Naming Ketones - Online Tutor, Practice Problems & Exam Prep

Ketones are organic compounds characterized by a carbonyl group ($C=O$) attached to two carbon atoms. When naming ketones, the suffix '-one' is used in place of '-e' in the corresponding alkane name to indicate the presence of the carbonyl group. It's crucial to specify the location of the carbonyl group and any substituents on the parent chain to accurately name the ketone. This systematic approach to nomenclature ensures that the structure of the ketone is clearly communicated, reflecting the importance of precision in organic chemistry.

Rules for Naming Ketones

Now recall that ketones possess a carbonyl carbon connected to two carbon atoms. Now here the set of rules for naming ketones are similar to those used for naming alcohols.

Here though the modifier, the ending of E is changed to 1, and when we talk about the naming convention, we still have to give the locations of different substituents. We then have to give the location of the carbonyl group that is part of the parent chain, and then remember that we're doing a modification to the E ending to one.

These are the keys to naming any ketones that we're going to see.

Naming Ketones Example

Here it says provide the formal name for the ketone shown. Now to do that we're going to use the following steps. TE one is find the longest carbon chain which represents our parent chain and assign name according to the prefixes and the modifier. Now the parent change should include the carbonyl group. So remember your carbonyl carbon or carbonyl group is this C2=O and have greater number of carbons. If a tie between longest chain choose chain with more substituents.

If we take a look here, our longest carbon chain will be this portion here. Now assign name to all substituents for Step 2. Our substituent here would be this carbon that's branching off of the main chain. This would be a methyl group. Step three, start numbering the chain from the end closest to the carbonyl carbon. So we have to start numbering from this end 123-4567 and eight.

If a time the number from the end closest to the next substituent, it's still a tie number in alphabetical order in terms of the substituents. And then here assign location to the carbonyl carbon, the carbonyl carbons on carbon #2. All right. And then we repeat steps 4:00 to 6:00. And these are from previous naming topics mainly. If we're looking at alkanes with substituents, that's where we're coming up with these rules.

Or steps 4:00 to 6:00, if you haven't watched that video, make sure you go back and take a look because in it we talk about our substituents. They're written at the beginning of the name. We have to give their location numerical location and if there's multiple substituents, we have to name them alphabetically. So here, if we take a look, we're going to say our substituent is on carbon 5, so it's 5 methyl. The carbonyl carbon is on carbon. 2SO28 carbons is octane, but we change the E ending to 1 so it becomes 2 octanone. So this would be the name of this particular ketone 5 methyl 2 octanone.

Provide the systematic name for the following ketone.

• A. 4,4-dichloro-2-hexanone
• B. 3,3-dichloro-2-hexanone
• C. 4,4-dichloro-5-hexanone
• D. 3,3-dichloro-5-hexanone

Which of the following compounds represent $2,4-dimethyl-3-pentanone$?

• A.
• B.
• C.
• D.

Here’s what students ask on this topic:

How do you name a ketone?

Naming a ketone in organic chemistry follows the International Union of Pure and Applied Chemistry (IUPAC) nomenclature rules. Here's a simple guide to name a ketone:

1. Identify the longest carbon chain that includes the carbonyl group (C=O). This chain determines the base name of the ketone.
2. Number the carbon chain starting from the end nearest to the carbonyl group, so that the carbonyl carbon gets the lowest possible number.
3. The carbonyl group in a ketone is always located at a carbon atom that's within the chain, not at the end, so it will have a number associated with its position.
4. The suffix for ketones is "-one," which replaces the "-e" from the corresponding alkane name of the longest chain.
5. Combine the position number of the carbonyl group with the base name, placing the number in front of the base name. For example, if the carbonyl is on the second carbon of a four-carbon chain, the base name is "butanone" (butane + one), and it is written as "2-butanone."
6. If there are other substituents or groups attached to the main chain, name them as prefixes, and give them location numbers as well.

How do you name a ketone as a substituent?

When naming a ketone as a substituent in organic chemistry, you use the prefix "oxo-" to indicate the presence of a ketone group attached to the longest carbon chain, which is considered the parent compound. The ketone group is not included in the parent chain but is treated as a substituent.

To properly name it, you must identify the carbon to which the ketone is attached. You number the parent chain in such a way that the substituents get the lowest possible numbers. The position of the ketone group is indicated by a number corresponding to the carbon to which it is attached.

For example, if a ketone group is attached to the second carbon of a butane molecule, it would be named as "2-oxobutane." Here, "butane" represents the four-carbon parent chain, "oxo-" indicates the presence of a ketone group, and "2-" tells you that the ketone is attached to the second carbon atom. Remember that when the ketone is the highest priority functional group, it is named as part of the parent chain using the suffix "-one," but as a substituent, "oxo-" is the correct prefix.

How do you name a ketone using IUPAC?

To name a ketone using the International Union of Pure and Applied Chemistry (IUPAC) nomenclature, you follow these steps:

1. Identify the longest carbon chain that includes the carbonyl group (C=O). The carbonyl group is the functional group of ketones.
2. Number the carbon chain starting from the end nearest to the carbonyl group, so that the carbonyl carbon gets the lowest possible number.
3. Write the name of the alkane that corresponds to the longest chain, but replace the -e ending with -one to indicate the presence of a ketone. For example, if the longest chain has five carbons, the alkane would be pentane, and the ketone would be pentanone.
4. Indicate the position of the carbonyl group by placing the number of the carbonyl carbon in front of the ketone name. For example, if the carbonyl group is on the second carbon, the compound is named 2-pentanone.
5. If there are any substituents (additional groups or atoms attached to the main chain), name them as prefixes, and give their position numbers. List substituents in alphabetical order before the ketone name.

Example: 4-ethyl-2-pentanone indicates a ketone with an ethyl group on the fourth carbon and a carbonyl group on the second carbon.