Why is Br_2 an electrophile?

1 Answer
Apr 15, 2016

Because the Br-Br bond is polarizable.

Explanation:

The halogen molecules have a large, polarizable electron cloud that (so we assume) can be distorted. ""^(delta+)X-X^(delta-) representations are very common, and these explain the reaction of the halogens with electron rich olefin species.

Interhalogen species, say I-Br can also undergo electrophilic substitution. The iodine end of the molecule is more polarizable. The bromine is more electronegative. With an unsymmetrical alkene, say propylene, that reacts with 1 equiv I-Br, which alkyl halides would you predict you would get?