Chapter 14. Chemical Transformations II: Redox Reactions

Summary

Many important chemical transformations involve oxidative and reductive steps, also called redox reactions. The thermodynamics of these electron-transfer changes are discussed in terms of the Gibbs free energy changes and the corresponding reduction potentials, leading to the Nernst equation formulation. With this result, the spontaneity of redox reactions under environmental conditions (e.g., pH 7) is examined. Although many redox transformations are thermodynamically favored, they prove to be kinetically limited. The general sequence of steps leading to electron transfer is described, and the relative reactivities of structurally-related compounds are examined to assess what the likely rate-limiting processes involve. The importance of electron-transfer mediators in many environmental systems is illustrated.