The pyrolysis reactions of dihalocyclopropanes and monohalocyclopropanes were carried out at 200–400° C. Bromo-substituted cyclopropanes were readily decomposed in this temperature range. In all cases, the pyrolysis products were ring-opened olefinic hydrocarbons. As for the monohalocyclopropanes, the reactions proceed in a stereospecific manner. The possible mechanism was discussed in terms of the requirements of the ...