Final answer:
OH- is a good nucleophile in polar solvents due to its ability to readily donate electrons, although in polar protic solvents, the solvent layer around OH- can impede its nucleophilic activity. However, OH- remains effective due to its strong electron-donating character.
Step-by-step explanation:
In polar solvents, OH- is a good nucleophile because it readily donates electrons to form bonds with electrophiles. Polar solvents, especially polar aprotic solvents, are suitable for SN2 reactions because they allow nucleophiles to remain relatively unencumbered to attack electrophilic centers. In polar protic solvents, ionic compounds like NaCl, dissolve well due to ion-dipole interactions. However, for SN2 mechanisms, the solvent layer around the nucleophile, like OH-, can prevent it from effectively approaching the electrophilic carbon. Nonetheless, OH- can still be an effective nucleophile due to its strong electron-donating character, which is not significantly hampered in the presence of polar solvents.