The reacton begins with an attack on the electrophile, HBr, of the nucleophilic ¶ bond. Two electrons from the ¶ bond form a new α bond between the entering hydrogen and an alkene carbon, as shown by the curved arrow at the top of Figure 6.10. The carbocation intermediate that results is itself an electrophile, which can accept an electron pair from nucleophilic Br- ion to form a C-Br bond and yield a neutral addition product