Phase transfer catalytic reaction of n-bromobutane and sodium sulfide in a two-phase solution and its kinetics

The reaction between sodium sulfide (Na2S) and n-bromobutane (1-C4H9Br) to synthesize di-n-butyl sulfide (RSR; R: C4H9) was carried out for in an organic solvent/alkaline solution two-phase medium under phase transfer catalysis (PTC) conditions. A rational reaction mechanism and a kinetic model were satisfactorily developed by considering the reactions from which two sites of nucleophiles on a molecule displaced the organic-phase reactant. The two-film theory, which includes mass transfer and phase equilibrium of the catalysts between two phases, was employed to describe the dynamic behavior of the reaction system. In this system, the two-site active catalyst, QSQ (Q(+): (C4H9)(4)N+), which was produced from the reaction of sodium sulfide and quaternary ammonium salt, was first synthesized in the aqueous phase, and then transferred to the organic phase in preparation for further reaction. QSR was produced from the first reaction of the organic solution, and RSR was produced from the second reaction of the organic solution. Neither of these two-site active catalysts were isolated from the solution, nor were they detected from the solution during the reaction. Only the first apparent constant of the organic-phase reaction (k(app, 1)) was obtained via experimental data. Detailed investigation was made for: effect of agitation, temperature, amount of sodium sulfide, organic solvents, catalysts, amount of TBAB catalyst, amount of sodium hydroxide, volume of sodium sulfide solution, volume of organic solvent, and amount of water on the reaction rate and the conversion. The results were explained satisfactorily by considering the interaction between the reactants and the environmental species. (C) 2003 Elsevier B.V. All rights reserved.