The Chemical Abstracts Service (CAS) Chemical Regis-to chemical-compound information through structural ditry System is a computer-based system that uniquely agrams displayed in printed publications until The Ring identifies chemical substances on the basis of their mo-Index (Patterson & Capell, 1940) provided a systematic lecular structures. This article describes the history, arrangement of ring systems and their structures along scope, and applications of the CAS Registry System. Bewith references to the original literature.
gun originally in 1965 to support indexing for Chemical Abstracts, the Registry System now serves not only as One of the earliest means for representing chemical a support system for identifying substances within CAS structures in chemical substance compilations was nooperations, but also as an international resource for menclature. Nomenclature of chemical compounds has chemical substance identification for scientists, indushad a long history beginning with the milestone internatry, and regulatory bodies. The CAS Registry File is the largest file of substance information in the world, con-tional Geneva Conference in 1892 on the standardization taining structures and names for more than 15 million of names that grew out of a series of international meetsubstances. It has become the worldwide authority for ings, the first of which was organized by Kekule in 1860. chemical substance identification information.
Since 1921, the International Union of Pure and Applied Chemistry (IUPAC) has had committees on chemical nomenclature to formulate rules for naming chemical com-