Esther Quintanilla

Thermodynamic Stabilities of Carbocations

Publisher Summary This chapter addresses the quantification of the concept of “stability”. Thermodynamic criteria have been applied to rank carbenium ions on the basis of their intrinsic stabilities—that is, stabilities in the absence of solvent. Both experimental and computational data have been used. It discusses the relationship between the intrinsic thermodynamic stability of these species and their reactivity in solution, from both the thermodynamic and the kinetic points of view. Relevant structural features of these species, as revealed by experimental or computational methods data, have been reviewed. Quantum mechanical calculations at the highest possible levels (within our computational capabilities) have been performed on most of the species. The scope of this chapter is limited to a relatively small number of ions that illustrate some representative examples of structural effects. The “low resolution” overview of the gas-phase stabilities of a variety of carbenium ions shows that they are by no means exotic data unrelated to solution reactivity. On the contrary, they are the fundamental factor determining the relative stabilities of the same species in solution.