Every chemical is assigned a CAS Number. Have you ever wondered what a CAS Number is and how they are assigned?
Check out this very simple explanation that will give you everything you need to know about what a CAS Number is, plus how CAS Numbers are assigned.
CAS No. abbreviated as Chemical Abstracts Service number is given to every chemical compound that has been in existence from early 1900 to date by The Chemical Abstracts Service Registry. It is part of the American Chemical Society, and the numbers given to compounds are in the sequence of new substances identified.
What are CAS Numbers?
CAS Numbers are between 5 – 12 digits using the format xxxxxxx-yy-z. They are assigned to a compound as the CAS registers a new compound. The number has no significance to the chemistry, structure, or chemical nature of the molecule.
The CAS Number of a compound is a useful way to identify a chemical over its name. For example, the compound CAS 5781-53-3 refers to Methyl Oxalyl Chloride. Methyl Oxalyl Chloride is also known as Methyl chloroglyoxylate, Methyl chlorooxoacetate, methyl 2-chloro-2-oxoacetate, Methyl (Chlorocarbonyl)formate, or methoxyl chloride. The CAS Number is the same for all these names.
The CAS Number can also be used to distinguish between stereoisomers of a compound. Glucose is a sugar molecule that has two forms: D-glucose and L-glucose. D-glucose is also called dextrose and has CAS Number 50-99-7. L-glucose is the mirror image of D-glucose and has a CAS Number of 921-60-8.
Relevance of the number, to the chemical :
The numerical representation of a compound is through a max of 12 digits, with hyphens to separate it into three parts. The right-most digit is the one to verify the validity and uniqueness of the number and is referred to as the check digit. CAS number is unique to a compound and does not have any significance to its chemical formula or to the compound.
How is the CAS No. helpful?
The important aspect of following CAS numbers is to rule out the confusion in identifying compounds and having access to a trove of information.
It is the most reliable platform used across the globe and serves as a common link between various nomenclature terms that describe substances. Validation is quick and dependable.
An example to explain the practicality of CAS No. :
Methyl Oxalyl Chloride, a pervasive chemical, is known by several names :
● Methyl chloroglyoxylate
● Methyl chloroacetate
● methyl 2-chloro-2-oxoacetate
● methyl chlorooxalate
● methoxyl chloride
● Methyloxalylchloride Etc…
Its formula can be written in various forms like C3H3ClO3 or CH3Cl. With so many different ways of referring to a single compound, clarity can be attained with its CAS No. which is 5781-53-3, an easy identification to clear the confusion.
The cited example is a simple representation but distinguishing between stereoisomers with CAS No. is a boon and the quick & trusted way to identify each compound.