STRUCTURAL DEPENDENCE OF HETEROLYTIC BOND-DISSOCIATION ENERGY OF CARBON-CARBON SIGMA-BONDS IN HYDROCARBONS

The coordination of a resonance-stabilized hydrocarbon cation and anio n yielded a series of unprecedented hydrocarbons, which are susceptibl e to thermal heterolytic cleavage of carbon-carbon sigma bonds in pola r media, generating the original ions under reversible conditions. Whe n the component ions were sufficiently stabilized, some ion pairs were even isolated as solids, thus providing the first examples of hydroca rbon salts. The direct observation of the heterolysis by means of spec troscopy permitted reliable thermodynamic treatments of the observed d egree of ionic dissociation. Correlation of the free energy of heterol ysis with solvent dielectric constants and parameters of ion stabiliti es such as PKHA, pK(R+) and redox potentials revealed the importance o f the thermodynamic stabilities of ions, the degree of solvation and s teric congestion in the starting molecule as major controlling factors in the heterolysis. (C) 1998 John Wiley & Sons, Ltd.