'111e preferciitiul rcplaceiimit uf iotliiie in 3-iodoperitafluoropropeiie and i~ i%-clilort~.: i- iodot~~ ra~ luoru~ i apeiie by reactiiJl1 with chlorine and bromiue and with chloride and bromide ions is described. Ionic aiid free radical type reaction mechaiiisnlr wliich involve initial reagent attack at the double bond rather thnn at the allylic carbon atom are proposed for these reactions. The reactions with lialidc ioil are shown to be reversible. Treatment of ...