Naming Carboxylic Acids: Study with Video Lessons, Practice Problems & Examples

Carboxylic acids feature a carbonyl carbon linked to a hydroxyl group, with naming conventions similar to aldehydes. The suffix changes from 'e' to 'oic acid'. Dicarboxylic acids, containing two carboxyl groups, use the suffix 'dioic' in IUPAC naming. Common names often utilize the mnemonic "Oh my such good apple pie" for acids like oxalic and adipic acid, which have practical applications. Understanding these naming conventions and structures is essential for grasping organic chemistry concepts, particularly in relation to functional groups and their reactivity.

IUPAC Rules for Naming Carboxylic Acids Concept 1

Now recall that carboxylic acids possess a carbonyl carbon connected to a hydroxyl group. So your hydroxyl group is an OH group. So we have a carbonyl connected to OH. Now the set of rules for naming carboxylic acids are similar to aldehydes. That's because, just like an aldehyde, the carbonyl carbon, in the case of a carboxylic acid, is always number 1. Now here, we're going to modify the 'e' ending of the original alkane to 'oic acid'. Because it's not an alkane, it's a carboxylic acid, so 'e' becomes 'oic acid.' Our naming convention still requires us to give the locations of our different substituents. Our parent chain would be modified from an 'e' ending to 'oic acid.' Keep this in mind as we start naming different types of carboxylic acids.

IUPAC Rules for Naming Carboxylic Acids Example 1

Provide the systematic name for the following carboxylic acid. Here, to do that, we're going to utilize these steps in terms of naming the molecule before us. So, here's step 1, find the longest carbon chain. This will represent our parent chain, and assign a name according to the prefixes and modifiers. The parent chain should include the carboxylic acid group and a greater number of carbons. Now, if there is a tie between longest chains, choose the chain with more substituents. Alright. So, we're going to find the longest carbon chain. We have to make sure that the carboxylic acid group is part of it. So if we look, this would be the longest carbon chain. We can go this way, or we can go this way. Both would give us the same length for the carbon chain and the same number of substituents. So here, I'm just going to go by the original way, this way.

Now, assign names to all the substituents for step 2. So here, we have a bromine group as a substituent, so this would be bromo. And then here, we have a 3-carbon alkyl group which is an ethyl. Start numbering the chain at the carbon of the carboxylic acid group, so the COOH group. So this would be 1, 2, 3, 4, 5, and 6.

And then steps 4 to 6, we repeat steps from previous naming topics. Mainly, we give numerical locations to the substituents, we make sure that they're named alphabetically in relation to each other, and we make sure we use commas to separate numbers and dashes or hyphens to separate letters from numbers. So here, alphabetically, 'b' comes before 'e'. The bromo is on carbon 3, so 3-bromo. And then we have the ethyl on carbon 4, 4-ethyl. Since the carboxylic acid carbonyl carbon is carbon number 1, we don't have to give it a number designation. So we have a 6-carbon chain which is hexane, but we change the 'e' ending to hexanoic acid here. It becomes 'oic acid', so the name of our carboxylic acid here would be 3-bromo-4-ethylhexanoic acid.

If the substituent name of the OH group is hydroxy in the presence of a carboxylic acid, provide the systematic name for the following compound. 

• A. 5-ethyl-4-hydroxyoctanoic acid
• B. 4-ethyl-5-hydroxyoctanoic acid
• C. 5- isopropyl-4-hydroxyoctanoic acid
• D. 4-isopropyl-5-hydroxyoctanoic acid

Common Naming: Carboxylic Acids Concept 2

Now, when it comes to the common naming of carboxylic acids, we're going to say a simple carboxylic acid name consists of a common name prefix and ends with ic acid. Here we're going to see that our substituted carboxylic acids utilize Greek letters. So alpha, beta, gamma, delta, and they're going to indicate the location of substituents. Greek symbols are assigned to carbons adjacent to the carboxyl carbon. So that's just the carbon that's the carboxylic acid. We're talking about this carbon here. And remember, one space away is alpha, then beta carbon, then gamma carbon, then delta carbon. We typically do not see anything beyond the delta carbon. Just remember these 4 Greek letters. We're going to utilize them when talking about common names for carboxylic acids.

