Hydride abstraction from 1,3,5-cycloheptatriene by gaseous carbenium ions, as studied by Fourier transform ion cyclotron resonance kinetics and deuterium labeling

The gas-phase interaction of protonated acetone and tert-butyl cations with 1,3,5-cycloheptatriene was studied by Fourier transform ion cyclotron resonance (Fr-ICR) mass spectrometry. In addition to proton transfer giving C7H9+ ions, hydride abstraction from cycloheptatriene giving C7H7+ ions was observed. Deuterium labeling 9 experiments combined with the determination of the reaction kinetics excluded the formation of C-7-H-7(+) ions by consecutive proton transfer and H-2 expulsion under these conditions. The kinetic isotope effect measured for the hydride transfer channel was found to be in the range 1.65 +/- 0.1, very close to that known to operate during hydride transfer from simple alkylbenzenes to t-C4H9+ ions. Copyright (C) 2003 John Wiley Sons, Ltd.