Chemistry with Mastering Chemistry: An Introduction to Organic, Inorganic and Physical Chemistry
Chemistry³: Introducing inorganic, organic and physical chemistry
Organic Chemistry by Clayden, Greeves, Warren & Wothers


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Naming Esters

Definition of Esters:

Esters are organic chemical compounds whose structure has the general form:

general molecular structure of an ester (class of organic compounds)

where the symbols "R1" and "R2" represent organic radicals, usually carbon chains.


In the case of esters, "R1" and "R2" are often carbon chains that may be either linear or branched and may also have other functional groups attached.
"R2" is not a hydrogen atom because if it were, the molecule would be a carboxylic acid rather than an ester.

The simplest esters to describe are those where both R1 and R2 are "an alkane less the hydrogen atom at the end of the chain", and hence where the hydrogen atom at the end of the corresponding alkane is replaced by the carbon or oxygen atom to which that "R" (so, R1 or R2 in the diagram above) is attached.

R1 and R2 are not necessarily the same (hence the "1" and "2" to distinguish them in the general definition of an ester).
However, they may be the same.

Names of Esters in General

Esters are named according to the standard system of naming organic compunds. As true for other types of organic compounds, there are also some non-standard names for esters in common usage. Some of the alternative names used for the simple esters shown in the tables of examples on this page are listed in the column under the header "synonyms".

The standard system for naming esters uses the suffix -oate to indicate that a molecule is an ester.
The two organic radicals (which are often carbon chains) labelled "R1" and "R2" in the diagram at the top of this page are also identified in the name of the compound, or molecule drawn-out to represent the compound.

This may be explained using a diagram of the simple example of ethyl propanoate:

This shows that esters consist of two parts (often carbon chains), as labelled "R1" and "R2" at the top of this page.


When working-out the name of an ester given its molecular structure the first steps are:

  1. Recognise that the molecule is an ester because it has the general form:
  2. Identify the parts labelled "R1" and "R2".
    To do this recall the standard system of labelling carbon chains as used for alkanes.
    Also take care to distinguish "R1" and "R2" by noticing which "R" the oxygen atom is attached to by a double bond.
    Note that "R1" and "R2" may be linear charbon chains (which are simpler to name) or they may be branched, and they may even have other functional groups (e.g. halogens, see haloalkanes) attached as well.


Familiarity with naming esters and, conversely, with drawing the molecular structures of esters given their names, comes with experience. It is helpful to begin by viewing a series of simple examples in order to recognise patterns in the process of naming esters that can then be applied to similar and more complex cases.

Some of the simplest esters are named and their structures drawn in the following tables:

 

Names and Structures of simple Linear Esters
in which R2 = CH3, which is known as a "-methyl group"

The homologous series of linear esters that include a -methyl group attached (via a single covalent bond) to the oxygen atom in the chain of the ester molecule. This description is easier to follow in conjunction with viewing the molecular structures in the table:

Name
Simple Structure

Other Names = Synonyns
(*Examples not complete lists)

and simple formula

showing bond types but not accurate bond angles

1

methyl formate
(C2H4O2)

molecular structure of methyl formate

2

methyl ethanoate
(C3H6O2)

molecular structure of methyl ethanoate

3

methyl propanoate
(C4H8O2)

molecular structure of methyl propanoate

4

methyl butanoate
(C5H10O2)

molecular structure of methyl butanoate

5

methyl pentanoate
(C6H12O2)

molecular structure of methyl pentanoate

6

methyl hexanoate
(C7H14O2)

molecular structure of methyl hexanoate

Names and Structures of simple Linear Esters
in which R2 = CH2CH3, which is known as an "-ethyl group"

The homologous series of linear esters that include an -ethyl group attached (via a single covalent bond) to the oxygen atom in the chain of the ester molecule. This description is easier to follow in conjunction with viewing the molecular structures in the table:

Name
Simple Structure

Other Names = Synonyns
(*Examples not complete lists)

and simple formula

showing bond types but not accurate bond angles

1

ethyl formate
(C3H6O2)

molecular structure of ethyl formate

2

ethyl ethanoate
(C4H8O2)

molecular structure of ethyl ethanoate

3

ethyl propanoate
(C5H10O2)

molecular structure of ethyl propanoate

4

ethyl butanoate
(C6H12O2)

molecular structure of ethyl butanoate

5

ethyl pentanoate
(C7146O2)

molecular structure of ethyl pentanoate

6

ethyl hexanoate
(C8H16O2)

molecular structure of ethyl hexanoate

Names and Structures of simple Linear Esters
in which R2 = CH2CH2CH3, which is known as an "-propyl group"

The homologous series of linear esters that include an -propyl group attached (via a single covalent bond) to the oxygen atom in the chain of the ester molecule. This description is easier to follow in conjunction with viewing the molecular structures in the table:

Name
Simple Structure

Other Names = Synonyns
(*Examples not complete lists)

and simple formula

showing bond types but not accurate bond angles

1

propyl formate
(C4H8O2)

molecular structure of propyl formate

2

propyl ethanoate
(C5H10O2)

molecular structure of propyl ethanoate

3

propyl propanoate
(C6H12O2)

molecular structure of propyl propanoate

4

propyl butanoate
(C7H14O2)

molecular structure of propyl butanoate

5

propyl pentanoate
(C8H16O2)

molecular structure of propyl

6

propyl hexanoate
(C9H18O2)

molecular structure of propyl hexanoate

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