The reaction of propene with iodine bromide

Abstract

Iodobromination of propene gives a mixture (c. 60 : 40) of 2-bromo-1-iodopropane and 1-bromo-2-iodopropane. This mixture of kinetic control converts into an equilibrium (c. 70 : 30) mixture with heat. The addition to the double bond is postulated to occur through a bridged iodonium ion rather than through a simple carbocation, and hence Markownikoff's rule need not apply to this system.