Proton-induced reactions of [2.2]-paracyclophane in the gas phase. A study by FT-ICR-spectrometry and DFT calculation:

The reactions of the [2-2]-paracyclophane 1 and the [2-2]-metaparacyclopane 2 in the gas phase after protonation by CI(CH4) or CI(I-C4H10) were studied by FT-ICR mass spectrometry. The ions C16H17+ produced in the external ion source of the FT-ICR instrument were transferred into the ICR cell containing the neutral reactant, and the reactions were analyzed measuring the efficiency of the transfer of a proton to a series of bases with known proton affinity and gas phase basicity as well as the efficiency of the ion-molecule reaction with ethyl vinyl ether. Both reaction types show that the ions C16H17+ produced by chemical ionization (CI) consist of two sets of isomeric ions A and B which exhibit distinctly different behavior on deprotonation and of the reaction with ethyl methyl ether. Isomer(s) A (about 65% of the ion population) react efficiently with this vinyl ether by an addition/elimination process typical of primary and secondary benzylic carbenium ions, while isomer B (about 35% of the ion populat...