Which of the following compounds would react with bromine water at room temperature in the dark?
Show the answer and explanation
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
Ethene (C2H4) has a double bond and reacts with bromine water to form 1,2-dibromoethane, decolorizing the orange/brown bromine solution. Ethane is an alkane and only reacts with bromine in the presence of UV light (substitution), not with bromine water at room temperature in the dark. Ethanol and chloroethane do not have a double bond and do not react with bromine water.
Example
Bubbling ethene through bromine water: the orange color disappears, forming a colorless solution.
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