 |
|
Ask REGgie: New CA index name rules in 2007
Q. I noticed that new substances in REGISTRY do not have the (9CI) label on the CA index name. Why is this, and have the rules for assigning CA index names changed? A. CAS is implementing the first major rule changes for CAS index names since 9CI rules were adopted in 1972. In December 2006, CAS began the transition from 9CI (9th Collective Index) index nomenclature rules to new CA index nomenclature rules. CAS no longer categorizes information by collective index periods, so the new CA index names will no longer have a CI label. The CI labels (6CI, 7CI, 8CI, 9CI) have been retained for those names that have them. The CA index names for all substances are being updated in 2007 to comply with the new rules. The previous CA index name, if different, will appear in the OTHER CA INDEX NAMES portion of the REGISTRY display. No names will be removed. New compounds are being named using the new rules.
Highlights of Rule ChangesThe new rules involve changes in locant rules, changes with amino acid and peptide rules, and a number of general rule changes. The following examples illustrate these changes.
Locant Examples: a. Functional suffixes b. Radical locants New Amino Acid Precedence: The new rankings attach greater weight to side-chain functional groups. Also, valine outranks the rare isovaline, and cystine is grouped with its reduced form, cysteine, instead of being separated from it by serine. General Rule Changes: a. More use of ketone parent names b. Silanes ranked between cyclic carbon parents and acyclic carbon parents c. Acyl heteroatom substances named at highest function d. Numerical ratios cited for multicomponent substances
|
