The electrophilic addition reaction of HBr to propene involves the following steps:Step 1: Protonation of the alkeneIn the first step, the alkene propene acts as a nucleophile and attacks the electrophilic hydrogen atom of HBr. This leads to the formation of a carbocation and a bromide ion Br- . The double bond between the carbon atoms in propene is broken, and one of the carbon atoms forms a bond with the hydrogen atom from HBr.Propene + HBr Carbocation + Br-Step 2: Nucleophilic attack by bromide ionIn the second step, the bromide ion Br- acts as a nucleophile and attacks the carbocation formed in the first step. This leads to the formation of the final product, 2-bromopropane.Carbocation + Br- 2-bromopropaneThe overall reaction mechanism can be represented as:Propene + HBr 2-bromopropaneNow, let's discuss why this reaction follows Markovnikov's rule. Markovnikov's rule states that in the addition of a polar reagent like HBr to an alkene, the hydrogen atom will attach to the carbon with the greater number of hydrogen atoms, while the other part of the reagent Br- will attach to the carbon with fewer hydrogen atoms.In the case of propene, the double bond is between the first and second carbon atoms. According to Markovnikov's rule, the hydrogen atom from HBr will attach to the second carbon atom which has two hydrogen atoms , and the bromine atom will attach to the first carbon atom which has only one hydrogen atom . This leads to the formation of 2-bromopropane.The reason behind Markovnikov's rule is the stability of the carbocation intermediate formed during the reaction. When the hydrogen atom attaches to the carbon with more hydrogen atoms, the resulting carbocation is more stable due to the inductive effect and hyperconjugation. In the case of propene, the secondary carbocation formed is more stable than a primary carbocation, which would be formed if the hydrogen atom attached to the first carbon atom. This stability drives the reaction towards the formation of 2-bromopropane, following Markovnikov's rule.