Reactions in “sacrificial” solvents

Abstract

The involvement of organic solvents in redox reactions and their influence on the efficiency and “greenness” of the desired chemical transformation are critically reviewed. Some representative examples are presented on the co-oxidation and co-reduction of widely used solvents (alcohols, ethers, nitriles, amides, sulfoxides, hydrocarbons, dense CO₂), and on the impact of these frequently hidden reactions. The transformation of the solvent may be limited to its unintended consumption leading to an increase in the E-factor, but it may also play a critical role in the reaction investigated and lead to false interpretation of reaction mechanisms. In fact, the approach of using a “sacrificial” solvent as a part of the oxidizing system may be an attractive—but surely not a green—alternative in synthetic chemistry. Finally, the crucial but often unrecognized role of the solvent in stabilizing or destabilizing catalytic metal nanoparticles is discussed. Surface redox reactions involving the solvent can be decisive for switching between heterogeneous and homogeneous catalytic pathways.