The electrophilic addition reaction of propene with hydrogen halides HX involves a two-step mechanism. Here, I will describe the mechanism using HBr as an example, but the mechanism is similar for other hydrogen halides HCl, HI, etc. .Step 1: Protonation of the alkene formation of a carbocation In the first step, the alkene propene acts as a nucleophile and attacks the electrophilic hydrogen atom of the hydrogen halide HBr . This leads to the breaking of the H-Br bond, with the electrons from the bond moving to the bromine atom. As a result, a carbocation positively charged carbon intermediate is formed, and a bromide ion Br- is generated. In the case of propene, the carbocation is formed on the secondary carbon, which is more stable due to hyperconjugation.Propene + HBr -> [CH3-CH + -CH3] + Br-Step 2: Attack of the nucleophile bromide ion on the carbocationIn 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 product, 2-bromopropane.[CH3-CH + -CH3] + Br- -> CH3-CH Br -CH3Overall reaction:Propene + HBr -> 2-bromopropaneIn summary, the electrophilic addition reaction of propene with hydrogen halides HX involves the protonation of the alkene to form a carbocation intermediate, followed by the attack of the halide ion on the carbocation to generate the final product.