Intrinsic gas-phase acidity and electrophilicity of model heterocations and carbocations relative to pyridine: Adduct formation versus α- or β-(proton transfer) elimination

Ion/molecule reactions of gaseous silylium ions (Me3Si+, Cl3Si+, Br3Si+, and bridgehead 3,5,7-trimethyl-1,3,5,7-tetrasilaadamant-1-yl cation), carbocations (tBu+, iPr+, Et+, (MeO)2CH+, CCl3+, CF3+, Ph+, PhCH2+, C7H7+, and 3,5-dimethyl-1-adamantyl cation), and the dicoordinated boron cation B(OMe)2+ with pyridine were investigated. Three competitive channels: (a) electrophilic addition that forms stable adducts, (b) direct β-elimination that leads to proton transfer, or (c) α-elimination that leads to the transfer of a substituent directly attached to the charge center were identified.