Chemists Develop System for Assigning Names to Medication

Organic chemistry is a huge field. Many people don’t grasp just how large it is. The reason for organic chemistry’s large purview lies in the peculiarities of the carbon atom. Carbon is the focus for organic chemists; if a molecule doesn’t have carbon in it, we’re probably not interested in it. Carbon is unique amongst the elements in that it can form stable bonds to other carbon atoms. This is a valuable and rare talent. Take oxygen, for example. The oxygen that we breathe is a molecule made up of two oxygen atoms. If electricity is passed through a sample of oxygen, ozone is formed. Ozone has three oxygen molecules linked to each other, and it’s very unstable, decomposing with a half life of about an hour. Carbon, on the other hand, can form carbon-carbon bonds that are extremely stable and do not decompose. Saran Wrap is a polymer of ethylene, meaning that there are hundreds and thousands of carbon-carbon bonds, all linked up to each other in a huge chain. This molecule is very stable. Carbon can form complicated structures with ease.

The chemists who produce these molecules are charged with naming their creations. There is a system of naming molecules which is collectively known as “nomenclature”. It’s systematized and overseen by an organization known IUPAC, which is the International Union of Pure and Applied Chemistry. IUPAC publishes rules for nomenclature which every organic chemist has to learn. Using these systematic rules, in theory any molecule can be assigned a name that belongs to that molecule alone. No molecule can share the same IUPAC name, because then there would be immense confusion. In the early days of organic chemistry, there were reagents such as “oil of vitriol” and “essence of sulfur”. It was difficult for early chemists because their sample of oil of vitriol may not be the same as someone elses sample, because the name might be applied to two different molecules. The IUPAC system brings in a systematic set of rules which end the confusion. However, IUPAC runs into trouble when the molecule is large. While nomenclature exists to name large molecules, their names are unwieldy and almost impossible to use as a molecular name.

As an example, take the medication named Lexapro. “Lexapro” rolls off the tongue, and it’s easy to pronounce. Compare it to the IUPAC name for the Lexapro molecule, which is: (S)-1-(3-(dimethylamino)propyl)-1-(4-fluorophenyl)-1,3-dihydroisobenzofuran-5-carbonitrile. That’s precise and exact, but it’s not going to be used in common communication. There has to be a system setup to give complicated molecules such as Lexapro a common name. It turns out that there is an organization responsible for doing this. Named USAN (the U.S. Adopted Names Council), they are charged with assigning simple names to the complicated structures of drugs. A recent article in the trade journal Chemical and Engineering News gave an overview of the problem. The council reviews the structure of the molecule and it’s intended purpose, and then assigns a generic name using the stems of words to reflect the purpose of the drug. The Lexapro molecule becomes “Escitalopram”. The common names also describe the shape of the molecules. You see common endings in related drugs, for example diazepam, alprazolam, and clonazepam (Valium, Xanax, and Klonopin) which are all sedatives.

This article was short, but it was an interesting read. Communication is everything in science. If I go into the lab and prepare a sample of a new molecule that has never been made before, I have to assign it a name that accurately reflects the structure of the molecule. That way I can put that name on paper and share it with other scientists, who can then decipher the structure from simply the text. However, in common usage with my fellow chemists and my supervisor, I need to be able to use common terms to identify complicated molecules. IUPAC is nice, but the common words are so much easier. It’s a battle for chemists, because we have to make absolutely sure there is no confusion when we give the name of a new molecule. It’s a battle between IUPAC and USAN that will likely continue far into the future, as the molecules become more and more complicated and the names just get longer. I’m interested to see how things will end up; the field is wide open for a nomenclature system that is both accurate and simple.

The source of this article can be found at:

Drahl, C. “Where drug names come from”. C&E News 2012, 90, 36-37.

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