The test for unsaturated compounds
4 marks · NormalState what is meant by an unsaturated compound.
Describe a chemical test to distinguish between hexane and hex-1-ene.
Predict and state the result for each compound.
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(a) A compound that contains at least one carbon–carbon double bond (C=C); not all bonds are single.
(b) Add bromine water to separate samples of hexane and hex-1-ene and shake. Observe the colour change.
(c) Hexane: bromine water stays orange; hex-1-ene: bromine water is decolourised (goes colourless).
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Marking points
B1 (a) · 1 mark · A compound containing a C=C double bond / not all bonds are single.
B2 (b) · 1 mark · Describes adding bromine water to both compounds.
B3 (b) · 1 mark · States to shake and observe colour change.
B4 (c) · 1 mark · Correct results for each: hexane – stays orange; hex-1-ene – decolourises bromine water.
Worked solution
(a) An unsaturated compound contains a carbon–carbon double bond.
(b) Add bromine water to samples of each compound and shake; observe the colour change.
(c) Hexane: bromine water stays orange. Hex-1-ene: bromine water is decolourised.