Base-Induced Solvent Switches in Acid-Base Reactions

摘要

Proton-transfer reactions in aqueous environments have been the subject of numerous studies in solution chemistry as they play a central role in many chemical[1]-[8] and biochemical processes.[9]-[12] Modern discussions of acid-base reactions that involve proton transfer between Br?nsted acids and Br?nsted bases[13] have evolved from the seminal studies of Eigen[14], [15] and Weller.[16] Eigen's review of the field[14] outlined the general kinetic approach for acid-base reactions in aqueous solution (Figure 1 a). Eigen discussed three reaction branches that lead to proton transfer and ultimately resulting in chemical equilibrium, namely direct proton exchange between acid and base, acid dissociation to solvent with subsequent proton scavenging by the base (protolysis), and water hydrolysis by the base with subsequent neutralization of the acid by the hydroxide anion. This model proved to be extremely useful for analysis of the relaxation kinetics of acid-base reactions that occur on the micro- to millisecond timescale.