Download Preparation of an ester

Preparation of an ester
Making an ester
Alcohols react with carboxylic acids to make esters.
The reaction is an equilibrium reaction.
Alcohol + carboxylic acid
ester + water
The yield can be increased by removing water as it is
formed. The reaction is catalysed by H+. A few drops
of concentrated sulfuric acid will provide the H+ while
also removing water.
A water bath will also speed up the reaction.
Take about 1–2 mL of ethanol in a test tube…
… and add 1 mL of pure ethanoic acid…
… followed by a few drops of concentrated sulfuric
acid.
Warm in a water
bath.
Take about 20 mL of sodium carbonate solution in a
beaker and pour the contents of the test tube in,
little at a time.
The sodium carbonate
reacts with the
unreacted acid, producing
carbon dioxide gas.
Smell the beaker. The
ester has quite a
different odour from the
parent acid and alcohol.
When the reaction has
ceased, pour the contents
of the beaker into a test
tube.
Low mass alcohols and
acids are miscible in water
due to hydrogen bonding,
but esters, which cannot
hydrogen bond, are not
miscible in water.
Esters also have low
boiling points, so most of
this ester has already
boiled off.