5.6.2

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Test yourself

Testing for Alkenes

We can test a solution to see if the alkene function group is present.

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The test

  • Add bromine water to the solution.
    • If an alkene is present, the solution will lose its orange colour and become colourless.
    • If an alkene is not present, it will NOT decolourise and the solution remains orange.
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How the test works

  • The test works because:
    • If the alkene is present, it can undergo an addition reaction with the bromine.
    • This removes the bromine (in the bromine water) and forms a halogenoalkane - so the colour is lost.
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Bromine water

  • As a quick note, bromine water is just water with a small amount of bromine dissolved in it.
    • Bromine water is what colours the solution orange until it has reacted with the alkene.

Testing for Carboxylic Acids

We can test to see if a carboxylic acid is present in a solution.

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The test

  • Firstly we must react the carboxylic acid with sodium carbonates.
    • The reaction with the carbonate ions should form a salt + CO2 + H2O
  • We can then test for the CO2 produced using limewater.
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Limewater

  • Limewater is a clear solution but it is turned cloudy if CO2 is present.
    • This means we must pump the gas, produced from the reaction between the sample and the carbonate, into limewater.
      • If limewater turns cloudy: carboxylic acid is present in the initial solution.
      • If limewater stays clear: carboxylic acid is NOT present in the initial solution.

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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