Used to Study Hypercoordinate Carbocations

More efficient mixing methods for the generation of reactive carbocations have been developed, most notably by Ahlberg and coworkers and Saunders et al. The former group used an ion generation apparatus consisting of a Schlenk tube attached to an NMR tube in which the carbocation is prepared in a low-temperature unit. 

Saunders method involves the codeposition of streams (molecular beams) of the starting reagents from the gas phase on a surface cooled to liquid nitrogen temperature to produce stable solutions of carbocations. - - Myhre and YannonP used it to generate carbocations in an SbFg matrix at temperature as low as 5 K for solid-state NMR spectroscopic studies. 

Various spectroscopic techniques have been applied to the characterization of carbocations as stable ions in solution and in the solid state. The techniques that have found most application in the study of hypercoordinate carbocations were developed primarily to be capable of distinguishing trivalent cations undergoing rapid degenerate rearrangements from bona fide hypercoordinate ions. In recent years, theoretical studies have become also very useful in the study of hypercoordinate carbocations. Furthermore, many properties such as chemical shifts ( H, etc.) and vibrational spectra can be accurately computed. 

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