What are Esters? (Edexcel IGCSE Chemistry (Modular)): Revision Note

Esters

Making esters

• Alcohols and carboxylic acids react to make esters in esterification reactions

• Esters are compounds with the functional group R-COO-R

  

• Esters are sweet-smelling oily liquids used in food flavourings and perfumes

• Ethanoic acid will react with ethanol in the presence of concentrated sulfuric acid (catalyst) to form the ester, ethyl ethanoate:

CH₃COOH + C₂H₅OH → CH₃COOC₂H₅ + H₂O

Diagram showing the formation of ethyl ethanoate

During this esterification reaction, a molecule of water is also produced

Naming Esters

• An ester is made from an alcohol and carboxylic acid

• The first part of the name indicates the length of the carbon chain in the alcohol, and it ends with the letters ‘- yl’

• The second part of the name indicates the length of the carbon chain in the carboxylic acid, and it ends with the letters ‘- oate’

  • E.g. The ester formed from pentanol and butanoic acid is called pentyl butanoate

Diagram showing the origin of each carbon chain in ester

• Some examples of common esters:

Examples of Esters Table