This is how and why the IUPAC nomenclature came to exist in the world of science.

Does the acronym “IUPAC” ring a bell? It doesn’t. But… uh, that was back in school when your science teacher said that carbon dioxide is now carbon (IV) oxide. Remember? We simply hated chemistry, no… it was IUPAC! So what’s the meaning of IUPAC, and how or who on Earth in the name of chemistry came up with such a weird nomenclature?

Well…, all this has to deal with the fact that you don’t speak our language, and neither do we speak yours. Dear friends, it doesn’t matter your language, thanks to IUPAC, you’ll understand chemistry, no matter what you speak.

Whence Cometh IUPAC?

The International Union of Pure and Applied Chemistry is the full meaning of “IUPAC.” It is an international federation of national adhering organizations that represents all chemists from individual countries. The IUPAC was established in 1919 as the international body that represents chemistry and related sciences and technologies. It is a member of the International Science Council (ISC), with its headquarters in North Carolina, United States. 

In 1911, the International Association of Chemical Societies (IACS) — predecessor of the IUPAC — met in Paris, France to discuss issues. This was held by scientists and academicians who recognized a need for standardization in chemistry. The catch?

Let’s say you’re from Techiman and you met a scientific paper written by French scientists. You don’t speak French, duh! So you wouldn’t understand a thing. What about the scientific terminology? These were the issues addressed at the meeting; and henceforth, the IUPAC system of nomenclature was born.


This was to establish a universal system of nomenclature for naming compounds that sought to facilitate easy communication of scientific information. The IUPAC system was to give each chemicals structure a unique and unambiguous name that correlated with a unique and unambiguous structure. And ever since, IUPAC’s mission has provided a common language for chemistry that seeks to promote the free exchange of scientific information.

IUPAC Nomenclature 101

Image: Shutterstock / iStock / Getty Images Plus

Now, let’s do some chemistry. How does the IUPAC system work? Before we get into the nitty-gritty of IUPAC nomenclature, let’s take a crash course on organic chemistry. This is the study of the structure, properties, composition, reactions, and preparation of hydrocarbons — compounds containing (you guessed it), hydrogen and carbon. Other elements include nitrogenoxygenphosphorussiliconsulfur, and the halogens.

There are three main alkyl groups, namely: alkanes (single bonds), alkenes (double bonds), and alkynes (triple bonds). The structure of a compound is determined by its parent group and the number of carbon atoms in that compound.

A structure with only one carbon atoms is named with the corresponding number and the suffix of the alkyl group. For example, methane is a compound that has one carbon atom in the alkane group. The numbering are meth- 1, eth- 2, prop- 3, but-, pent-, hex-, hept-, oct-, non-, and so on.

Image: Shutterstock / iStock / Getty Images Plus | molecular structure of methane, a tetrahedral

The nomenclature is based on naming the longest chain of carbon molecules connected by single bonds — whether in continuous chain or in a ring. For instance, take the IUPAC name “2,5,5-trimethyl-2-hexene,” which has the molecular structure “C9H18.”

In this example, the longest chain of carbon atoms of the double bond has a length of five. But in total, there are nine carbon atoms, and there is a seven-carbon chain, but it contains only one of the double bond carbon atoms. Consequently, the root name of this compound will be pentene.

Organic compound structure of 2,5,5-trimethyl-2-hexene

However, all deviations — either multiple bonds or atoms other than carbon and hydrogen — are indicated by prefixes or suffixes according to a specific set of priorities. The IUPAC name of the compound is written out with the substituents in alphabetical order, followed by the base name (as derived from the number of carbon atoms in the parent chain). There are commas placed in between the numbers and dashes between the letters and numbers. But there are no spaces in the name.

Pop Quiz: But We’ll Keep It Simple

Let’s now go back to chemistry class. What’s the organic structure for …, and the organic name for …? It sucks, huh? Sorry, IUPAC does. Whatever. According to the IUPAC nomenclature, there are about 14 rules for writing a chemical name or structure. Sounds too much?

Naming of compounds in organic chemistry is really important in order to identify that specific name or structure. Misallocating a single carbon atom in the chain could spell out a different compound all together. Take note: if you’re not a chemist, don’t worry, that’s not your duty.

Image: Shutterstock / iStock / Getty Images Plus

Here are a few steps to follow when naming a compound or structure:

Step 1: Find the longest carbon chain in the compound.

Step 2: Name that longest carbon chain.

Step 3: Figure out what the suffix (ending name) should be.

Step 4: Number the carbon atoms.

Step 5: Name the side groups.

Step 6: Put the side groups in alphabetical order.

Let us know the organic structure and name in the comments.

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Written by: Nana Kwadwo, Wed, Jan 12, 2022.

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