Kinetics and Mechanism of the Reactions of S-Ethoxycarbonyl O-Ethyl Dithiocarbonate with O-Ethyl Xanthate and O-Ethyl Thiocarbonate Ions

Article abstract of DOI:10.1021/jo00211a015

The forward and back reactions of S-ethoxycarbonyl O-ethyl dithiocarbonate (1) with O-ethyl thiocarbonate (4) and O-ethyl xanthate (5) in 95percent ethanol are studied kinetically.The back reaction products are bis(ethoxycarbonyl) sulfide (3) with 5 and bis(ethoxythiocarbonyl) sulfide (2) with 4, respectively.Compound 1 reacts faster than 2 with 4, which means that the carbonyl group is more reactive than the thiocarbonyl toward 4.On the other hand, the reaction of 5 with 1 is faster than that with 3, which indicates that 5 reacts more readily with the thiocarbonyl than the carbonyl group.Two mechanisms are proposed to account for the kinetics results: one through tetrahedral intermediates (two-step reactions) and the other concerted.The reactions of 4 exibit ΔS<*> >0, whereas those of 5 show ΔS<*> <0.These ΔS values are explained by a larger solvation of 4 relative to 5 and similar degrees of solvation of transition states and substrates.The observed activation parameters do not allow discrimination between the two mechanisms.