ION MOLECULE REACTIONS OF TERT-BUTYL CATION WITH TERTIARY ALCOHOLS

The tert-butyl cation (tBu+) is widely used as a chemical ionization reagent ion, for which it is often assumed that simple proton transfer to neutral substrates is the dominant reaction. Mass-analyzed ion kinetic energy (MIKE) spectrometry and the collisionally activated decomposition (CAD) of ions corresponding to the adducts R'O(H)R+ formed from mixtures of ROH and R'OH (R = tBu, R' = tBu or 1-methylcyclopentyl, and their deuterated analogues) show a much more complicated pattern of reactivity, which is mirrored in the bimolecular reactions of tBu+ with R'OH in the Fourier transform ion cyclotron resonance (FT-ICR) technique. Production of R'+ in the CAD and FT-ICR experiments is accompanied by isotopic exchange between the alkyl groups, which implicates ion-neutral complexes as accessible intermediates in addition to the covalent adduct ions. A unified pathway for MIKE spectrometry, CAD, and FT-ICR regimes is presented, involving terbody complexes of the form [cation water alkene] as well as two-body complexes of the form [cation alcohol].