Thermal Transformations of Cubane Derivatives |
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Authors: | V. G. Prokudin G. V. Lagodzinskaya V. V. Dubikhin G. M. Nazin L. B. Romanova L. T. Eremenko |
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Affiliation: | (1) Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, Moscow oblast, 142432, Russia |
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Abstract: | The thermal degradation of the cubane moiety in 1,4-cubanedicarboxylic acid, its dimethyl ester, and 1,4-dibromocubane in a condensed state were studied by calorimetry. The kinetic parameters and the composition of products, as determined by 1H and 13C NMR spectroscopy, are consistent with a biradical reaction mechanism. The presence of carboxyl groups capable of resonance conjugation stabilizes a biradical and increases the rate of isomerization of the acid and ester by a factor of 20, as compared with that of cubane. Bromine as a substituent has almost no effect on the rate of cubane thermolysis. The primary biradical is rapidly isomerized to corresponding cyclooctatetraene derivatives. A detailed reaction scheme is presented, and the relative rates of individual steps of the process are considered. |
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