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retro-diels-alder reaction is a form of distillation process. cyclopentadiene exists as a dimer. By distilling it and keeping it cold, slows the Diels-Alder reaction with itself after the distillation. Keeping it cold doesn't completely stop the reaction, so the cyclopentadiene must be used soon as it will reverse back to its dimer.
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Nov 2nd, 2015
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