CAIE A-Level Chemistry 14.2.3 Bromine-Water Test for Alkenes

Practise using aqueous bromine to test for a carbon–carbon double bond and reporting the observed colour change.

Exam points

add aqueous bromine at room temperature without ultraviolet light when testing an unknown compound
state that orange or brown bromine water is decolourised to colourless when C=C reacts
link the observation to addition across C=C while recognising that the test alone does not locate the bond

[Maximum number: 2]

$4 \vec{P}, Q$ and R all have the molecular formula $\mathrm{C}_{3} \mathrm{H}_{6} \mathrm{O}$ . They are all structural isomers of each other.
P and Q each contain an oxygen atom bonded directly to a carbon atom that is $\mathrm{sp}^{2}$ hybridised. R contains an oxygen atom bonded directly to a carbon atom that is $\mathrm{sp}^{3}$ hybridised.

R contains two different functional groups, one of which is an alkene group. R reacts with cold, dilute, acidified manganate(VII) ions to form propane-1,2,3-triol.

propane-1,2,3-triol

State the type of reaction and what you would observe when R reacts with bromine water.

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14.2.3—Of aq. bromine to show the presence of a C=C question 1