Why is acetone used in SN2 reactions?
Acetone used in
Polar aprotic solvents are polar enough to dissolve the substrate and nucleophile, but they do not participate in hydrogen bonding with the nucleophile.
The lack of hydrogen bonding means that the solvation shell of a polar aprotic solvent around the nucleophile is quite weak. The nucleophile has little trouble attacking the substrate.
Nucleophiles are more nucleophilic in polar aprotic solvents.