The thermal unimolecular isomerization of cis‐hepta‐1,3‐diene

The reversible isomerization of cis ‐hepta‐1,3‐diene to cis ‐2‐ trans ‐4‐heptadiene via a 1,5 hydrogen shift has been investigated kinetically at nine temperatures in the range of 475° to 531°K. Equilibrium is reached near 94% reaction. Some cis ‐2‐ cis ‐4‐heptadiene is also formed, but at a rate some 60 times slower than the cis , trans isomer. A least‐squares analysis of the data yielded the Arrhenius equation for the isomerization of the cis ‐hepta‐1,3‐diene:\documentclass{article}\pagestyle{empty}\begin{document}$$ {{\log k_1 } \mathord{\left/ {\vphantom {{\log k_1 } {\sec ^{ - 1} = {{(11.110 \pm 0.087) - ([33,210 \pm 200]{\rm cal mole}^{ - {\rm 1}} )} \mathord{\left/ {\vphantom {{(11.110 \pm 0.087) - ([33,210 \pm 200]{\rm cal mole}^{ - {\rm 1}} )} \theta }} \right. \kern-\nulldelimiterspace} \theta }}}} \right. \kern-\nulldelimiterspace} {\sec ^{ - 1} = {{(11.110 \pm 0.087) - ([33,210 \pm 200]{\rm cal mole}^{ - {\rm 1}} )} \mathord{\left/ {\vphantom {{(11.110 \pm 0.087) - ([33,210 \pm 200]{\rm cal mole}^{ - {\rm 1}} )} \theta }} \right. \kern-\nulldelimiterspace} \theta }}} $$\end{document}Possible errors in the equilibrium constant measurements are discussed, and employing an equilibrium constant calculated by using group additivity estimates together with the values of k 1 , we obtained for the reverse reaction\documentclass{article}\pagestyle{empty}\begin{document}$$ {{\log k_2 } \mathord{\left/ {\vphantom {{\log k_2 } {\sec ^{ - 1} = (11.1 \pm 0.15) - ([35,800 \pm 300])}}} \right. \kern-\nulldelimiterspace} {\sec ^{ - 1} = (11.1 \pm 0.15) - ([35,800 \pm 300])}}{{{\rm cal mole}^{ - {\rm 1}} )} \mathord{\left/ {\vphantom {{{\rm cal mole}^{ - {\rm 1}} )} \theta }} \right. \kern-\nulldelimiterspace} \theta } $$\end{document}where\documentclass{article}\pagestyle{empty}\begin{document}$$ \theta = 2.303RT $$\end{document} .