Determining the gas-phase properties and reactivities of multiply charged ions

Approaches for analyzing kinetic and thermochemical data from the reactions of multiply charged ions are presented. A method for estimating the electr ostatic repulsion in a multiply charged ion is described followed by exampl es of the potential energy surfaces for two representative reactions of mul tiply charged ions, proton transfer and nucleophilic substitution (S(N)2), The effect of electrostatic repulsion on reaction barriers is discussed and approaches for extracting thermochemical data from kinetic results are des cribed. For reactions with small intrinsic barriers (i.e. proton transfer), considerable internal electrostatic repulsion is released at the transitio n state and multiply charged ions exhibit much greater reactivity than sing ly charged analogs. In contrast, relatively little electrostatic repulsion is released at the transition states of reactions with large intrinsic barr iers (i.e. S(N)2) and multiply charged ions with moderate charge separation s (>10 Angstrom) can exhibit reactivity that is very similar to that of sin gly charged analogs. Copyright (C) 1999 John Wiley & Sons, Ltd.