The addition of HBr to unsymmetrical alkenes against the Markownikoff s rule is called peroxide effect or Anti Markownikoff s rule. According to this effect, “the negative part of the unsymmetrical attacking reagent attached to that carbon atom of the double bond of unsymmetrical alkene which bears the higher number of hydrogen atoms.” This reaction takes place in the presence of peroxide.
RecNotes Asked question March 16, 2021