BASICITY, NUCLEOPHILICITY, AND NUCLEOFUGALITY IN THE ELIMINATION SUBSTITUTION-REACTIONS OF BETA-PHENYLMERCAPTOETHYL PHENOLATES IN DMSO-ETHANOL MEDIA

Kinetic studies have been performed on the base-promoted 1,2-eliminati on reactions of a series of beta-phenylmercaptoethyl phenolates with p otassium ethoxide in EtOH-DMSO media, yielding phenyl vinyl sulfide. T he E2 mechanism was indicated by the absence of H/D exchange in the su bstrate when the reaction in EtOD-DMSO-d6 containing EtO- was carried to partial completion. The Bronsted coefficient values (beta(LG), effe ct of nucleofugality on reaction rate) of ca. 0.30 and ca. 0.98 were e stimated for the reaction in pure DMSO and ethanol, respectively. Comp arison of the results with reported reactions of substrates of similar structure revealed the important role of the phenyl group on sulfur, the leaving-group nucleofugality, and the medium basicity, in controll ing the reaction pathways (elimination versus substitution).