Common Naming: Carboxylic Acids Example 2

Here it says to provide a common name for the following carboxylic acid. So step 1 says we need to find the longest carbon chain and assign the name according to common name prefixes and endings. Now the parent chain should include the carboxylic acid group and have the most number of carbons. If I tie between longest chains, choose the chain with more substituents. If we take a look at this carboxylic acid, the longest chain would be here. And if we looked at this, it would be 1, 2, 3, 4 carbons. Four carbons for carboxylic acid, the prefix would be butyric, and it's a carboxylic acid, so it's butyric acid, or butanoic acid here would be the common name of the carboxylic acid itself. Now assign names to all substituents. Here we have a chlorine, which would be chloro. Here we have a methyl. Those are our 2 substituents.

Now, we're going to give the number using Greek symbols, which stands for the location for each substituent. Now when there is more than one identical substituent, we use prefixes like di for 2, tri for 3, and tetra for 4, and we name the substituents in alphabetical order. The prefix does not count towards the alphabetical order. Finally, when we put it all together, we are going to use commas between the Greek symbols, and we are going to use dashes to separate Greek symbols from letters. Letters are not separated by spaces.

When numbering the 4-carbon chain, remember this would be the alpha position, then beta, and then gamma. This would be the gamma position. If we look, chloro comes before methyl, so chloro is on the beta carbon, so this would be beta-chloro. Then, the methyl is on the alpha carbon, so this will be alpha-methyl. And methyl butyric acid is all one word. So this would be the name, beta-chloro-alpha-methylbutyric acid. Alright, this would be our final answer.

Provide a common name for following molecule.

• A. 2,5-hydroxybutyric acid
• B. α,β-dihydroxypentanoic acid
• C. 2,5-dihydroxybutyric acid
• D. α,β-dihydroxyvaleric acid

Naming Dicarboxylic Acids Concept 3

So dicarboxylic acids contain 2 COOH groups, so 2 carboxylic acid groups. Now when it comes to the IUPAC naming, we're going to say they have the same rules as carboxylic acids, but you're going to replace the -ic suffix with -dioic. So that's going to be a key difference here for dicarboxylic acids. Another important thing to notice is that when it comes to naming them, the parent chain name is not modified. So if we take a look here at this dicarboxylic acid on the right, we'd say that its IUPAC name would be ethanedioic acid. Notice we did not drop the e in terms of naming this dicarboxylic acid. Its common name would be oxalic acid. Now, common names are often used for dicarboxylic acids and luckily, there's a pretty commonly used memory tool for it. And it is, "Oh my such good apple pie." So if we take a look, "Oh my such good apple pie." So oxalic acid is the simplest dicarboxylic acid. It's just 2 carboxylic acids directly connected to each other. As we increase the length of our chain, all we're doing is adding more CH₂s in the middle. Remember, the CH₂ group is called the methylene group. Alright, so malonic ester or actually malonic acid has one CH₂ that connects the two carboxylic acids to each other. Then we go to succinic acid. All we're doing is just lengthening the chain by adding more and more CH₂ groups. So now we'd have 2 here. And then glutaric acid, add another CH₂, so now there's 3. Adipic acid, so this would be 4. Interesting about adipic acid is that it's a key component when it comes to like nylon stockings. So adipic acid has everyday use applications. Now, and then the last one we have is polymeric acid. So we add another CH₂, so that'd be 5. So just remember, we have IUPAC naming rules for dicarboxylic acids, and then we have these common names for these dicarboxylic acids. And to remember the common names, just remember, oh my such good apple pie.

