The hydrophobic effect as a mechanistic tool

Reactions in water of species with hydrophobic surfaces are slowed by the a ddition of antihydrophobic cosolvents if the transition states involve shie lding of part of those surfaces from solvent, or speeded if the transition states are more hydrophobic than are the reactants. Using this and other to ols, some displacements have been shown to occur by single elctron transfer (SET) mechanisms, others by direct nucleophilic attack with various geomet ries. The results correlate well with the predictions of quantum mechanical calculations.