CAS Registry Numbers were first assigned to substances by Chemical Abstracts Service in the 1960s when they created a computerized database of substances to aid their indexers in determining whether a substance in a document they were indexing had previously appeared in the literature. CAS RNs are of the form: xxx-xx-x where the first number is 2-7 digits long, the second number is always two digits long and the third number is a check digit generated by an alogrithm from the previous digits insuch a way that most common mistakes in entering an RN would generate an invalid RN, rather than the RN for the wrong substance.
Every unique chemical substance gets its own RN, including stereoisomers, isotopically-labeled substances, mixtures, etc. One excepption to this is that polymers which only differ in chain length or molecular weight do not get different RNs, nor do plastics which differ only in how tey were processed. This is a long-standing CAS indexing policy, somehwat to the regret of scientists working in the plastics industry.
Note that CAS RNs are purely identification numbers, and do not convey any information about the structure or properties of the substances they represent. Most RNs are assigned by indexers in the course of indexing documents. Some are assigned at the request of chemical manufacturers or government agencies, and represent substances which have no published references. Note, too, that CAS RNs are the property of Chemical Abstracts Service and are not in the public domain. Reaction to this led to the creation of the InChI system (International Chemical Identifier) as an alternative which would be freely available to anyone.
Below is the substance detail for aspirin
Though the CAS REGISTRY File has long contained records for biosequences (proteins and polynucleotides), Now there is Biosequence searching in SciFinder=n, across a file containing the Registry biosences, plus over 550 millionn additional sequences from the patent literature, plus the contents of the NCBI protein and nucleic acid databases, for a total of over one billion searchable biosequences.
Bioscape is a visualization tool for the reults of BLAS Biosequence searches in SciFinder-n. Clicking on the Create Bioscape Analysis button opean aa new window/tab withthe results of the Bioscape analysi. An example is show below.
© 2022 Charles F. Huber
This work by Charles F. Huber is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.
Based on a work at guides.library.ucsb.edu
Screenshots of SciFinder-n are copyright © 2020 by the American Chemical Society and are used under fair use for educational purposes only.