Naming Aldehydes - Online Tutor, Practice Problems & Exam Prep

Aldehydes are carbonyl compounds with a carbonyl carbon bonded to a hydrogen atom. They are named by modifying the alkane name, changing the ending from "e" to "al," with the carbonyl carbon always numbered as 1. For simple aldehydes, common names use prefixes based on the number of carbons: 1 carbon is "form" (formaldehyde), 2 carbons is "acet" (acetaldehyde), 3 is "propion," 4 is "butyl," and 5 is "valer." Substituents are named with their numerical locations, following the longest carbon chain rule, leading to names like "2-chloro butyraldehyde."

IUPAC Rules for Naming Aldehydes Concept 1

Now recall that aldehydes possess a carbonyl carbon connected to an H atom. The set of rules for naming aldehydes is similar to ketones. The exception here, though, is that the carbonyl carbon of the aldehyde is always numbered 1. So that's where we're going to start numbering our longest carbon chain, at the carbonyl carbon of the aldehyde. Here, because we have an aldehyde, a new functional group, we're going to have to modify our ending. We're going to modify the 'e' ending of the original alkane name to 'al', because it's an aldehyde. In terms of our naming convention, we'd still have to give the locations of our substituents, the numerical locations. We'd have to check our parent name with its modified ending, where we're changing 'e' to 'al'. So keep this in mind as we investigate all these different types of aldehydes.

Naming Aldehydes Example 1

Provide a systematic name for the following aldehyde. Now, in order to do this, we're going to utilize the following steps:

• Step 1. Find the longest carbon chain, which will represent the parent chain and assign a name according to the prefixes and modifier. The parent chain should include the aldehyde group and a greater number of carbons. If there is a tie between longest chains, choose the chain with more substituents. In this example, we need to include our carbonyl carbon as part of the longest carbon chain. Remember, in terms of numbering, we start numbering from that carbon. Our longest carbon chain would be here. If we look, this is not part of the longest carbon chain because this is our branch group, our alkyl group. It's made up of 2 carbons, so this would be ethyl. We've assigned names to all the substituents.
• Step 3. Start numbering the chain at the carbon of the aldehyde group. This would be: 1, 2, 3, 4, 5, and 6.
• Steps 4 to 6, repeat steps from previous naming topics. If you haven't watched my video on alkane with substituents, I suggest that you go back and take a look. There we talk about steps 4 to 6, where we're basically paying attention to these substituents. We have to give the numerical locations of our substituents, and make sure we name them alphabetically. It also explains how we set up the name, where we use commas to separate numbers and dashes to separate numbers from letters. So here we have an ethyl on carbon 2, so it would be 2-ethyl. Because the aldehyde carbon always gonna be carbon number 1, we don't need to designate where it's located.

So we have a 6 carbon chain, which in alkane form is hexane, but remember, we're changing the 'e' to 'al.' Therefore, the name of this particular aldehyde would be 2-ethylhexanal.

Provide the systematic name for the following aldehyde. 

• A. 4-fluoro-5-methylheptanal
• B. 4-fluoro-5-ethylhexanal
• C. 4-fluoro-5-methylheptanone
• D. 4-fluoro-5-ethylhexanone

Which of the following compounds represent 2-bromo-pentanal?

• A.
• B.
• C.
• D.

Common Naming: Simple Aldehydes Concept 2

So when it comes to the common naming rules for simple aldehydes, we say that simple aldehydes are named using common names. Here, we're going to use a prefix with an aldehyde suffix. Now, we're going to say these prefixes are utilized in common names by many carbonyl compounds. Here, if we look at the number of carbons, 1 to 5, we're going to say that if you have one carbon, your prefix is 'form.' So as an aldehyde, you have formaldehyde. If you have 2 carbons, it's 'acet,' so you'd be acetaldehyde. And then here for 3 and 4, remember 3 carbons is propane. So this is a play on that. That's this is 'propion.' Four carbons is butane. Here we have 'butyl.' So it's a little play on those 3 and 4 carbons. 5 is very different. Here we have 'valer.' So just think of the Roman numeral, V. V stands for 5. So that's why it's related to 5 carbons. Alright. So, again, this applies to simple aldehydes going from 1 to 5 carbons. And we'll see how to name them and utilize these prefixes with an aldehyde suffix.

