Gas‐phase thermolysis of sulfur compounds. Part IV. n ‐propyl allyl sulfide

The pyrolysis of n ‐propyl allyl sulfide has been studied in static and stirred‐flow systems at temperatures between 270 and 400°C. Propene and 2,4,6‐triethyl‐1,3,5‐trithiane were the only reaction products. The order of the reaction was 0.99 ± 0.05 at 377°C. The first‐order rate coefficients followed the Arrhenius equation\documentclass{article}\pagestyle{empty}\begin{document}$$k{\rm (s}^{- 1} {\rm) = 10}^{{\rm 11}{\rm .52} \pm {\rm 0}{\rm .16}} {\rm exp[(- 157} \pm {\rm 2) kJ/mol/R}T]$$\end{document}The rate coefficients and the product distribution remained unchanged when cyclohexene was used as carrier gas. A molecular mechanism involving a six‐centered cyclic transition state is proposed to explain the present results. This mechanism is further supported by the pyrolysis of 4‐thia‐5‐dideutero‐1‐heptene at 377°C, where only 3‐deuteropropene is formed. The kinetic deuterium isotope effect had a value of 2.6 ± 0.3 at this temperature. The results are compared with those obtained in the pyrolysis of n ‐butyl allyl sulfide previously reported.