Naming Ketones
(Chemical) Definition of Ketones:
Ketones are organic chemical compounds that include a -carbonyl group (i.e. an oxygen atom attached to a carbon atom by a double covalent bond) such that the carbon atom to which the -carbonyl group is attached is itself attached to two other carbon atoms - as opposed to one other carbon atom and one hydrogen atom, which the case for aldehydes
|
|
That is, ketones are a class or category of organic chemical compounds that include a carbon atom attached to both an oxygen atom (by a double covalent bond), and also to two other carbon atoms (by a single covalent bond in each case).
Bearing in mind that carbon atoms form a total of 4 single covalent bonds - or equivalent in combinations of double or triple bonds, a carbon atom attached to both an oxygen atom (by a double covalent bond) and also to two other carbon atoms (by a single covalent bond in each case) cannot be the first- or last - (which are equivalent positions) carbon atom in the chain of carbon atoms that form the organic molecule of which it is a part.
This position of the -carbonyl group (oxygen atom) attached to a carbon atom that is not the last carbon atom in a carbon-chain is important because it distinguishes ketones from a similar category of organic compounds, called aldehydes.
(In contrast to ketones, aldehydes include a -carbonyl group attached to the end-carbon in a carbon-chain.)
Ketone molecules can vary in size up to very long molecules most of which consist of carbon atoms attached to each other and also to hydrogen atoms. |
Names of Ketones in General
Ketones are named according to the same system as other organic compounds, with the suffix -one used to designate the presence in the molecule of a carbonyl group (that is, a carbon atom attached to an oxygen atom by via a double covalent bond) such that the carbon atom to which the oxygen atom is attached is not the last carbon atom in a chain or branch, but is always within (the middle of) a chain of carbon atoms. This may be easier to understand by looking at examples of the molecular structures of some simple ketones, as shown below:
As usual in organic chemistry, the first step to consider when working out the name of a ketone molecule is the number of carbon atoms forming the longest straight, i.e. unbranched, chain within the molecule. Having identified the longest unbranched carbon chain within the molecule in terms of the number of carbon atoms in the chain, the main stem of the name of the chemical is as per the system used for naming alkanes.
If the carbon atoms do not form a linear chain but include branches, the longest linear chain of carbon atoms within the molecule determines the base of the name of the compound, onto which is added information about the branches incl. their lengths in terms of the number of carbon atoms in each branch (i.e. methyl- usually indicates a branch consisting of just one carbon atom attached to the main chain, ethyl- indicates a branch of two carbon atoms in length, etc.) and their positions along the longest linear carbon chain (e.g. attached to the 2nd carbon, 3rd carbon, etc.). Branched ketones are therefore more complicated to name than linear ketones.
The simplest linear ketones are named and their structures drawn in the following table.
More complex ketone molecules follow afterwards.
Names and Structures of simple Linear Ketones - with the -carbonyl group attached to the 2nd carbon
Examples from the homologous series of linear ketones in which a -carbonyl group is attached to the second carbon atom: |
Note: Carbon atoms are counted from the right-side of molecules in the large table below but these structures could equally have been drawn the other way around, with carbon atoms counted from the left-side, i.e. the following two structures are equivalent and both represent the same structure of 2-butanone:
|
 |
2-butanone |
 |
Likewise, the following two representations are also equivalent ways of drawing the same structure of 2-butanone as those represented above: |
 |
|
 |
Therefore all four of the above representations of 2-butanone are equivalent. |
Number carbons in chain |
Name |
Simple Structure |
Other Names = Synonyns