Naming Aldehydes Example 2

Here it says, name the following aldehyde using a common naming system. So if we look here, here's our carbonyl and that's part of the aldehyde. It's 1, this is 2, and this is 3. So this is a 3 carbon aldehyde. So remember, the prefix would be propion, and then we end it with aldehyde for the suffix. So the propionaldehyde as the common name for this particular aldehyde.

Common Naming: Substituted Aldehydes Concept 3

Now when it comes to the common naming of aldehydes, and the aldehydes are substituted, we're going to follow the following rules. Right. We're going to say the substituents are designated with a numerical location. So we have the location of where the substituent is attached on the chain, but of course, we're still remembering the prefix when it's 1 to 5 carbons, and then remember ending it with the suffix aldehyde. So if we take a look here, we say name the following aldehyde using the common naming system. So here we have our chain, and on it we have this chlorine group. So when we follow the rules, we're going to say step 1 is to find the longest carbon chain. Remember, we learned about prefixes from 1 to 5 carbons. So we're basically applying these rules to those types of aldehydes. And we're going to assign a name according to the common name in terms of its prefix and suffix. Now the carbon chain should include the aldehyde group and have the most number of carbons. Now if I tie between longest chains, choose the chain with more substituents. So if we look here, the longest chain is 1, 2, 3, 4, four carbons. And remember, when it comes to the prefix, we're going to say that is butane. And we're going to end the name with aldehyde. Okay. So that's the name of the longest aldehyde chain. Step 2 is to assign a name to all substituents. This is a chlorine, and chlorine is chloro. Step 3, we're going to start numbering the chain at the carbon of the aldehyde group, which we already did. And step 4 to 6, repeat the steps from previous naming topics. Alright. So we already named the chain of the aldehyde group, we just now need to state the location of the chloro. It is on carbon number 2, so this would be 2-chloro butanal. Alright? So this will be the name of this particular common aldehyde.

Provide common name for following aldehyde.

• A. 3,3-dimethylbutyraldehyde
• B. 2,2-dimethylvaleraldehyde
• C. 1,1-dimethylvaleraldehyde
• D. 2,2-dimethylpentanal

Provide common name for given molecule.

• A. 3-ethylbenzylaldehyde
• B. 2-ethylbenzylaldehyde
• C. 3-ethylbenzaldehyde
• D. 2-ethylbenzaldehyde

Here’s what students ask on this topic:

What are the rules for naming aldehydes in organic chemistry?

Aldehydes are named by modifying the name of the parent alkane. The carbonyl carbon is always numbered as 1. The suffix 'e' of the alkane is replaced with 'al'. For example, methane becomes methanal. If there are substituents, their positions are indicated by numbers, starting from the carbonyl carbon. For instance, 2-chlorobutanal indicates a chlorine substituent on the second carbon of butanal. Common names for simple aldehydes use prefixes based on the number of carbons: 1 carbon is 'form' (formaldehyde), 2 carbons is 'acet' (acetaldehyde), 3 is 'propion', 4 is 'butyl', and 5 is 'valer'.

How do you name aldehydes with substituents?

To name aldehydes with substituents, follow these steps: 1) Identify the longest carbon chain that includes the aldehyde group. 2) Number the chain starting from the carbonyl carbon, which is always numbered as 1. 3) Name the parent chain by replacing the 'e' ending of the alkane with 'al'. 4) Identify and name the substituents, indicating their positions with numbers. For example, in 2-chlorobutanal, 'butanal' is the parent chain, and '2-chloro' indicates a chlorine substituent on the second carbon.

What is the common name for an aldehyde with three carbons?

The common name for an aldehyde with three carbons is propionaldehyde. In the common naming system, the prefix 'propion' is used for three-carbon aldehydes, followed by the suffix 'aldehyde'. This naming convention is based on the number of carbons in the aldehyde chain.

How do you determine the longest carbon chain in an aldehyde?

To determine the longest carbon chain in an aldehyde, follow these steps: 1) Identify the carbonyl carbon, which is always numbered as 1. 2) Count the number of carbons in the longest continuous chain that includes the carbonyl carbon. 3) If there is a tie between chains of equal length, choose the chain with the most substituents. This chain will be used to name the aldehyde, ensuring the carbonyl carbon is always part of the chain.

What is the IUPAC name for formaldehyde?

The IUPAC name for formaldehyde is methanal. In the IUPAC naming system, aldehydes are named by replacing the 'e' ending of the parent alkane with 'al'. Since formaldehyde has only one carbon, the parent alkane is methane, and the name becomes methanal.