Formation and stability of carbocations and carbanions in water and intrinsic barriers to their reactions

Abstract

Lifetimes in water as short as 10(-11) s have been determined for carbocations and carbanions by referencing the rate of their reaction with solvent species to that for the appropriate "clock" reaction, and equilibrium constants have been determined as the ratio of rate constants for their formation and breakdown. Rate-equilibrium correlations for these organic ions are often poor and sometimes even defy the simple generalization that reactivity increases with decreasing stability. This seemingly confusing body of data can be understood through consideration of the both the Marcus intrinsic barrier and the thermodynamic driving force to reaction of these organic ions.