Addition of HX to Alkenes Step 1 is the protonation of the double bond. The protonation step forms the most stable carbocation possible. In step 2,the nucleophile attacks the carbocation,forming an alkyl halide. HBr,HCI,and HI can be added through this reaction. Chapter8 5 Chapter 8 5 Addition of HX to Alkenes • Step 1 is the protonation of the double bond. • The protonation step forms the most stable carbocation possible. • In step 2, the nucleophile attacks the carbocation, forming an alkyl halide. • HBr, HCl, and HI can be added through this reaction