Naming Esters - Online Tutor, Practice Problems & Exam Prep

Esters are organic compounds characterized by an alkyl group connected to an oxygen atom and a carbon chain with a carbonyl group. Their naming involves modifying the carboxylic acid suffix "oic acid" to "ate." Common naming follows a similar pattern, starting with the alkyl group followed by the carbon chain name, ending in "ate." For example, a propyl group attached to a valerate results in "propyl valerate." When multiple substituents are present, they are named in alphabetical order, with prefixes indicating quantity, such as di- for two or tri- for three.

IUPAC Rules for Naming Esters Concept 1

Now recall esters possess an oxygen atom connected to an alkyl group, so a carbon group, and a carbon chain containing a carbonyl group. So esters have this as the portion that indicates what they are. Now, esters have a unique naming system. The carbon chain with the carbonyl group is named as though it was a carboxylic acid, but it's not a carboxylic acid anymore, it's an ester, so we have to modify the ending. So we're going to modify the ending from oic acid, which is the ending of a carboxylic acid, to oate, which is now the end of the name for an ester. In terms of our naming convention, we still talk about our substituents, and we'll see how that works in terms of esters. We'll have our parent chain where we modify the ending to oate. So keep this in mind as we start naming different types of esters.

IUPAC Rules for Naming Esters Example 1

Provide the systematic name for the following ester. To do that, we're going to utilize the following steps:

1. We have to identify the alkyl group connected to the oxygen atom, and we're going to name the alkyl group as a substituent. Now, when it comes to this alkyl group connected to our oxygen, no numerical location for the alkyl group is needed. So if we take a look here, I've highlighted the portion that's the alkyl group. So here it's a 2-carbon alkyl group, which is ethyl.
2. We identify the carbonyl chain connected to the carbonyl group. The carbonyl group is highlighted in yellow here.
3. Figure out the length of the carbon chain starting from the carbonyl group. Here I've already numbered it for us, so we start here, 1, 2, 3, 4. The carbonyl group is Carbon number, as Carbon number 1 is implied.
4. Now, here we have to assign numbers for the location of each substituent on the carbon chain with the carbonyl group. Here we have, as our substituent, this methyl group down here. When there is more than one identical substituent, we use the prefixes of 'di' for 2, 'tri' for 3, and 'tetra' for 4. So here, we have a methyl group. And remember, this is our original one, the alkyl group which is ethyl.
5. We name all substituents in alphabetical order, prefixes do not count. And here, we're going to use commas to separate numbers from numbers, and we're going to use dashes to separate letters from numbers. We do not separate letters from letters, and this is important.
6. Here, an additional step we have to take into mind is where we write the alkyl group name with spaces.

So, let's put all this together. Since 'e' comes before 'm', it's going to be ethyl. Remember this, we write it with spaces. Then we're going to have what? On carbon number 3 of the carbon chain, we're going to have a methyl so 3-methyl. And then here it's a 4-carbon chain, which is butane, and as a carboxylic acid, it would have been butanoic acid. But remember, we're changing this to 'ate'. So it becomes butanoate. Therefore, it would be ethyl 3-methyl butanoate, and that would be the name of this particular ester.

Provide the systematic name for the following ester. 

• A. propyl butanoate
• B. butyl propanoate
• C. isopropyl butanoate
• D. isobutyl propanoate

Provide the systematic name for the following ester. 

• A. tert-butyl 3,3-dimethylpentanoate
• B. sec-butyl 3,3-dimethylpentanoate
• C. tert-butyl 4,4-dimethylpentanoate
• D. isopropyl 3,3-dimethylpentanoate

If the substituent name of benzene is phenyl, which structure represents phenyl propanoate?

• A.
• B.
• C.
• D.

