Dipolar Aprotic Solvents

• Published in: Solvent Effects in Chemistry p. 1
• Main Authors: Stairs, Robert A, Buncel, Erwin
• Format: Book Chapter
• Language: English
• Published: United States John Wiley & Sons 2016; John Wiley & Sons, Incorporated; John Wiley & Sons, Inc
• Edition: 2nd Edition
• Subjects: Chemistry & Chemical Engineering; dimethyl sulfoxide; dipolar aprotic solvents; Industrial Chemistry & Chemicals; proton transfer processes; solvent effects; thermodynamic transfer functions
• ISBN: 1119030986; 9781119030980
• DOI: 10.1002/9781119044307.ch6

Dipolar aprotic solvents came into prominence in the 1960s, with the discovery that the rates of a number of reactions of the S N 2 type, and some other reactions as well, were very greatly enhanced, by factors up to 109, when carried out in solvents such as dimethylformamide and dimethyl sulfoxide as compared to common hydroxylic solvents such as water or ethanol. Dimethyl sulfoxide (DMSO) is highlighted as the prototypical dipolar aprotic solvent, though this chapter presents comparisons with other dipolar aprotic solvents. Approaching solvent effects from the viewpoint of thermodynamic transfer functions allows one to examine in a systematic manner the outcome of medium change, from a protic to a dipolar aprotic reaction medium, in terms of structure and charge distribution in reactants, transition states, and products. Some of the largest rate enhancements due to solvent change have been observed for proton transfer processes.