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

Introduction

Alkenes react with halogens (Cl2, Br2 and I2) in aqueous solution (or in the presence of water) to form 2-haloalcohols or "halohydrins".  The reaction takes place with anti-addition.  In the case of a cyclic alkene, the resulting halohydrin has the halogen and hydroxyl group trans to one another.  This mechanism is illustrated by the addition of bromine and water across the carbon-carbon double bond of cyclohexane to give trans-2-bromocyclohexanol.

Product:

trans-2-bromocyclohexanol