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Kinetics of the thermal dimerization and isomerization of cis, trans ‐1,5‐cyclooctadiene in the gas phase and of related reactions. A simple algorithm to determine the rate constants of competing first‐ and second‐order reactions
Author(s) -
Leitich J.
Publication year - 1979
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.550111204
Subject(s) - gas phase , chemistry , arrhenius equation , physics , kinetics , isomerization , thermodynamics , activation energy , catalysis , quantum mechanics , organic chemistry
In the gas phase, cis , trans ‐1,5‐cyclooctadiene ( \documentclass{article}\pagestyle{empty}\begin{document}$ {\mathop 1\limits_\sim} $\end{document} ) undergoes a unimolecular rearrangement to cis , cis ‐1,5‐cyclooctadiene ( \documentclass{article}\pagestyle{empty}\begin{document}$ {\mathop 2\limits_\sim} $\end{document} ) and bimolecular formation of dimers \documentclass{article}\pagestyle{empty}\begin{document}$ {\mathop 3\limits_\sim}-{\mathop 5\limits_\sim} $\end{document} $\end{document} . The Arrhenius parameters are E A = 135.7 ± 4.4 kJ mole −1 and log( A /sec −1 ) = 12.9 ± 0.6 for the first reaction and E A = 66.1 ± 6.0 kJ mole −1 and log[ A /(liter mole −1 sec −1 )] = 5.5 ± 0.8 for the second reaction. Using thermochemical kinetics, the first reaction is shown to proceed via a rate determining Cope rearrangement of \documentclass{article}\pagestyle{empty}\begin{document}$ {\mathop 1\limits_\sim} $\end{document} to cis 1,2‐divinylcyclobutane ( \documentclass{article}\pagestyle{empty}\begin{document}$ {\mathop 6\limits_\sim} $\end{document} ), E A = 136.2 ‐ 4.4 kJ mole −1 and log( A /sec −1 ) = 13.0 ± 0.6. The corresponding back reaction, \documentclass{article}\pagestyle{empty}\begin{document}$ {\mathop 6\limits_\sim}{\rightarrow}{\mathop 1\limits_\sim} $\end{document} , which was investigated separately, shows E A = 110.2 ± 1.2 kJ mole −1 and log( A /sec −1 ) = 10.9 ± 0.2. The heat of formation of \documentclass{article}\pagestyle{empty}\begin{document}$ {\mathop 6\limits_\sim} $\end{document} is determined to 188 ± 5.5 kJ mole −1 . The mechanism of formation of dimers \documentclass{article}\pagestyle{empty}\begin{document}$ {\mathop 3\limits_\sim}-{\mathop 5\limits_\sim} $\end{document} is discussed. To allow the formal analysis of the kinetic problem, a simple algorithm to obtain the rate constants of competing first‐ and second‐order reactions was developed.