(*Examples not complete lists) |
and simple formula |
showing bond types but not accurate bond angles |
 |
3 |
2-propanone (C3H6O) |
CH3COCH3 |
|
 |
- propan-2-one
- acetone
- dimethyl ketone
- methyl ketone
- dimethylketal
- ketone propane
- pyroacetic acid
- beta-Ketopropane
- dimethylformaldehyde
|
4 |
2-butanone (C4H8O) |
CH3CH2COCH3 |
|
 |
- butan-2-one
- methyl ethyl keyone
- methylethyl ketone
- ethyl methyl ketone
- methylethylketone
- methyl acetone
- oxobutane
- meetco
|
5 |
2-pentanone (C5H10O) |
CH3CH2CH2COCH3 |
|
 |
- pentan-2-one
- ethyl acetone
- ethylacetone
- methyl propyl ketone
- methylpropyl ketone
- methyl n-propyl ketone
- propyl methyl ketone
|
6 |
2-hexanone (C6H12O) |
CH3CH2CH2CH2COCH3 |
|
 |
- hexan-2-one
- hexanone-2
- butyl methyl ketone
- n-butyl methyl ketone
- propylacetone
- methyl butyl ketone
- methyl n-butyl ketone
- 2-hexanone methyl n-butyl ketone
- 2-oxohexane
|
7 |
2-heptanone (C7H14O) |
CH3CH2CH2CH2CH2COCH3 |
|
 |
- heptan-2-one
- methyl pentyl ketone
- methyl n-pentyl ketone
- butylacetone
- n-amyl methyl ketone
- amyl methyl ketone
- methyl n-amyl ketone
- n-pentyl methyl ketone
- methyl amyl ketone
- pentyl methyl ketone
- methyl n-pentyl ketone
- methyl-n-amylketone
- ketone C-7
|
8 |
2-octanone (C8H16O) |
CH3CH2CH2CH2CH2CH2COCH3 |
|
 |
- octan-2-one
- hexyl methyl ketone
- n-hexyl methyl ketone
- methyl hexyl ketone
- methyl n-hexyl ketone
- 2-Oxooctane
|
9 |
2-nonanone (C9H18O) |
CH3CH2CH2CH2CH2CH2CH2COCH3 |
|
 |
- nonan-2-one
- methyl heptyl ketone
- methyl n-heptyl ketone
- heptyl methyl ketone
- beta-nonanone
|
10 |
2-decanone (C10H20O) |
CH3CH2CH2CH2CH2CH2CH2CH2COCH3 |
 |
|
 |
- decan-2-one
- methyl octyl ketone
- methyl n-octyl ketone
- octyl methyl ketone
|
Names and Structures of simple Linear Ketones - with the -carbonyl group attached to the 3rd carbon
Examples from the homologous series of linear ketones in which a -carbonyl group is attached to the third carbon atom:
Number carbons in chain |
Name |
Simple Structure |
Other Names = Synonyns
(*Examples not complete lists) |
and simple formula |
showing bond types but not accurate bond angles |
|
5 |
3-pentanone (C5H10O) |
CH3CH2COCH2CH3 |
|
 |
- pentan-3-one
- pentanone-3
- diethyl ketone
- propione
- dimethylacetone
- methacetone
- metacetone
- ethyl ketone
- diethylcetone
- ethyl propionyl
|
6 |
3-hexanone (C6H12O) |
CH3CH2CH2COCH2CH3 |
|
 |
- hexan-3-one
- ethyl propyl ketone
- ethyl n-propyl ketone
- 3-oxohexane
|
7 |
3-heptanone (C7H14O) |
CH3CH2CH2CH2COCH2CH3 |
|
 |
- heptan-3-one
- butyl ethyl ketone
- n-butyl ethyl ketone
- ethyl butyl ketone
- ethyl n-butyl ketone
- ethylbutylcetone
- ethyl-n-butyl ketone
- etilbutilchetone
- eptan-3-one
|
8 |
3-octanone (C8H16O) |
CH3CH2CH2CH2CH2COCH2CH3 |
|
 |
- octan-3-one
- n-octanone-3
- amyl ethyl ketone
- ethyl pentyl ketone
- ethyl n-amyl ketone
- ethyl n-pentyl ketone
- ethyl n-amylketone
- 3-Oxooctane
|
9 |
3-nonanone (C9H18O) |
CH3CH2CH2CH2CH2CH2COCH2CH3 |
|
 |
- ethyl hexyl ketone
- n-hexyl ethyl ketone
- ethyl n-hexyl ketone
|
10 |
3-decanone (C10H20O) |
CH3CH2CH2CH2CH2CH2CH2COCH2CH3 |
|
|
 |
|
Why stop at ten carbon atoms (in the chain) ? It doesn't, there are more similar linear ketones. We stopped here due to page width.
Important Note: *The synonyms indicated for compounds listed above are just some examples of alternative names found online and believed to have been used to refer to the substance indicated. They have not all been verified and may include common (non-scientific) names, trade names specific to particular suppliers, and perhaps errors. The purpose of these lists is to give a general indication of the range of names by which ketones are known - both generally, and specifically.
Note:
This is one of many pages about types of organic compounds in our Organic Chemistry Section. Similar and related pages describe hydrocarbons, alkanes, haloalkanes, alkenes, alkynes, cycloalkanes, aromatic hydrocarbons (arenes), alcohols, esters, ethers, aldehydes, ketones, carboxylic acids, acid chlorides, acid anhydrides, azo dyes, amines, amides, nitriles, amino acids (chemistry), peptides, proteins (chemistry), polypeptides and others. If you need further information ask your chemistry tutor.
|
