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 electrostatic repulsion in a multiply charged ion is described followed by examples of the potential energy surfaces for two representative reactions of multiply 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 described. For reactions with small intrinsic barriers (i.e. proton transfer), considerable internal electrostatic repulsion is released at the transition state and multiply charged ions exhibit much greater reactivity than singly charged analogs. In contrast, relatively little electrostatic repulsion is released at the transition states of reactions with large intrinsic barriers (i.e. S(N)2) and multiply charged ions with moderate charge separations (>10 A) can exhibit reactivity that is very similar to that of singly charged analogs.
Gronert
S
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Department of Chemistry and Biochemistry, San Francisco State University, San Francisco, California 94132, USA. sgronert@sfsu.edu
D005740:Gases; D007477:Ions; D007700:Kinetics; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D055672:Static Electricity; D013816:Thermodynamics
D005740:Gases; D007477:Ions