Theoretical Considerations Concerning the Reactions Between Ethylene and the Halogens and Their Products

Ethylene may react with a halogen by a substitution reaction to give a vinyl halide and hydrogen halide, or the halogen may add to the double bond to give 1,2-dihalo-ethane or rearrange and give ethylidene halide. It is found that the symmetrical addition is favored in the case of each halogen. 1,2-dihalo-ethane, or the corresponding ethylidene compound may decompose to give ethylene and the halogen, or the vinyl halide and hydrogen halide. It is found that ethylene formation is favored in the bromine and iodine derivatives, whereas, in agreement with experiment, vinyl chloride and HCl would be produced from either 1,2-dichlor-ethane or ethylidene chloride. In most of the reactions considered mechanisms involving free radicals are slightly more probable than the corresponding unimolecular or bimolecular reactions.