Question

How would you convert Ethene to $1,2-dibromoethane$?

Answer 1

Being unsaturated, Ethene$\left(C_2{H}_4\right)$ undergoes an addition reaction. During this process, the double bond is converted to a single bond through ionic mechanism.

When a halogen like Bromine$\left(B{r}_2\right)$ is added, Ethene$\left(C_2{H}_4\right)$ decolorizes forming $1,2-dibromoethane$. This decolorization reaction also serves as a test to determine the presence of Ethene$\left(C_2{H}_4\right)$.

Reaction Equation:

$\underset{\left(\mathrm{Ethene}\right)}{{\mathrm{C}}_2{\mathrm{H}}_4\left(\mathrm{g}\right)}+\underset{\left(\mathrm{Bromine}\right)}{{\mathrm{Br}}_2\left(\mathrm{g}\right)}\to \underset{(1,2-\mathrm{dibromoethane})}{{\mathrm{CH}}_2\mathrm{Br}-{\mathrm{CH}}_2\mathrm{Br}\left(\mathrm{g}\right)}$

We can easily see the evidence for this addition of bromine to an alkene. Bromine is red-orange in color. It reacts with alkenes to give a colorless product. If the bromine color disappears when $B{r}_2$ is added to the compound, we conclude that the compound is unsaturated.