Naming Dicarboxylic Acids Example 3

Provide a common name for the following carboxylic acid. As we can see, this is a dicarboxylic acid that we're given. The longest chain would be this portion here, and those two methyl groups will be our substituents. So looking at step 1, we find the longest carbon chain and assign a name according to common name prefixes. The parent chain should include both carboxylic acid groups. From there, we follow the rules that we know in terms of naming carboxylic acids. Now here, we're going to say this will be the carboxylic acid we start numbering because it's the one closest to our substituents. So here we'd say 1, 2, 3, 4. We'd say this is 2 carboxylic acids. They're connected to each other by two CH₂s in the middle. Just remember, "oh my, such good apple pie." Which one has 2 CH₂s in the middle? Succinic acid. So here, it would be succinic acid as the common name for this dicarboxylic acid. Then, we'd say this is our alpha since we made this carbonyl, carboxylic acid group, into carbon number 1. This would be the beta position. We don't need to go further than that. So the two methyl groups are at the alpha position. We'd say that this is going to be alpha, alpha-dimethyl succinic acid. From the name, we're going to deduce that both those methyl groups are on the alpha carbon, so that's why we can name it in such a way. Here, if we wanted to continue with the way that we are customizing, you could also say alpha, alpha-dimethyl succinic acid, but that really isn't necessary. Here, when it comes to these dicarboxylic acids, we see dimethyl. We only see one Greek symbol, so we're assuming that both those methyl groups are on that same carbon. Alright, so this will be the name of this particular dicarboxylic acid.

Give IUPAC name for the following dicarboxylic acid.

• A. 3-ethylheptanedioic acid
• B. 5-ethylheptadioic acid
• C. 3-methylhexadioic acid
• D. 5-ethylhexanedioic acid

Draw a structure for the given common name: α-bromo-β-hydroxyadipic acid.

• A.
• B.
• C.
• D.

Here’s what students ask on this topic:

What are the rules for naming carboxylic acids in IUPAC nomenclature?

In IUPAC nomenclature, carboxylic acids are named by identifying the longest carbon chain that includes the carboxyl group. The carbon in the carboxyl group is always assigned as carbon number 1. The suffix of the parent alkane name is changed from 'e' to 'oic acid'. For example, methane becomes methanoic acid, and ethane becomes ethanoic acid. If there are substituents, their positions are indicated by numbers, and they are listed in alphabetical order. For dicarboxylic acids, the suffix 'dioic acid' is used, such as in ethanedioic acid.

How do you name dicarboxylic acids using IUPAC rules?

Dicarboxylic acids contain two carboxyl groups. In IUPAC nomenclature, the parent chain name is retained, and the suffix 'dioic acid' is added. The carbon atoms in the chain are numbered starting from one of the carboxyl groups. For example, a two-carbon dicarboxylic acid is named ethanedioic acid. The common names for dicarboxylic acids can be remembered using the mnemonic 'Oh my such good apple pie', which stands for oxalic, malonic, succinic, glutaric, adipic, and pimelic acids.

What is the mnemonic for remembering common names of dicarboxylic acids?

The mnemonic 'Oh my such good apple pie' helps remember the common names of dicarboxylic acids. It stands for oxalic acid (simplest, with two carboxyl groups directly connected), malonic acid (one CH₂ group between carboxyl groups), succinic acid (two CH₂ groups), glutaric acid (three CH₂ groups), adipic acid (four CH₂ groups), and pimelic acid (five CH₂ groups). This mnemonic aids in recalling the sequence and structure of these acids.

How are Greek letters used in the common naming of carboxylic acids?

In the common naming of carboxylic acids, Greek letters (alpha, beta, gamma, delta) are used to indicate the position of substituents relative to the carboxyl group. The carbon adjacent to the carboxyl carbon is labeled as alpha (α), the next as beta (β), followed by gamma (γ), and delta (δ). For example, in a carboxylic acid with a methyl group on the second carbon, it would be referred to as a beta-methyl carboxylic acid.

What is the difference between IUPAC and common names for carboxylic acids?

The IUPAC naming system for carboxylic acids involves identifying the longest carbon chain containing the carboxyl group and changing the suffix from 'e' to 'oic acid'. For example, ethane becomes ethanoic acid. Common names, however, often use historical or traditional names and may include Greek letters to indicate substituent positions. For instance, ethanoic acid is commonly known as acetic acid. Dicarboxylic acids also have common names remembered by the mnemonic 'Oh my such good apple pie'.