Question

Choose the correct statement when an alkene reacts with bromine in presence of $CC{l}_4$ :

• A. The color of solution changes from orange to blue
• B. The color of solution stays orange
• C. The color of solution changes from colourless to orange
• D. The color of solution changes from orange to colourless

Answer 1

The correct option is D The color of solution changes from orange to colourless

This is a confirmatory test of alkenes or the test of unsaturation.
When an alkene is mixed with bromine in $CC{l}_4$ its colour changes from orange to colorless. Bromine in $CC{l}_4$ is a orange brown coloured solution. When bromine reacts with alkene it forms dibromoalkane by addition reaction, due to which orange colour disappears.
Example: $R-C{H}_2=C{H}_2-R+B{r}_2\stackrel{CC{l}_4}{⟶}R-C{H}_{2}Br-C{H}_{2}Br-R$