91Ó°ÊÓ

The most common type of reaction shown by alkene is the addition reaction to the C=C double bond.

In this reaction, hydrogen halide is added to the multiple bond system (C=C) and one π-bond is converted into two sigma bonds, which means the degree of unsaturation decreases and produces an alkyl halide as a product of the addition reaction.

The mechanism of the reaction involves two-step:

In the first step of the reaction, pi-electrons of alkene act as a nucleophile and are attracted to the partially positively charged hydrogen of HX (X = Cl, Br, I) to form the carbocation.

In the second step of the reaction, Bromine reacts with positively charged carbocation to give the desired product as shown below:

$\mathrm{HBr}$Addition of $\mathrm{HBr}.$

The structure of two different alkenes represents the given carbocation intermediate is: