserved. Printed in the USA Inquiries concerning editorial content should be sent to: Editorial Office, Chemical Abstracts Service, 2540 Olentangy River Road, P.O. Box 3012, Columbus, Ohio 43210-0012 USA SUBSCRIPTION INFORMATION Questions about CAS products and services should be directed to: United States and Canada: CAS Customer Care Phone: 800-753-4227 (North America) 2540 Olentangy River Road 614-447-3700 (worldwide) P.O. Box 3012 Fax: 614-447-3751 Columbus, Ohio 43210-0012 USA E-mail: [email protected] Japan: JAICI (Japan Association for International Phone: 81-3-5978-3621 Chemical Information) Fax: 81-3-5978-3600 6-25-4 Honkomagome E-mail: [email protected] Bunkyo-ku, Tokyo Japan, 113-0021 Countries not named above: Contact CAS Customer Care, 2540 Olentangy River Road, P.O. Box 3012, Columbus, Ohio 43210-0012 USA; Telephone 614-447-3700; Fax 614-447-3751; E-mail [email protected]. For a list of toll-free numbers from outside North America, visit www.cas.org. 1 Naming and Indexing of Chemical Substances for Chemical Abstracts 2007 ¶ 102 NAMING AND INDEXING OF CHEMICAL SUBSTANCES 101. Foreword. Although the account which follows describes in consid- zwitterions (inner salts, sydnones). The changes for the Fourteenth (1997- erable detail the selection of substance names for Chemical Abstracts (CA) in- 2001) Collective Index period affect coordination nomenclature, stereochemi- dexes, it is not a nomenclature manual. It has the more restricted aim of cal practices, and stereoparents. The most recent changes (2007) involve lo- enabling a user of CA indexes to proceed from the structure of an individual cants, tautomers, and stereoparents. These changes, as well as the changes chemical compound to the place in the current Chemical Substance Index made in 1972, and in the Tenth (1977-1981) and Eleventh (1982-1986) Collec- where the particular index name and any associated index entries will be found. tive Index periods, are reviewed in Section G (¶¶ 225-293). The nomenclature This is the identical operation performed by a CA indexer when assigning an of fullerenes is more fully documented in ¶ 163A of Section B. index name to a new or previously unnamed substance. What follows, in fact, The arrangement of sections is as follows: is a comprehensive summary of CA substance indexing policies, which cover not only conventional organic and inorganic compounds but other completely A. Nomenclature Systems and General Principles (¶¶ 103-139) defined substances entered in the Chemical Substance Index and given CAS B. Molecular Skeletons (¶¶ 140-163A) Registry Number® identifiers. These substances include specific chemical ele- C. Principal Chemical Groups (Suffixes) (¶¶ 164-177) ments, alloys, minerals, mixtures, polymers, enzymes, polysaccharides, and el- D. Compound Classes (¶¶ 178-201) ementary particles. E. Stereochemistry and Stereoparents (¶¶ 202-212) The chemical nomenclature used by Chemical Abstracts Service (CAS) has F. Specialized Substances (¶¶ 213-224) developed in parallel and generally in accordance with the rules published by G. Chemical Substance Names for Retrospective Searches (¶¶ 225- the International Union of Pure and Applied Chemistry (IUPAC). Although 293A) these rules provide unambiguous text equivalents for the great majority of sub- H. Illustrative List of Substituent Prefixes (¶ 294) stances, equally acceptable alternative rules within the present IUPAC system J. Selective Bibliography of Nomenclature of Chemical Substances often lead to two or more unambiguous names. This causes no difficulty in nor- (¶¶ 295-308) mal scientific communication, but is totally unacceptable in a formal, rigidly K. Chemical Prefixes (¶¶ 309-311) controlled, alphabetic listing such as the Chemical Substance Index. Here the L. Chemical Structural Diagrams from CA Index Names (¶¶ 312-318) names must be not only unambiguous, unique, and totally reproducible, but se- M. Index lected so as to bring the names of structurally related substances into juxtapo- sition in the alphabetical listing. They must be equally derivable by index users The arrangement within each of these sections is indicated by a key at the be- searching for information about individual substances and by those who pre- ginning of the section. pare the index. It is also desirable that both should be able to use mechanical In the development of CAS policies for index names of chemical substanc- aids in name generation and retrieval. es, no new nomenclature systems have been devised. Adaptation of current IU- A major revision of CA index names was carried out in 1972 as the