Common Naming: Esters Concept 2

When it comes to the common naming of esters, we're going to follow the same rules as IUPAC, except now the parent chain consists of common name prefixes with an -ate ending. So the naming convention will be substituent, prefix, and then modifier. Let's take a look at this example. It asks us to provide a common name for the following ester:

1. Identify the alkyl group connected to the oxygen atom. Looking at the structure, the alkyl group is a 3-carbon chain named propyl, which we name as a substituent. Remember, substituents are named at the beginning of the name. Here, no numerical location for the alkyl group is needed because it is attached directly to an oxygen, not a carbon.
2. Identify and name the carbon chain including the carbonyl group. We figure out the length of the carbon chain starting from the carbonyl group, which as carbon number 1 is implied. In this case, there are 5 carbons. For common names, a 5-carbon chain uses the prefix valer-, and since it is an ester, we use the ending -ate, resulting in valerate.
3. Assign numbers to the locations of each substituent on the carbon chain with the carbonyl group. When more than one identical substituent is attached, use prefixes such as di- for 2, tri- for 3, and tetra- for 4. Name all substituents in alphabetical order, noting that prefixes do not count.

Now, valerate is the name of the carbon chain including the carbonyl group. Attached to carbon number 2, there is an isopropyl group. Thus, this substituent makes it '2-isopropyl valerate'.

Finally, commas are used to separate numbers from numbers, and dashes are used to separate letters from numbers. Letters are not separated from letters. Remember to write the alkyl group name with spaces.

So, bringing it all together, the alkyl group attached to the oxygen was propyl, placed at the beginning of the name. The complete name of the ester is 'propyl 2-isopropyl valerate'. This indicates that this propyl portion is connected to the oxygen of the ester, and the rest, highlighted in red, is part of the main chain that contains a carbonyl group. This is the approach we take when naming esters using a common naming system.

Provide common name for given compound.

• A. cyclopentyl-4,4-dimethyl valerate
• B. cyclopentyl 4,4,4-trimethyl butyrate
• C. cyclopentyl 4,4-dimethyl valerate
• D. cyclopentyl-4,4,4-trimethyl butyrate

Give a common name for the following compound.

• A. tert-butyl benzoic acid
• B. butyl benzoate
• C. tert-butyl benzoate
• D. sec-butyl benzoate

Draw structure for given name: hexyl 3-chlorobutyrate.

• A.
• B.
• C.
• D.

Here’s what students ask on this topic:

What is the general structure of an ester?

An ester is an organic compound characterized by an alkyl group connected to an oxygen atom, which is also bonded to a carbon chain containing a carbonyl group. The general structure can be represented as RCOOR', where R and R' are alkyl or aryl groups. The carbonyl group (C=O) is bonded to the oxygen atom, which in turn is bonded to another carbon chain or alkyl group. This unique structure gives esters their distinctive properties and naming conventions.

How do you name esters using the IUPAC system?

In the IUPAC system, esters are named by modifying the name of the corresponding carboxylic acid. The suffix 'oic acid' of the carboxylic acid is changed to 'ate.' The alkyl group attached to the oxygen atom is named first, followed by the modified name of the acid. For example, if the ester is derived from acetic acid and has a methyl group attached to the oxygen, it is named methyl acetate. The general format is: [Alkyl group] [acid name with 'ate' ending].

What are the steps to name an ester using common names?

To name an ester using common names, follow these steps: 1) Identify the alkyl group attached to the oxygen atom and name it. 2) Identify the carbon chain with the carbonyl group and name it using common name prefixes, ending with 'ate.' 3) Combine the names, starting with the alkyl group followed by the carbon chain name. For example, for an ester with a propyl group attached to a valerate chain, the name would be propyl valerate. If there are multiple substituents, list them in alphabetical order with appropriate prefixes (di-, tri-, etc.).

How do you handle multiple substituents when naming esters?

When naming esters with multiple substituents, follow these steps: 1) Identify and name each substituent. 2) Assign a number to each substituent based on its position on the carbon chain, starting from the carbonyl carbon as position 1. 3) Use prefixes like di-, tri-, and tetra- to indicate the number of identical substituents. 4) List the substituents in alphabetical order, ignoring the prefixes when alphabetizing. For example, if an ester has two methyl groups on the second carbon of a butanoate chain, it would be named dimethyl butanoate.

Why don't we need to specify the location of the alkyl group attached to the oxygen in esters?

In esters, the alkyl group attached to the oxygen atom does not require a numerical location because it is always directly bonded to the oxygen. Unlike other functional groups that can attach to different positions on a carbon chain, the alkyl group in esters has a fixed position. Therefore, specifying its location is unnecessary, simplifying the naming process. For example, in ethyl acetate, 'ethyl' is understood to be attached to the oxygen without needing further clarification.