Electrophilic addition of hydrogen halides

Hydrogen halides (HCl, HBr, HI)  adds to alkenes to yield alkyl halides.  This addition is regioselective in accordance with Markovnikov's rule, "the proton from the hydrogen halide attaches itself to the less substituted carbon.

Step 1. Proton addition acordin to Markovnikov's rule to form a carbocation
Step 2. Nucleophilic addition by halide ion


Addition of HCl to 2-Metylbut-2-ene