bydrogen halides react with alkenes h CI Cl Sloy fast Carbocation(正碳离子) Addition reaction mechanism Ht Cr CI c—C SlOw fast Carbocation(正碳离子)Hydrogen halides react with alkenes  H + Cl - Carbocation (正 碳 离 子 ） H + Cl - H Cl Slow fast  C C C C H Cl sp 2 sp 3 H + Cl - H + Cl -   slow fast Addition Reaction Mechanism Carbocation (正 碳 离 子 ）