Disclosed are processes for the conversion of isomerizable halogenated C2-C6 olefins from one geometric form to a more preferred geometric form. Preferred process aspects comprise converting C2-C6 olefin in a cis-form to a trans-form comprising exposing the cis-form of the compound, preferably contained in process stream, to conditions effective to convert at least about 50 percent, and even more preferably at least about 70 percent, of the cis-form compound to the trans-form compound. Preferably the catalyst comprises at least one Lewis acid metal fluoride.