The pyrolysis of trimethylene sulfide. A unimolecular decomposition

The kinetics of decomposition of trimethylene sulfide to ethylene and thioformaldehyde was investigated in a single‐pulse shock tube using the «relative rate» technique. The extent of reaction was measured in the reflected shock regime from 860° to 1170°K, but experimental difficulties limited the useful data to the temperature range of 980°–1040°K. The first‐order rate constant was found to be k = 10 13.0 exp (−48,200/ RT ) sec −1 . This result sets an upper limit of 50 kcal/mole for the standard enthalpy of formation of CH 2 S, with 35 kcal/mole as a more likely value. The isomerization of cyclopropane to propene was used for the reference reaction; in turn, this was checked, in a relative rate experiment, against the pyrolysis of cyclohexene.