Basic Organic Nomenclature

Ketones

Suffix:    -one

Prefix:    oxo

Ketones are the first of a number of compounds containing the carbonyl group ( C=O ).  This double bonded carbon - oxygen pair is found in; aldehydes, amides, acid anhydrides, acyl halides, carboxylic acids, esters, and ketones. The only difference between these compounds is the nature of the two groups attached to the carbonyl carbon atom. In the case of a ketone this will be two alkyl groups, therefore the carbonyl group will appear in the middle of a chain, or in a ring.

When a keto group is the highest priority functional group present in the molecule, it is names as an alkanone (note, the -e is dropped), or an alkyl alkyl ketone. The numbering scheme used will be the one that gives the carbonyl carbon atom the lowest possible number. Other functional groups are located by this numbering scheme. When the keto group is the only functional group present the number locating it is place in front of the root name (i.e. 2-propanone). When other functional groups such as multiple bonds are present, the number locating the keto group is placed before the -one (i.e. 4-penten-2-one). There are a number of compounds which were named before IUPAC developed the standardized nomenclature rules. Many of these compounds are still referred to by these common names. The common names for the some of the more common compounds will be included (underlined in bold) and should be memorized.

Examples naming simple ketones:

Compound Name
Line Drawing
3D Model
2-propanone *
or
dimethyl ketone
or
acetone
2-butanone
or
ethyl methyl ketone
 2-pentanone
or
methyl propyl ketone
3-pentanone
or diethyl ketone
cyclobutanone
2,4-pentadione **

* note: the 2 in 2-propanone is redundant as the carbonyl must be located at carbon 2 for it to be a ketone.
** note: the -a as added with the di- prefix of the dione.

Examples naming more complex ketones:

Compound Name
Line Drawing
4,4-dimethyl-2-pentanone
4-penten-2-one
 4-amino-3-isopropyl-2-hexanone
5-hydroxy-2-cyclohexenone

Ketones as Substituents:

In more complex molecules with higher priority functional groups, the keto group is named as an oxo substituent. It is located by numbering the longest chain of carbons (according to the higher priority functional group) and locating the carbon atom of the carbonyl group by this numbering scheme. Examples of these structures will be given in the subsequent pages.
 

Tutorial Quiz: Ketones

Next Page: Aldehydes

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