The invention is a process for preparing a 2-halo-1-alkene comprising contacting a hydrocarbon stream with a hydrogen halide, in the presence of water and an effective amount of a catalyst, at a temperature between about 100.degree. C. and about 400.degree. C., wherein; the hydrocarbon stream comprises a 1,2-diene, a terminal acetylene or mixtures thereof, represented by the formulas CH.sub.2 .dbd.C.dbd.CH--R or CH.tbd.C--CH.sub.2 --R wherein R is hydrogen, alkyl, cycloalkyl or aryl and may be substituted or unsubstituted; the water is present in an amount of between about 1,000 and 100,000 parts per million by weight; and the catalyst comprises carbon, silica alumina, aluminosilicates, silica gel, silica, silica magnesia, silicalite, group IIIA, IIIB, IVA, IVB or V metal oxides or rare earth oxides.