Radioisomerization and photoisomerization of liquid 2-butenes in the presence of sulfur compounds

The liquid phase radiolysis and photolysis of cis- and trans-2-butenes were studied in the presence of various additives. A very efficient isomerization of 2-butenes was achieved by the addition of thiols of low molecular weight (hydrogen sulfide, methyl and isopropyl mercaptans). In the absence of molecular oxygen, we have observed G values (trans-2-butene) of the order of 90 000. On the other hand, little or no isomerization occurred in the presence of carbon disulfide, sulfur hexafluoride, and tert-dodecylmercaptan. Although the majority of the additives have no effect on the 2-butene:hydrogen sulfide system, conjugated diolefins block the isomerization reaction. These diolefins disappear from the reaction mixture.