Ammonium salts are most commonly prepared by SN2 reaction of an amine with a haloalkane. Multiple alkylations of the nitrogen atom can be problematic. Because of this, the reaction is rarely useful unless a quarternary ammonium salt (four alkyl or aryl groups attached to the nitrogen bearing the positive charge) is the desired product. Amines are reasonable bases, and thus may also cause E2 reactions of haloalkanes as well.