Gas-phase thermolysis ofN-methyl-N-phenyl-tert-butylsulfenamide and morpholinyl-tert-butylsulfenamide

Abstract

N-Methyl-N-phenyl-tert-butylsulfenamide (MPSA) and morpholinyl-tert-butylsulfenamide (MOSA) were thermolyzed in a stirred-flow reactor at temperatures of 340-390°C and pressures of 7-13 Torr, using toluene as carrier gas, at residence times of 0.3-1.3 s. Isobutene was formed in 99% yield through first-order reactions having the following Arrhenius parameters (A,s À1 , E a , kJ mol À1 ): MPSA, log A = 12.41 AE 0.02, E a = 158.8 AE 0.2; MOSA, log A = 12.91 AE 0.22, E a = 159 AE 3. It is proposed that the elimination of isobutene takes place by unimolecular reaction mechanisms involving polar, four-center cyclic transition states, forming S-unsubstituted thiohydroxylamines as coproducts. Thermochemical parameters, estimated by semiempirical AM1 calculations, are reported for the latter and for the parent molecules.