Naming Ketones - Online Tutor, Practice Problems & Exam Prep

Ketones are carbonyl compounds with a carbonyl carbon connected to two carbon atoms. Their naming follows similar rules to alcohols, changing the 'e' ending to '-one' and indicating the carbonyl group's location. Common names exist for specific ketones like acetone, acetophenone, and benzophenone, while others are named by listing the two alkyl groups alphabetically followed by "ketone." Understanding these naming conventions is essential for identifying and classifying ketones in organic chemistry.

IUPAC Rules for Naming Ketones Concept 1

Now recall that ketones possess a carbonyl carbon connected to two carbon atoms. Here, the set of rules for naming ketones is similar to those used for naming alcohols. However, the modifier, the ending of 'e' is changed to 'one'. 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 1

Here it says, provide the formal name for the ketone shown. Now to do that, we're going to use the following steps. Step 1 is to find the longest carbon chain, which represents our parent chain, and assign a name according to the prefixes and the modifier. The parent chain should include the carbonyl group. So remember, your carbonyl carbon or carbonyl group is this, C double bond O, and have a greater number of carbons. If there is a tie between the longest chains, choose the chain with more substituents. If we take a look here, our longest carbon chain would be this portion here. Now assign a name to all substituents for step 2. Our substituent here would be this carbon that's branching off of the main chain, which would be a methyl group. Step 3. Start numbering the chain from the end closest to the carbonyl carbon. So we'd have to start numbering from this end. 1, 2, 3, 4, 5, 6, 7, 8. If a tie, the number from the end closest to the next substituent. If still a tie, number in alphabetical order in terms of the substituents. And then here, assign a location to the carbonyl carbon. The carbonyl carbon is on carbon number 2. Alright. And then we repeat steps 4 to 6, 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 to 6. 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 2, 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. 3,3-dichloro-5-hexanone
• B. 4,4-dichloro-5-hexanone
• C. 4,4-dichloro-2-hexanone
• D. 3,3-dichloro-2-hexanone

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

• A.
• B.
• C.
• D.

Provide the systematic name for the following cyclic ketone. 

• A. 1-bromo-3-cyclohexanone
• B. 3-bromocyclohexone
• C. 3-bromocyclohexanone
• D. 1-bromo-3-cyclohexone

Common Naming of Ketones Concept 2

Now when it comes to common naming, we're going to say that certain ketones have unique names given before the IUPAC naming system was developed. Now the unique ones apply to these three structures here. In the first one, we have our carbonyl group, and it's connected to 2 methyl groups, 1 on each side. It is a ketone, and usually, we change the e ending of our alkane structure to -one to reflect the ketone. Here, this becomes acetone. The next one, we have a carbonyl connected to 1 benzene ring on the left and this methyl group here on the right. Here, we're going to say that this is called acetophenone. Phenone because we're dealing with a phenyl ring. Remember, phenyl implies that we're dealing with a benzene ring. So this structure here. And then in this one, we have a carbonyl group with 2 benzene rings attached to it. This is known as Benzophenone. One of the benzene rings gives us the first part of the name benzo, and then the other benzene ring gives us the phenone at the end. Now here we're going to say that for the rest of the ketones, the common name consists of 2 alkyl groups, names followed by ketone. So the naming convention would be substituent 1, substituent 2, listed alphabetically, and then we end the name with ketone. So this is the rule we're going to apply when it comes to the common names of several types of ketones. But remember, these three particular ones have unique names that were developed before IUPAC naming systems were ever developed.

Naming Ketones Example 2

In this example question it says, provide a common name for the ketone shown. Alright. So here goes our ketone structure. In step 1, we have to identify the 2 alkyl groups connected to the carbonyl carbon. Remember, your carbonyl carbon is just a carbon double bonded to the oxygen. Connected to it is this alkyl group, which is one carbon, that's a methyl group, and then we have this carbon chain here. It consists of 3 carbon atoms. 1, 2, 3. So that would be propyl. So we've identified the 2 alkyl groups connected to my carbonyl carbon.

Step 2, name the alkyl groups alphabetically as substituents. Kind of jumped the gun here, we have already identified them as methyl and propyl. Now if they are identical alkyl groups, we use a numerical prefix di. So if they both were methyl groups, we'd say dimethyl. If they both were propyl groups, we'd say dipropyl.

Step 3, we end name of the compound with ketone, and write the names with spaces. So alphabetically, m comes before p, so this would be methyl propyl ketone. So its common name will be methylpropylketone.

Give common name for following ketone.

• A. sec-butyl ethyl ketone
• B. sec-butyl propyl ketone
• C. ethyl sec-butyl ketone
• D. propyl sec-butyl ketone

Provide common name for given ketone.

• A. p-isopropyl acetophenone ketone
• B. 4-isopropyl acetophenone
• C. p-isobutyl ketone
• D. 4-isobutyl acetophenone

Here’s what students ask on this topic:

What are the rules for naming ketones according to IUPAC nomenclature?

In IUPAC nomenclature, ketones are named by identifying the longest carbon chain that includes the carbonyl group. The suffix '-e' of the parent alkane is replaced with '-one'. The position of the carbonyl group is indicated by the lowest possible number. For example, in pentan-2-one, the carbonyl group is on the second carbon of a five-carbon chain. Additionally, any substituents are named and their positions are indicated. The general formula for naming ketones is: [position of carbonyl]-[parent chain]-one.

How do you name ketones with common names?

Common names for ketones are often derived from the names of the alkyl groups attached to the carbonyl carbon, followed by the word 'ketone'. For example, if the carbonyl group is attached to a methyl group and an ethyl group, the ketone is called methyl ethyl ketone. Some ketones have unique common names, such as acetone (propanone), acetophenone (1-phenylethanone), and benzophenone (diphenyl ketone). These names were established before the IUPAC system and are still widely used.

What is the difference between acetone, acetophenone, and benzophenone?

Acetone, acetophenone, and benzophenone are specific ketones with unique common names. Acetone (propanone) has a carbonyl group attached to two methyl groups. Acetophenone (1-phenylethanone) has a carbonyl group attached to a phenyl group and a methyl group. Benzophenone (diphenyl ketone) has a carbonyl group attached to two phenyl groups. These names were established before the IUPAC system and are still commonly used in both academic and industrial settings.

How do you determine the position of the carbonyl group in a ketone?

To determine the position of the carbonyl group in a ketone, identify the longest carbon chain that includes the carbonyl carbon. Number the chain from the end nearest to the carbonyl group to give the carbonyl carbon the lowest possible number. The position of the carbonyl group is then indicated by this number in the ketone's name. For example, in butan-2-one, the carbonyl group is on the second carbon of a four-carbon chain.

What are the key differences between naming ketones and alcohols?

While naming ketones and alcohols follows similar rules, there are key differences. For ketones, the suffix '-e' of the parent alkane is replaced with '-one', and the position of the carbonyl group is indicated by a number. For alcohols, the suffix '-e' is replaced with '-ol', and the position of the hydroxyl group is indicated by a number. Additionally, ketones have a carbonyl group (C=O) while alcohols have a hydroxyl group (OH).