DMSO

Dimethyl sulfoxide (DMSO) is a polar aprotic solvent. Unlike protic solvents such as alcohols (ROH) and carboxylic acids (RCO₂H) it is termed “aprotic” since it cannot act as a hydrogen bond donor to anions like F(-). These properties, along with its high dielectric constant (47) and dipole moment (3.96 D) make it an excellent solvent for nucleophilic substitution reactions (S_N2).