Changes in CAS Nomenclature

CAS nomenclature was stable for most organics between 1977 and 2006 and the system was known as 9CI nomenclature. 

The following specialised classes of organic substances or types of names were subject to changes during the twelfth (1987-1991) or thirteenth (1992-1996) Collective Index periods  

Organic Chemist s Desk Reference, Second Edition 

Further major changes to CAS nomenclature affecting organics were made in 2006 and are described at www.cas.org. 

Some examples of the 2006 changes affecting simple mainstream organics are shown here. Other changes affecting more specialised areas of nomenclature are referred to in the following chapter. 

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Major changes in CAS nomenclature were made at the beginning of the ninth Collective Index period (1972), giving what became widely known as 9C1 nomenclature. This is described in the publication Naming and Indexing of Chemical Substances for Chemical Abstracts (Appendix IV to the CAS 1992 Index Guide, but also available separately). 

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