Which of the following compounds will react with an aqueous solution of bromine at room temperature?
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Correct answer
B. Ethene
Principle or equation
Alkenes contain a carbon-carbon double bond, which undergoes addition reactions with bromine water, decolorizing it. Alkanes, alcohols, and haloalkanes do not react with bromine water under these conditions.
Why this answer is correct
Bromine water is a test for unsaturation. Ethene (C2H4) has a C=C double bond, so it adds bromine across the double bond, forming 1,2-dibromoethane and decolorizing the orange bromine solution. Ethane (C2H6) is saturated and does not react. Ethanol and chloroethane do not have double bonds and do not react with bromine water at room temperature.
Example
C2H4 + Br2 (aq) → C2H4Br2 (colorless)
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