The Norbornyl Cation: A Reappraisal of its Structure Under Stable Ion Conditions

Abstract

Publisher Summary When a norbornyl derivative is dissolved in SbF 5 -HSO 3 F or a large number of related acids, an apparently long-lived ion is formed. The solutions have been subjected to many spectral studies in efforts to elucidate its structure under stable ion conditions. These include the use of ESCA (C-1s x-ray electron spectroscopy), 13 C-nmr, 1 H-nmr, and Raman spectroscopy. Under these conditions, the ion undergoes intramolecular rearrangements, which are studied by nuclear magnetic resonance (NMR), and, if it forms a stable nonclassical structure, it must exhibit a protonated cyclopropyl ring. The formation and proton exchange behavior of protonated cyclopropanes during the rearrangement of alkyl cations in similar solutions has recently been studied and these techniques have also been applied to the norbornyl problem. In addition to these probes, theoretical calculations are being made in efforts to decide upon the inherently most stable structure of the ion. These are and conclusions are derived from the study of isotope effects in solvolysis and substituent effects in stabilizing media.