Free-radical additions of thiols and of hydrogen sulfide to olefinic compounds have been studied extensively during the past twenty-five years,'but additions to acetylenic compounds have received far less attention. The “thermal” addition of p-thiocresol to phenylacetylene to give a quantitative yield of a mixture of the cis and trans isomers of p-tolyl P-styryl sulfide2 was apparently the first example of a free-radical chain addition of a thiol to an acetylene. ...