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What You Didn’t Know About the History of Chemical Nomenclature and ACD/Labs

January 31, 2024
by Jesse Harris, Digital Marketing Coordinator, ACD/Labs

History of Chemical Nomenclature and ACD/Name

When ACD/Name, our nomenclature software package, first arrived on the market in 1996, it offered naming in English and was able to generate the correct names for basic organic structures. Since then, a lot has changed, both in the world of chemistry and in ACD/Name. Today, the software can generate names for organic, biochemical, and some inorganic structures in over 20 languages in just a fraction of a second per structure.

Names for structures are not retrieved from a database; they are generated by applying algorithms based on the rules of nomenclature. Our well-developed set of procedures, based on years of development, testing and revisions, can produce the correct name for a wide range of structures, even those that have never been synthesized. As scientists push the boundaries of the known world, we must keep evolving our tools to serve their needs.

Updates are essential to keep software relevant, and this is truer than ever for today’s world of chemical R&D. We previously wrote about identifying the ‘most correct’ name for a compound, and how developments in the field of chemical compounds have required an update in the rules designed to classify them. ACD/Name provides chemical naming based on the current IUPAC nomenclature recommendations and supports Index name generation closely following CAS nomenclature. What’s the difference? Read on below.

IUPAC Chemical Nomenclature

IUPAC, the International Union of Pure and Applied Chemistry, was founded in 1919 and is the “universally-recognized authority on chemical nomenclature and terminology.” The IUPAC Recommendations on the Nomenclature of Organic Chemistry (IUPAC Blue Book) provide naming principles for all classes of organic compounds and continue to evolve with the growing complexity of chemical objects and need for unique and unambiguous names.

ACD/Labs produced an electronic version of both the 1979 and 1993 recommendations—incorporating them into the software interface of ACD/Name and hosting them on our web site here. This reference is a popular and useful resource allowing scientists to interpret older names, which are often used in both printed and electronic sources.

The IUPAC rules are always intended to ensure that each name refers to a unique molecule. This is critical since there are serious safety and legal risks if one chemical is confused with another. However, this does not necessarily mean that each substance may have only one name. For example, several names can correctly define the structures below, but only one name is the preferred IUPAC name.



The most recent edition of the IUPAC Blue Book was published in 2014, providing updated guidelines for naming chemical compounds and introducing the concept of Preferred IUPAC Names (PINs).

While not as great of a risk as mistaking one chemical for another, multiple names for the same molecule can still cause confusion. The new IUPAC recommendations allow choosing a unique name for each structure, establishing conventions to determine the preferred name. The use of PINs is encouraged, especially in academic publications, patents, and other legal documents.

In the upcoming version of ACD/Name (expected this winter), we will integrate the full text of the current IUPAC organic nomenclature recommendations (Blue Book 2013). Users will be able to see the specific rules that were used to create a given name and read the relevant sections of the recommendations.


Chemical nomenclature includes many procedures, some of which are difficult for both humans and computers. There is still room for improvement in algorithmic chemical nomenclature, which is why some generated names do not correspond to a PIN. ACD/Labs continues to develop our software to better adhere to the IUPAC recommendations.

Two nomenclatures: CAS and IUPAC—Proprietary vs. Public

While having a common origin, IUPAC and CAS nomenclatures today have many differences that are noticeable even in names for simple structures. CAS, a division of the American Chemical Society, maintains the CAS Registry® database containing records for millions of substances, each identified with a CAS Registry Number®, CAS Index name, and synonyms. It should be mentioned that in contrast to IUPAC, CAS nomenclature is intended to provide only one unique name for each chemical.

While the general principles of CAS nomenclature are published, the details remain proprietary. Still, following the available sources and official CAS names, we created the necessary algorithms to allow ACD/Name to generate Index names that in many cases correspond to official CAS Index names. Note that an Index name generated by ACD/Name should not be mistaken with a CAS name that is obtained from CAS official sources.

Nomenclature in Implementation and Development

2024 marks the 30th anniversary of both ACD/Labs as a company, and the start of development for ACD/Name. Chemical nomenclature is a complex scientific area that is challenging for humans, not least because it is constantly evolving. Even when we think of programming software for this task, the sheer number of nomenclature rules that must be considered is staggering. Developing one set of strict computer algorithms requires as much knowledge of chemical nomenclature as it does of computer programming. We are proud of our team of experienced chemists and programmers, whose efforts have produced a naming software that surpasses most human experts in scope, accuracy, and productivity.
In our work with chemical nomenclature, we not only implement the published rules, but we also detect areas of nomenclature that are not fully defined or lack the necessary criteria to produce a single preferred name. We are happy to have a history of intensive collaboration with IUPAC Chemical Nomenclature and Structure Representation Division via Dr. Andrey Yerin, who has led the ACD/Name project since its inception. He has been involved with numerous chemical nomenclature projects during his decades-long career as a member of several IUPAC nomenclature bodies.

In this way, ACD/Labs not only implements chemical nomenclature but participates in its development via algorithmic verification of new principles and making proposals for further improvements.

Nomenclature Beyond Just Names

Another nomenclature task is generating a structure from a given name. While this is generally considered to be easier than chemical naming, it is at least as tedious and prone to errors. This is why ACD/Name includes its companion Name to Structure tool, since not every generated name can produce a structure, and vice versa. Name to Structure also benefits from the ACD/Dictionary, a database of over 170,000 chemical names and registry numbers for thousands of drugs, pesticides, and other registered substances.

Chemical names, while still having a very important role in compound identification and registration, have gradually become less convenient to use due to difficulties in name generation and interpretation. One groundbreaking project undertaken by IUPAC was the introduction of the IUPAC International Chemical Identifier (InChI). InChI is a non-proprietary identifier for chemical substances that can be used in printed and electronic documents, which enables easier linking of diverse data sources.

When the InChI identifier was introduced, ACD/Labs was among the first to provide an integration between a drawing package and the InChI software components. We also offer the ‘reverse’ InChI-to-Structure conversion and the InChI Key, fully integrating InChI with our nomenclature toolset, structure drawing, and databasing packages. ACD/Labs is a member of the InChI Trust and our team participates in the testing of new versions and contributes to the development of InChI tools by participating in several related IUPAC projects and initiatives.



Continued developments in nomenclature are changing many chemical names as we used to know them. This is proof that the field of chemical nomenclature is ever evolving. We’re delighted that researchers, IP lawyers, teachers, and students all over the world use ACD/Labs nomenclature tools every day.

This continued drive to incorporate all the developments in the rapidly changing world of chemistry over the decades has resulted in Name being the best nomenclature software available, proving what was stated of it in a 2006 Molecules article by Gernot Eller.

“When compared with other naming software…the quality of names generated from ACD/Name is second-to-none.”
G. Eller,
Molecules, 11:915–928, 2006

We continue to add new features to Name every year and work closely with IUPAC’s experts to remain abreast of new developments.


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