Abstract: Bromine chloride is contacted with a normally unreactive olefin such as 1,2-di, tri- or tetrahalo- ethylene or 1,2-di, tri- or tetraphenyl ethylene or 1-halo-2-phenyl ethylene or 1-halo-2-phenyl ethylene carrying in addition, one or more other halogen or phenyl substituents on the carbons of the double bond in a two-phase, aqueous-organic reaction medium containing a bromide salt dissolved in the aqueous phase to produce the dibrominated adduct of the olefin. By the process of the invention, tetrachloroethylene was brominated to give a 77% yield of 1,2-dibromotetrachloroethane.