The mode of addition of Unsymmetrical reagents to unsymmetrical olefin derivatives has been the subject of a great deal of investigation and there has been much speculation concerning the factors influencing the course of the addition.'In general, for the simplest case, RCH= CH2, normal addition has been found to obey Markownikoff's rule if R is a group which is also o, p-orienting when attached to the benzene ring.
