Kinetics and mechanisms of gas phase elimination of ethyl 1‐piperidine carboxylate, ethyl pipecolinate, and (revisited) ethyl 1‐methyl pipecolinate

The kinetics of the gas‐phase elimination of the title compounds has been determined in a static reaction system over the temperature range of 340–420°C and pressure range of 45–96 Torr. The reactions proved to be homogeneous, unimolecular, and obey a first‐order rate law. The estimated rate coefficients are represented by the following Arrhenius expressions: Ethyl 1‐piperidine carboxylate\documentclass{article}\pagestyle{empty}\begin{document}$$ \log k_{1}({\rm s}^{-1}) = (12.61 \pm 0.11) - (191.1 \pm 1.4)\,{\rm kJ}\ {\rm mol}^{-1}(2.303\ \hbox{\bfseries\itshape{RT}})^{-1}, r = 0.9999 $$\end{document}Ethyl pipecolinate\documentclass{article}\pagestyle{empty}\begin{document}$$ \log k_{1}({\rm s}^{-1}) = (12.87 \pm 0.16) - (204.3 \pm 2.1)\, {\rm kJ}\ {\rm mol}^{-1}(2.303\ \hbox{\bfseries\itshape{RT}})^{-1}, r = 0.9998 $$\end{document}Ethyl 1‐methyl pipecolinate\documentclass{article}\pagestyle{empty}\begin{document}$$ \log k_{1}({\rm s}^{-1}) = (13.34 \pm 0.32) - (209.4 \pm 4.0)\, {\rm kJ} {\rm mol}^{-1}(2.303\ \hbox{\bfseries\itshape{RT}})^{-1}, r = 0.9992 $$\end{document}The first step of decomposition of these esters is the formation of the corresponding carboxylic acids and ethylene. The acid intermediate undergoes a very fast decarboxylation process. The mechanism of this elimination reactions is suggested on the basis of the kinetic and thermodynamic parameters. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 383–389, 2005