Formation of Halohydrins (Addition of Hal2 and H2O to Alkenes)

Step 1: Electrophilic Addition

This flow of electrons forms the cyclic bromonium ion.  We have already seen this ion as the intermediate in the addition of Br2 to alkenes to form a trans 1,2-dibromide.  However, when used as a solvent, water will act as a nucleophile. Click on an electrophilic atom in the structure if the starting material shown above.

Step 1 - Step 2 - Step 3
 

Intermediate:

A cyclic bromonium ion

Overall Reaction