Naming Carboxylic Acids Using IUPAC Nomenclature

Instructor: Amanda Robb

Amanda holds a Masters in Science from Tufts Medical School in Cellular and Molecular Physiology. She has taught high school Biology and Physics for 8 years.

This lesson will help you learn the naming conventions for carboxylic acids using IUPAC rules. First, we'll discuss what carboxylic acids are, then we'll look at the IUPAC nomenclature, and name some examples.

What Are Carboxylic Acids?

Take a minute before reading this lesson and flex your muscles. Feels pretty good right? The reason you can move your muscles is actually partially because of carboxylic acids. Carboxylic acids are organic molecules that contain a carbonyl group, or a carbon bound to an oxygen, and a hydroxyl group.

The general formula for carboxylic acids
carboxylic acid

This type of functional group is present on amino acids, and is the reason we can build proteins like actin and myosin, which are responsible for muscle movement. Carboxylic acids are also found in fats in our body, metabolic products, and used in a wide range of manufacturing industries such as textiles, plastics and rubber. In fact, you probably have some carboxylic acid in your cupboard right now if you have vinegar and some sitting on your bathroom sink if you have hand soap. Carboxylic acids are more versatile than you might think!

IUPAC Nomenclature

The International Union of Pure and Applied Chemistry (IUPAC) sets up standard naming conventions for all types of organic molecules. To name any molecule using IUPAC naming conventions, first we need to be able to name the base carbon chain, called the parent alkane, attached to the group. To do this, there are specific names depending on how many carbons are in the molecule as shown in the table here.

Carbon Length Name
1 Methane
2 Ethane
3 Propane
4 Butane
5 Pentane
6 Hexane
7 Heptane
8 Octane
9 Nonane
10 Decane

To name carboxylic acids, follow these steps.

1. Count the longest carbon chain that contains the carboxylic acid and use the base name from the table here.

2. Change the ending of the parent name from 'e' to 'anoic acid'.

3. Count the carbons so that the carboxylic acid group gets the lowest possible number.

4. Number additional substituent groups, groups attached to the main carbon chain, according to the carbon they branch from. List all substituents in alphabetical order as prefixes prior to the carboxylic acid name.

Examples

Now, let's look at some examples. To start, let's name this carboxylic acid.

An example of a carboxylic acid
carboxylic acid

First, we should count the longest carbon chain that contains the carboxylic acid group. In this case, as you can see in the diagram above, it's five carbons long, so the parent alkane name is pentane. Now, we switch the ending 'e' for 'anoic acid'. Since there are no substituents, this is the only thing we need to do. The final IUPAC name is pentanoic acid.

Now, let's look at another example with substituents. Let's name this compound in the following image.

A carboxylic acid with substituents
carboxylic acid

First, we should count the longest carbon chain that contains the carboxylic acid. This chain has three carbons, so the parent alkane name is propane. We switch the 'e' for 'anoic acid' to get the carboxylic acid name, propanoic acid.

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