AQA GCSE Chemistry · Organic chemistry · Triple only

Making esters

A carboxylic acid reacts with an alcohol, with an acid catalyst, to make an ester and water. Ethanoic acid and ethanol make ethyl ethanoate. Choose an acid and an alcohol to watch the reaction and see what the ester is used for.

Chemistry 8462: 4.7.2.3 Alcohols, 4.7.2.4 Carboxylic acids Separate chemistry only
Acid
Alcohol
Catalyst
Concentrated sulfuric acid (a few drops)
Conditions
Warm, in a water bath
Other product
Water
Note
The reaction is reversible, so not all of the acid and alcohol react.
Functional groups

Spot the family from the group

Carboxylic acid–COOHEthanoic acid, CH₃COOH. Names end in -oic acid.
Alcohol–OHEthanol, C₂H₅OH. Names end in -ol.
Ester–COO–Ethyl ethanoate, CH₃COOC₂H₅. Names end in -oate.

How to name an ester

The name has two parts. The first part comes from the alcohol: ethanol gives ethyl. The second part comes from the acid: ethanoic acid gives ethanoate. So ethanol + ethanoic acid → ethyl ethanoate.

AQA only requires you to name ethyl ethanoate. The other examples on this page help you see the pattern.

Uses

Esters you might have smelled

Esters are volatile: they evaporate easily, so their smell reaches your nose. Many smell sweet or fruity. This makes them useful as flavourings and in perfumes. Some are also good solvents.

In the lab

Making ethyl ethanoate

Method

  1. Put some ethanol and ethanoic acid in a boiling tube.
  2. Add a few drops of concentrated sulfuric acid as a catalyst.
  3. Warm the tube in a hot water bath for a few minutes. Ethanol is flammable, so there must be no naked flame nearby.
  4. Pour the mixture into sodium hydrogencarbonate solution. This neutralises leftover acid. The ester floats on top as an oily layer.
  5. Smell the ester carefully by wafting.

Why esters suit their uses

  • Flavourings: fruity smells and tastes, used in sweets and drinks.
  • Perfumes: pleasant smells, and volatile, so they evaporate from the skin and reach your nose.
  • Solvents: they dissolve substances such as nail varnish, glue and paint, then evaporate quickly.

Esters are flammable, and breathing in large amounts of solvent vapour is harmful. Use them in a well-ventilated room.

Unlimited practice

Name the ester

Correct: 0 · Streak: 0

Check understanding

Quick quiz

Exam practice

Exam-style questions

Ethanoic acid reacts with ethanol to produce an ester.

Name the ester, name the catalyst, and give the other product of the reaction.

[3 marks]
Show mark scheme
  1. Ethyl ethanoate (1)
  2. (Concentrated) sulfuric acid (1)
  3. Water (1)

Accept “an acid catalyst” only if the question does not ask for a name.

Esters are used in perfumes.

Give two properties of esters that make them suitable for this use.

[2 marks]
Show mark scheme
  1. Volatile / evaporate easily (1)
  2. Have a pleasant (sweet or fruity) smell (1)

Ethyl ethanoate has the formula CH₃COOC₂H₅.

Circle the functional group in a drawing of ethyl ethanoate and name the homologous series it belongs to. Give one use of ethyl ethanoate.

[3 marks]
Show mark scheme
  1. –COO– group identified (1)
  2. Esters (1)
  3. Solvent (e.g. in nail varnish remover or glue) or flavouring (1)
Stretch

An ester called methyl butanoate smells of apples. Name the alcohol and the carboxylic acid used to make it.

[2 marks]
Show mark scheme
  1. Methanol (1)
  2. Butanoic acid (1)

The first part of the name (methyl) comes from the alcohol. The -oate part comes from the acid.