Solvent effects of dipolar substituents in close proximity to a charged reaction centre

Abstract

Regarding the unusually good solvating properties and high dielectric constant of bulk water, an exceptional case is observed in the solvation of non-specifically solvated dipolar substituents, which are in close proximity to a charged reaction centre. The basicity of dipolar substituted trimethylamines was studied in water, acetonitrile (AN), and dimethyl sulphoxide (DMSO). The lines of force between the dipole and the charged reaction centre are evidently not transmitted significantly through the high dielectric constants of bulk water, but instead a medium more like a single water molecule. The results are consistent both on steric grounds as well as the correlation of the solvent attenuation factor (SAF) with the molecular dipole moment of water.