The effect of electron-withdrawing groups on the ring opening of benzenium ions has been investigated by kinetics, equilibrium studies, and product analysis. The use of SnXl (X= Br or C1) compounds as highly ionizing solvents and as conveying agents of the X-nucleophile works quite well. 1, 2-Dihalo-3-(4-methoxyphenyl) propanes (2; X= Br or C1) and 1, 3-dihalo- 2-(4-methoxyphenyl) propanes (3; X= Br or C1) equilibrate at 100 “C in SnX'((X'= Br or C1) ...