28563-38-4Relevant academic research and scientific papers
Kinetics and Mechanism of the Reactions of S-Ethoxycarbonyl O-Ethyl Dithiocarbonate with O-Ethyl Xanthate and O-Ethyl Thiocarbonate Ions
Castro, Enrique A.,Meneses, Beatriz,Santos, Jose G.,Vega, Juan C.
, p. 1863 - 1866 (1985)
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.
Kinetics and Mechanism of the Aminolysis of S-Ethoxycarbonyl O-Ethyl Dithiocarbonate and Related Pyrothiocarbonates
Castro, Enrique A.,Alvarado, Noemi E.,Pena, Sergio A.,Santos, Jose G.
, p. 635 - 642 (2007/10/02)
The reactions of S-ethoxycarbonyl O-ethyl dithiocarbonate (1), bis(ethoxythiocarbonyl) sulphide (4), and bis(ethoxycarbonyl) sulphide (5) with pyrrolidine, piperidine, and morpholine in 95percent aqueous ethanol have been subjected to kinetic study.The rate equation found for all the reactions is kobs = ko + kN, where kobs is the pseudo-first-order rate constant (amines were in excess over the substrates) and N represent the free amine.The rate law accounts for reaction schemes with zwitterionic tetrahedral intermediates, EtOC(S-)(NH+)SCXOEt and EtOC(O-)(NH+)SCXOEt, where X is O or S, formation of which from reactants is the rate-determining step.The intermediates break down to products faster than their deprotonation by the solvent or another amine molecule.This is confirmed by estimation of the rate constants involved in the schemes and evaluation of the pKa value of the intermediates.From the kN values obtained it is deduced that amines attack at the CS group of the substrate faster than at the CO group, although the nature of both the substrate and the amine could change this order of reactivity.Activation parameters are reported for all the reactions, and it was found that ΔS was lower for attack for CO compared with that at CS.This is explained in terms of higher solvation of the transition state for CO attack relative to that for CS attack.
