Gas-phase thermolysis of sulphur compounds. Part I. Di-t-butyl disulphide

The gas-phase thermolysis of di-t-butyl disulphide was studied in a stirred-flow system using the toluene carrier technique in the temperature range 330–400 °C. The temperature dependence of the rate coefficients is given by the equation log k= 14.6 ± 0.4 –(184 ± 4) kJ mol–1/2.303RT. In a static system, the Arrhenius equation obtained was log k= 13.6 ± 0.2 –(177 ± 2) kJ mol–1/2.303RT in the temperature range 246–300 °C and initial pressures between 60 and 212 Torr. In both cases the kinetics followed a first-order law. The reaction products were mainly isobutene and hydrogen disulphide, the latter decomposing partially into sulphur and hydrogen sulphide on the surface of the glass. 5 mole % Isobutane was found in the hydrocarbon product throughout the whole temperature range, and it was as high as 13% when the static system was used. A unimolecular mechanism for the decomposition is proposed in which isobutene and hydrogen t-butyl disulphide are formed in the first step, the latter decomposing rapidly into hydrogen disulphide and isobutene in the second step.