TETRAHEDRAL STRUCTURES OF UNEXPECTED STABILITY . ON DISTINGUISHING AND RANDOMIZATION MECHANISMS IN MASS SPECTRAL FRAGMENTATION OF SUBSTITUTED CYCLOPENTADIENOLS

Pentaphenylcyclopentadienol molecular ions show partial hydrogen scrambling, as well as partial phenyl scrambling, before they fragment in the mass spectrometer. A major route for decomposition is the stepwise loss of the elements of aryl and CHO, to give a labeled C4Ph4- +. Labeling experiments suggest a tetrahedral symmetry for this species at some point before its further decomposition. The p-fluoro-labeling experiments suggest that the phenyl carbon skeleton remains intact, while deuterium labeling shows scrambling of hydrogens on the skeleton. The observation of this species after so unlikely a mode of formation, coupled with previous observations, offers the possibility that the tetraphenyltetrahedrane radical cation may possess unusual stability in mass spectral decompositions, like the tropylium ion in other systems. © 1969, American Chemical Society. All rights reserved.