Carceplex

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A carceplex is a hinged, box-like molecule from the carcerand family that can be closed around a reactive species. Closing reagents react with the container to trap the precursor of a reactive intermediate (or the intermediate itself) inside, and those reagents do not react with the trapped species. This isolation lets chemists study the spectroscopy and crystal structure of reactive intermediates in relative isolation, especially for compounds that tend to dimerize, like cyclobutadiene.