How do alkenes react with chlorine?
Via electrophilic addition.
As the non polar chlorine molecule approaches the alkene double bond a dipole is induced in the halogen molecule. The pi bond in the alkene double bond breaks and forms a bond to the delta positive Cl atom, causing the Cl - Cl Bond to break a generating a chloride ion. Carbocation results and a lone pair of electrons o; 5he choride ion forms a dative Bon£ with the carbocation.