In the vast and complex world of chemistry, precise identification of chemical substances is paramount. Whether you are a procurement specialist sourcing raw materials, a researcher developing a new compound, or a regulatory expert ensuring compliance, a universal identifier for each chemical is indispensable. This is where Chemical Abstracts Service (CAS) Registry Numbers, commonly known as CAS numbers, play a critical role. Understanding what CAS numbers are and how they function is essential for anyone involved in the chemical and pharmaceutical industries.

A CAS Registry Number is a unique, numerical identifier assigned by the Chemical Abstracts Service, a division of the American Chemical Society. It is assigned to every chemical substance described in the open scientific literature. These numbers are composed of three parts, separated by hyphens, in the format NNNNN-NN-N. For example, a well-known pharmaceutical intermediate, 4'-tert-Butyl-4-chlorobutyrophenone, is identified by CAS number 43076-61-5. This numerical system ensures that each chemical substance, regardless of its common name, trade name, or structural description, has a singular, unambiguous identifier.

The primary benefit of CAS numbers lies in their ability to eliminate ambiguity. Many chemicals can have multiple common names, synonyms, or systematic IUPAC names, which can lead to confusion, especially in international trade and research. For instance, a chemical might be known by its trade name, a common laboratory name, and its official chemical name. However, its CAS number remains constant, providing a definitive link to that specific substance. This is invaluable when searching databases, ordering chemicals, or reporting safety data.

For buyers and researchers, CAS numbers are a fundamental tool. When sourcing a chemical, specifying the CAS number in your inquiry to a manufacturer or supplier ensures you are looking for the exact substance you need. For example, when requesting a quote for 4'-tert-Butyl-4-chlorobutyrophenone, including 'CAS 43076-61-5' leaves no room for misinterpretation. This prevents costly errors and ensures that the product received matches the required specifications and intended application, whether for research purposes or bulk purchase for manufacturing.

Furthermore, CAS numbers are integral to regulatory compliance and safety data. Chemical safety data sheets (SDS), hazard labels, and regulatory documents all typically feature the CAS number as a primary identifier. This facilitates communication between manufacturers, distributors, users, and regulatory bodies, ensuring that everyone is referring to the same substance when discussing its properties, hazards, and handling procedures. It aids in tracking chemicals throughout their lifecycle and ensuring safe usage.

The CAS Registry is one of the most comprehensive and authoritative chemical databases in the world, constantly updated as new substances are discovered or synthesized. This ongoing dedication to accurate identification makes CAS numbers an indispensable resource for anyone navigating the chemical landscape. Whether you are looking to buy a specific reagent, verify a compound's identity, or ensure regulatory adherence, always rely on the definitive CAS number as your primary identifier.