Esters are formed by the condensation reaction between an alcohol and a carboxylic acid. This is known as esterification. In a condensation reaction, two molecules join and produce a larger molecule whilst eliminating a small molecule. During esterification this small molecule is water. Esters have characteristic smells and are insoluble in water.


\({\rightleftharpoons}\) (means a reversible reaction)

They have the functional group:

A hydrocarbon chain R1 is single-bonded to an oxygen which is single-bonded to a carbon. The carbon is double-bonded to a second oxygen, and single-bonded to a second hydrocarbon chain R2.

The functional group (-COO) is known as the ester link. The main use of esters is for flavourings and perfumes, however they can also be used in the chemicals industry as solvents.

Naming esters

To name an ester:

  1. change the name of the parent alcohol to end in –yl
  2. change the name of the parent acid to end in –oate
  3. alcohol name goes to the front, acid name to the back

For example:

\[Propanol + Ethanoic\,\,Acid \rightleftharpoons Propyl\,\, Ethanoate + Water \]

\[Methanoic\,\,Acid + Ethanol \rightleftharpoons Ethyl\,\,Methanoate + Water\]