Mechanisms of water elimination and other degradations of 2‐hydroxy‐5‐ketobornane cations in the gas phase

Abstract

The mechanisms of water elimination in 2-hydroxy-5-ketobornanes have been investigated and compared with those in borne01 and isoborneol in order to ascertain whether and how such processes are affected by incorporation of a remote second functional group of lower ionization energy. Analysis of metastable ion peak shapes and specZfic labelling with "H and =O are employed as methods for differentiating between individual reaction paths. In addition, those degradation reactions which give rise to the most prominent fragments and pattern differences in the mass spectra of the epimeric keto alcohols were sautinized. The elimination of water is shown to exhiiit entirely different features due to the presence of the carbony1 group.The other most important degradation reactions all proceed by hydrogen transfer from the hydmxyl group onto the charged product and concomitant loss of the hydroxyl oxygen in a neutral entity. The results are interpreted in terms of initial charge radical localization on the carbonyi group initiating the relevant chemical reactions. Peak shape analysis proves a very valuable, and at times the only useful way to distinguish individual reactions.