The Effect of S-Substituent Variation on the Pyrolysis of Xanthates of Primary Alcohols

A study of the pyrolysis of a series of S-substituted xanthates of cyclohexanemethanol was undertaken to determine the effect of variations in the nature of the S-substituent on the course of the pyrolysis of xanthates. Xanthates with the following S-substituents were prepared by standard reactions and pyrolyzed at 240°: n-hexyl, 2-phenylethyl, benzyl, phenacyl, and diphenylmethyl. Evidence is presented that supports the view that a competitive homolytic pathway becomes more significant as the stability of the free radical derived from the S-substituent increases. At the two extremes, the S-hexyl xanthate yields 90% methylenecyclohexane and no cyclohexanemethanol whereas the S-diphenylmethyl xanthate yields only 25% alkenes (methylenecyclohexane and 1-methylcyclohexene) along with 65% cyclohexanemethanol.