6.3.1

Acids & Esters (A2 Only)

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Carboxylic Acids

Carboxylic acids have some useful reactions, among them neutralisation reactions and esterification.

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Structure

  • Above is a molecule containing -COOH, the carboxylic acid functional group. This example is called propanoic acid.
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Acidic properties

  • Carboxylic acids are weak acids.
    • This means they only partially ionise in water.
  • They will react with carbonates to produce carbon dioxide.
    • This can be used as a test for carboxylic acids.
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Esterification

  • Carboxylic acids will react with alcohols.
  • This reaction is called esterification. It produces an ester.
    • Usually, you would use sulfuric acid as a catalyst for this reaction.
  • You don't need the mechanism for this, but the ester group is shown on the next slide.
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Structure of ester

  • The ester formed from the reaction between an alcohol and a carboxylic acid will contain the ester functional group, R-COO-R, as shown above.

Esters

Esters are very useful compounds and also occur in nature.

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Uses of esters

  • Examples of uses of esters are:
    • Plasticisers.
    • Solvents (ethyl ethanoate).
    • Perfumes.
    • Food flavourings (ethyl butrate, pineapple).
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Biodiesel

  • Biodiesel is made up of methyl esters of long chain carboxylic acids.
  • The long-chained carboxylic acids are reacted with methanol to make the esters.
  • Biodiesel is made by reacting vegetable oils with methanol in the presence of a catalyst.

Natural Esters

The ester functional group is widely used in nature.

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Fats and oils

  • Vegetable oils and animal fats are esters of propane-1,2,3-triol.
    • Biologists would call this triol, glycerol.
  • At room temperature, vegetable fats are liquids (oils) but animal fats are usually solid.
    • This is because vegetable oils are usually unsaturated and have weaker van der Waals forces.
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Soaps

  • You can hydrolyse natural esters to give soaps and glycerol.
    • Glycerol is the common name for propane-1,2,3-triol.
    • Soaps are just salts of long chain carboxylic acids.

Jump to other topics

1Physical Chemistry

2Physical Chemistry 2 (A2 Only)

3Inorganic Chemistry

4Inorganic Chemistry 2 (A2 Only)

5Organic Chemistry 1

6Organic Chemistry 2 (A2 Only)

6.1Optical Isomerism (A2 Only)

6.2Aldehydes & Ketones (A2 Only)

6.3Carboxylic Acids & Esters (A2 Only)

6.4Aromatic Chemistry (A2 Only)

6.5Amines (A2 Only)

6.6Polymers (A2 Only)

6.7Biological Organic (A2 Only)

6.8Organic Synthesis (A2 Only)

6.9NMR Spectroscopy (A2 Only)

6.10Chromatography (A2 Only)

6.11A-A* (AO3/4) - Organic 2

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