Ninth PAC rules to the specific needs of a highly ordered alphabetical index, not Collective Index period began. Most trivial names were dropped; exceptional arbitrary coinage of new terms, has been the approach taken. It continues to be treatment for various classes of substances was discontinued. Where, because recognized by CAS that, while a unique name is needed for an index, and that of the stereochemical complexity of a natural product name, a trivial name was this name, and the CAS Registry Number, are invaluable aids for substance retained as a “stereoparent” (see ¶ 202), diagrams were furnished in the Chem- identification, the use of this invariant index name for citation throughout every ical Substance Index to aid interpretation of index entries. The 1972 nomencla- context in the scientific community is neither practicable nor desirable. But in- ture revision and the reasons for its adoption are set forth in greater detail in the ternational agreement in chemical nomenclature, as embodied in the rules of Ninth Collective Index Guide and in a journal article (J. Chem. Doc. 1974, IUPAC, IUB, and other organizations, continues to be of the greatest impor- 14(1), 3-15). tance in restricting the arbitrary proliferation of substance names. References The preferred CA index names for most chemical substances have been to individual rules which have formed the basis of CAS policies recorded in the continued unchanged since that date. Changes in name-selection policies for sections that follow have not been cited, but the selective bibliography of the the Twelfth (1987-1991) and Thirteenth (1992-1996) Collective Index periods nomenclature of chemical substances which constitutes Section J contains a affect alloys, carbohydrates (lactams), coordination compounds, formazans, comprehensive list of current accepted rules. index name selection (multiplicative names), inorganic compounds (line for- 102. Acknowledgement. CAS acknowledges the large contribution made mulas of clusters, intermetallic compounds), molecular addition compounds by Cecil C. Langham in helping to develop and record CA name-selection pol- (common components; hydrates), nitrilimines, onium compounds (free radi- icies for the Eighth Collective period (1967-1971) during the years immediate- cals), peptides, phosphonium ylides, phosphoryl halides and halogenoids, ly preceding his retirement in 1969. Dr. Langham’s work constituted an polymers (block, graft, and hydrolytic), ring systems (list of common systems), invaluable starting point for the revised name-selection policies introduced in salts (lists of common anions), stereochemistry (sign of optical rotation), and 1972. A. NOMENCLATURE SYSTEMS AND GENERAL PRINCIPLES Introduction ¶ 103 Order of citation of derivative terms ¶ 113 Inversion of names 104 Locants 114 Name selection principles 105 for substituent suffixes 115 Order of precedence of compound classes 106 in substituent prefixes (radicals) 116 Spelling 107 for substituents on parents and parent radicals 117 Punctuation 108 in multiplicative nomenclature 118 Enclosing marks 109 for functional derivatives 119 Multiplicative prefixes 110 for indefinite compounds 120 “Mono” 111 Alphabetization 121 Functional derivatives 112 ¶ 103 Naming and Indexing of Chemical Substances for Chemical Abstracts 2007 2 Tautomeric compounds ¶¶ 122 Substituent suffixes 131 Additive nomenclature 123 Substituent prefixes 132 Conjunctive nomenclature 124 Compound radical names 133 Multiplicative nomenclature 125 Carbonyl radicals 134 Radiocofunctional nomenclature 126 Indicated hydrogen 135 Replacement (“a”) nomenclature 127 Added hydrogen 136 Replacement prefixes 128 Numbering of molecular skeletons 137 Replacement nomenclature for functions 129 Index name selection 138 Substitutive nomenclature 130 Subtractive nomenclature 139 103. Introduction. Many names may be employed in scientific publica- (i) Aldehydes, Thials, Selenals, Tellurals. tions for a single compound. Even so simple a compound as H2NCH2CH2OH (j) Ketones, Thiones, Selones, Tellones. can be named 2-Aminoethanol, 2-Aminoethyl alcohol, 2-Hydroxyethylamine, (k) Alcohols and Phenols (of equal rank), Thiols, Selenols, Tellurols. β-Hydroxyethylamine, 2-Hydroxyethanamine, 1-Amino-2-hydroxyethane etc., (l) Hydroperoxides. all of which describe it unambiguously; often, the less systematic (“trivial”) (m) Amines. name Ethanolamine may be encountered. For more complex compounds, the (n) Imines. (This is the lowest compound class expressed by a functional number of possible names increases exponentially. suffix; all the following